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IEEE Transactions on Antennas and Propagation
Journal Prestige (SJR): 1.309
Citation Impact (citeScore): 5
Number of Followers: 81  
 
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ISSN (Print) 0018-926X
Published by IEEE Homepage  [228 journals]
  • IEEE Transactions on Antennas and Propagation

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      Abstract: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • IEEE Transactions on Antennas and Propagation

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      Abstract: These instructions give guidelines for preparing papers for this publication. Presents information for authors publishing in this journal.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Institutional Listings

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      Abstract: Presents a listing of institutions relevant for this issue of the publication.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Editorial Reflections From the New Editor-in-Chief

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      Authors: Konstantina S. Nikita;
      Pages: 5 - 6
      Abstract: Season’s Greetings! It is with true delight and great privilege that I am writing this editorial to present the January 2023 issue of the IEEE Transactions on Antennas and Propagation (TAP). Since I took over as the Editor-in-Chief in October 2022, I have worked together with the Editorial Board and the IEEE staff to ensure a smooth transition. I am particularly thankful to my predecessor, Prof. Danilo Erricolo, for all the advice and support he has offered me over the past few months.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Development of a Ka-Band Non-Regular Multibeam Coverage Antenna

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      Authors: Enrica Calà;Marco Baldelli;Alfredo Catalani;Esteban Menargues;Giovanni Toso;Piero Angeletti;
      Pages: 7 - 17
      Abstract: This article describes the development of a novel Ka-band array fed reflector antenna based on a passive multifeed-per-beam (MFPB) beamforming network (BFN) to realize multiple shaped beams for broadband satellite communications applications. The feeding array is organized in non-regular overlapped sub-arrays (OSAs) in order to generate contiguous shaped beams in two polarizations with a single reflector. The main novelty is the generation of the non-regular multibeam coverage with differently shaped beams which equalizes the traffic demand per beam as generated by a non-uniform distribution of users over the satellite coverage. The entire feeding array is organized in two interleaved and partially overlapped groups of sub-arrays, one per polarization, to better satisfy the beam overlap requirements and isolation between co-polarized beams. A complex BFN has been developed as a monolithic component through a 3-D additive manufacturing (AM) technique. The test campaign demonstrated the suitability of the design approach and the accuracy of the selected manufacturing technique for the Ka-band frequencies, with a good correlation between measured and simulated results.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • 220 GHz High-Gain Substrate Integrated Antennas With Low Fabrication Cost
           Based on Higher Order Mode and PCB Technology

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      Authors: Peng Wu;Kebin Liu;Zhongjun Yu;
      Pages: 18 - 28
      Abstract: In millimeter-wave (MMW) and terahertz (THz) bands, the operation frequency is high and there are challenges in fabrication and microassembly processes, bringing high-accuracy requirements and high manufacturing cost. In this article, high-gain substrate integrated antennas with low fabrication cost are presented for MMW/THz applications. The basic antenna consists of two parallel TE201 resonant cavities and is directly fed by a grounded coplanar waveguide (GCPW). Radiation slot apertures are modified to increase aperture radiation efficiency and improve radiation patterns and gain. The antenna scheme is analyzed and a 220 GHz $2times2$ slot array antenna is developed as an example. To further improve the antenna gain with low fabrication cost and low feeding network loss, the basic antenna is explored to feed a modified dielectric plate lens. The high-gain scheme and design flowchart are provided. Both basic and improved structures are fabricated by normal single-layer printed circuit board (PCB) technology and high antenna gains are achieved. The measured peak gain of the basic antenna and the antenna with dielectric plate lens are 13.5 and 20.2 dBi, respectively. The measured return losses are better than 10 dB from 192 to 247 GHz. The antennas have advantages of simple antenna feeding structure, low fabrication cost, wide bandwidth, and high gain.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Circularly Polarized Broadside Beam Radiated From a Large, Low-Profile
           Metaloop Antenna

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      Authors: Hisamatsu Nakano;Tomoki Abe;Junji Yamauchi;
      Pages: 29 - 38
      Abstract: The area within a loop antenna can be used for inserting additional components (such as mounting hardware) if this does not cause the antenna characteristics to degrade. This article discusses a circularly polarized (CP) metaloop antenna that has a loop circumference of ${C} _{mathrm {LOOP}}= 1 lambda _{text {g}}= nlambda _{0}$ with $n>1$ , thereby creating a large area within the loop, where $lambda _{text {g}}$ ( $= 2~pi /beta $ ) and $lambda _{0}$ ( $= 2~pi /k_{0}$ ) are the guide wavelength of the current on the loop and the free-space wavelength, respectively. Values for the propagation phase constant within the range of $-1 < beta /k_{0} < 0$ are used in this article. It is found that metaloop antennas for $n = 3$ , 4, and 5 generate a CP broadside beam (axial beam) with gain bandwidths (GBWs) of approximately 6%, 5%, and 4%, respectively. The VSWR across the GBWs is less than two and the axial ratio is less than 3 dB. The radiation efficiencies for $n=3$ , 4, and 5 are approximately 48%, 69%, and 83%, respectively. When a conducting disk (as a generalization for the presence of additional components) is inserted into these metaloop antennas, the antenna -haracteristics are not degraded until the disk and the metaloop are in close proximity (proximity coupling occurs).
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Metasurface Antennas Design: Full-Wave Feeder Modeling and Far-Field
           Optimization

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      Authors: Jean Cavillot;Modeste Bodehou;Christophe Craeye;
      Pages: 39 - 49
      Abstract: This article addresses the optimization of the radiation pattern of surface-wave (SW)-based metasurface (MTS) antennas. Those antennas are considered a promising alternative to parabolic reflectors and phased arrays due to their extremely low profile and their ability to provide high gain, shaped beams and multibeams. However, pattern synthesis with MTS antennas is very challenging because of the single active control point and the need to control surface and leaky waves through the MTS. An accurate optimization of the radiation pattern, along with the sidelobe level requires full-wave modeling of the feeding structure, including its coupling with the MTS. MTS synthesis methods existing in the literature usually approximate the feeder model, and neglect its coupling with the MTS. Such approximation may lead to more than 1 dB error in the predicted antenna directivity. This article presents a technique for optimization of the far-field pattern, built on a Method of Moments (MoM) analysis tool in which the MTS coupling with the feeder, a coax probe, is fully considered. The MTS is modeled as an arbitrarily shaped, spatially modulated electric sheet impedance in a layered medium. At each optimization iteration, the complexity of the underlying analysis is $mathcal {O}(text {N}log text {N})$ owing to the use of a fast Fourier transforms (FFT)-based acceleration. The effectiveness of the method is demonstrated through the optimization of MTSs radiating a pencil beam and a conical beam with orbital angular momentum (OAM).
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A High Aperture Efficiency Endfire Antenna Based on Spoof Surface Plasmon
           Polaritons

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      Authors: Qingfeng Fu;Hao Ni;Guo Qing Luo;Lei Zhu;Leilei Liu;
      Pages: 50 - 57
      Abstract: A high aperture efficiency endfire antenna based on odd mode spoof surface plasmon polaritons (SSPPs) is proposed in this article. First, a pair of symmetrical SSPPs transmission lines (TLs) is applied to an endfire antenna. To realize an endfire antenna, the SSPPs TLs are supported by a balun with a 180° phase shifter, and this makes each pair of SSPPs units works as a dipole. Next, we study the dispersive curve of this dipole-shaped SSPPs unit and get its relationship between phase constant and frequency. Then, the Hansen–Woodyard condition is used to get a maximum gain at endfire direction. Moreover, in order to excite a radiation into the free space, we compose a tapered structure with this pair of SSPPs TLs. As a result, an endfire antenna with zero tilted angle operates in the frequency range of 9–11 GHz and achieves an average gain of 11.51 dBi. In addition, this SSPPs antenna realizes a high aperture efficiency up to 13.26 dBi $/lambda _{0}^{2}$ . The simulated and measured results are in good agreements over the operating band. The proposed SSPPs endfire antenna holds a low profile, small aperture, and it is promising for application in satellite and radar communication systems.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Wideband High-Gain Omnidirectional Biconical Antenna for Millimeter-Wave
           Applications

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      Authors: Zhi-Yi Zhang;Kwok Wa Leung;Kai Lu;
      Pages: 58 - 66
      Abstract: A novel omnidirectional biconical antenna for millimeter-wave (mm-wave) wireless communications is investigated. It is loaded by an annular metal lens that consists of rotationally symmetric annular metal plates (MPs). A nearly uniform $E$ -field distribution can be obtained at the radiating aperture across a wide frequency range, giving a wideband high-gain omnidirectional antenna. The operating principle and design flowchart of the lens are given. To validate the idea, a Ka-band vertically polarized prototype was fabricated. Both its measured −10 dB impedance and 3 dB gain bandwidths are 43.9% (25.6–40.0 GHz), with the maximum measured gain given by 9.2 dBi. As compared with the conventional biconical antenna, our antenna can obtain a higher gain by ~4 dB across the entire impedance passband.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Optically Transparent Metasurface Radome for RCS Reduction and Gain
           Enhancement of Multifunctional Antennas

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      Authors: Trung D. Ha;Liang Zhu;Nabeel Alsaab;Pai-Yen Chen;Jay L. Guo;
      Pages: 67 - 77
      Abstract: In this article, we theoretically propose and experimentally demonstrate a compact, optically transparent metasurface radome with asymmetric electromagnetic absorption for making low-radar cross section (RCS) and gain-enhanced multifunctional antennas. The proposed unseeable metasurface has a bilayer structure consisting of periodically patterned and unpatterned transparent conductive films separated by a thin acrylic layer. Such a bilayer metasurface is highly reflective when illuminated by microwave from one side, while exhibit a high absorption when illuminated from the other side. Moreover, when the optically transparent, weather-proofing bilayer metasurface acts as a radome, it can greatly enhance the gain and reduce RCS of the solar panel-integrated microstrip antenna without affecting the performance of optical devices (e.g., photovoltaic panels, flat panel displays, or light emitting devices). We provide the analytical formulation and design guidelines for the bilayer metasurface and the integrated cavity antenna. Our experimental results show that the realized gain of the microstrip antenna can be increased by 6.1 dBi and its RCS can be reduced by more than 20 dB around the operating frequency of 8.1 GHz. The proposed low-profile, flexible, hydrophobic, and optically transparent bilayer metasurface may be beneficial for many applications, including the next-generation radomes, self-powered 5G/6G base stations, satellite communication (CubSat), and other compact, multifunctional RF and microwave modulus integrated with optical sensors, lidar, displays, and solar panels.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Tapered Graded Index Lens Antenna With Enhanced Penetration for Near-Field
           Torso Imaging

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      Authors: Seyed Mohammad Hadi Mousavi;Sasan Ahdi Rezaeieh;Amin Darvazehban;Beadaa Mohammed;Azin S. Janani;Amin M. Abbosh;
      Pages: 78 - 88
      Abstract: A tapered graded index (GRIN) lens antenna that aims at enhancing electromagnetic penetration into human torso by generating focused planar near-field radiation is presented. The antenna is composed of a four-layer lens excited by a modified slot antenna. Each layer of the lens case is filled with fabricated mixtures of engineered materials that have specific relative permittivity values. The exciting antenna is made compact by utilizing meandered feed lines and substrate folded technique. The number of layers of the lens and the specification of each layer are determined by minimizing the generalized reflection coefficient of the antenna. A focused plan-wave radiation is achieved by tapering the lens based on the theory of total internal reflection. The study of $E$ -field quality inside the torso demonstrates that the proposed lens successfully converts spherical wave radiation into a local plane-wave radiation, resulting in 11 dB improvement in wave penetration inside the torso compared to the body-matched antenna (without lens). The measured results show that the antenna operates over a wide band from 0.43 to 1.85 GHz (125% fractional bandwidth), which is a merit for the torso imaging application. Furthermore, the antenna has the physical size of 110 $times 110times48$ mm3, corresponding to $0.15times 0.15times 0.06lambda _{0}^{3}$ , where $lambda _{0}$ is the wavelength at the lowest working frequency. The results indicate that the antenna accomplishes 4.9 dB (209% improvement) stronger wave penetration inside the torso compared to other existing GRIN lens antennas.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Broadband Millimeter-Wave Antenna in Package With L-Probed E-Shaped Patch
           Covering 57 GHz to 71 GHz

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      Authors: Tae Hwan Jang;Kyung Pil Jung;Chul Soon Park;
      Pages: 89 - 98
      Abstract: In this work, millimeter-wave antenna-in-package (AiP) with L-probed E-shaped patch covering from 57–71 GHz is proposed. By combining the characteristics of E-shaped and L-probe patch, broadband $2times 2$ and $4 times 4$ array AiP is designed based on a new antenna element covering from 57–71 GHz. Assuming that the $2times $ 2 array is placed in the first quadrant, the $4times $ 4 array will be made by mirroring in the 2nd, 3rd, and 4th quadrants, respectively, so the antenna elements should not be positioned outside the first quadrant. The proposed AiP shows 6.9 dBi peak measured gain for the antenna element with 3.2 dB fluctuation for the 57–71 GHz frequency band. In addition, the proposed antenna shows an impedance-matching characteristic of at least −8.3 dB in a given band. The fabricated $2times $ 2 AiP was connected via bond wire to a four-element phased array transmit beamformer IC and the beam-forming characteristics were verified.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Bandwidth and SNR of Small Receiving Antennas: To Match or Not to Match

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      Authors: Kamal Sarabandi;Menglou Rao;
      Pages: 99 - 104
      Abstract: In this article, the merits of impedance matching a small antenna to the receiver’s impedance are investigated. The goal is to demonstrate that a small antenna with low radiation resistance and high input reactance, when directly connected to a high-impedance (high-impd) receiver, can provide significantly better signal-to-noise ratio (SNR) than when it is matched to a standard 50 $Omega $ input-impedance receiver. Theoretical analysis is first carried out to compare the noise performance of the two receivers by deriving analytical expressions for the SNRs of the receivers. It is shown that the SNR of a high-impd receiver is superior to that of an impedance-matched receiver. Subsequently, two test receivers are constructed and characterized to verify the theoretical calculations. The measured SNR of the high-impd receiver is 11.4 dB higher than that of the matched receiver, even though the first-stage amplifier used in the high-impd receiver has a much worse noise performance compared to that used in the matched receiver. This study demonstrates that matching a receiving antenna to the load impedance is not always the optimal solution as far as the SNR is concerned. Furthermore, unlike a small antenna with a narrow-band matching circuit, a small antenna connected to a high-impd receiver without any matching network provides a very wide bandwidth and overcomes the gain-bandwidth limitation of small antennas. This discovery breaks new ground in the realization of compact wideband systems for low-frequency communications.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Low-Cost and Highly Accurate Behavioral Modeling of Antenna Structures by
           Means of Knowledge-Based Domain-Constrained Deep Learning Surrogates

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      Authors: Slawomir Koziel;Nurullah Çalık;Peyman Mahouti;Mehmet A. Belen;
      Pages: 105 - 118
      Abstract: The awareness and practical benefits of behavioral modeling methods have been steadily growing in the antenna engineering community over the last decade or so. Undoubtedly, the most important advantage thereof is a possibility of a dramatic reduction of computational expenses associated with computer-aided design procedures, especially those relying on full-wave electromagnetic (EM) simulations. In particular, the employment of fast replacement models (surrogates) allows for repetitive evaluations of the antenna structure at negligible cost, thereby accelerating processes such as parametric optimization, multi-criterial design, or uncertainty quantification. Notwithstanding, a construction of reliable data-driven surrogates is seriously hindered by the curse of dimensionality and the need for covering broad ranges of geometry/material parameters, which is imperative from the perspective of design utility. A recently proposed constrained modeling approach with knowledge-based stochastic determination of the model domain addresses this issue to a large extent and has been demonstrated to enable quasi-global modeling capability while maintaining a low setup cost. This work introduces a novel technique that capitalizes on the domain confinement paradigm and incorporates deep-learning-based regression modeling to facilitate handling of highly-nonlinear antenna characteristics. The presented framework is demonstrated using three microstrip antennas and favorably compared to several state-of-the-art techniques. The predictive power of our models reaches remarkable 2% of a relative rms error (averaged over the considered antenna structures), which is a significant improvement over all benchmark methods.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A TM11 High-Order Mode Leaky Wave Antenna

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      Authors: Gian P. Carrara;Constantinos L. Zekios;Stavros V. Georgakopoulos;
      Pages: 119 - 130
      Abstract: A novel leaky-wave antenna (LWA), which operates at the $TM_{11}$ high-order mode, is proposed. This LWA achieves a 4.6 times higher gain than the traditional TE10-based LWAs. An analytical formulation is derived, which shows that a $TM_{11}$ -based LWA couples more energy to free space through an appropriately designed slot than traditional TE10-based LWAs. Simulations are used to compare the performance of our proposed $TM_{11}$ -based LWA with a similar LWA that operates at its fundamental TE10 mode. Specifically, it is shown that our $TM_{11}$ high-order mode LWA achieves 6.67 dB higher gain than a TE10-mode LWA that operates at the same frequency. Also, a $TM_{11}$ -mode LWA is designed to mitigate the open-stopband (OSB) problem. This design achieves a fan beam with a maximum gain of 15.4 dBi and a scanning elevation range of 18° (through the broadside direction) in a bandwidth of 2 GHz. Prototypes of our LWA designs are manufactured using a cost-effective additive manufacturing method (i.e., selective laser melting), and their performance is measured. The measurements exhibit good agreement with simulations, thereby validating the proposed designs.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Zeroth-Order Slot-Loaded Cap-Shaped Patch Antenna With Omnidirectional
           Radiation Characteristic for UHF RFID Tag Design

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      Authors: Shin-Yi Ooi;Pei-Song Chee;Eng-Hock Lim;Jen-Hahn Low;Fwee-Leong Bong;
      Pages: 131 - 139
      Abstract: The zeroth-order resonance of a compact patch structure is explored for designing a metal-mountable tag antenna in the United States (US) ultrahigh-frequency (UHF) radio frequency identification (RFID) passband. This zeroth-order resonator (ZOR) structure comprises a cap-shaped patch loaded with two L-shaped slots. Also, the patch is coupled to the ground through two inductive stubs which provide enough parasitic reactance to support the zeroth-order resonance. The proposed single-element ZOR can generate sufficient antenna impedance for achieving a conjugate match with the RFID chip impedance. Good omnidirectional radiation characteristic with vertically polarized fields can be attained in the azimuth plane when the tag antenna is placed on a metallic surface. The proposed tag antenna’s realized gain at 915 MHz is −1.382 dB [effective isotropic radiated power (EIRP) 4 W]. A stable read distance of ~15 m is obtainable with even spatial coverage in the entire azimuth plane. The resonance frequency of the proposed tag does not vary much with the object being tagged.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Broadband Low-Profile Circularly Polarized Radial Line Slot Antenna

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      Authors: Matthieu Bertrand;Mauro Ettorre;Guido Valerio;Matteo Albani;M. Casaletti;
      Pages: 140 - 150
      Abstract: This article presents a circularly polarized corporate-fed radial-line slot antenna (CF-RLSA) operating in Ka-band and realized in low-cost, low-profile printed circuit board (PCB) technology. The radiating aperture is fed by a corporate feed network based on a broadband pillbox-like circular transition. The proposed feeding system results in a 67% gain bandwidth improvement compared to classical center-fed radial line slot antenna (RLSA) designs. Pattern stability versus frequency is also achieved. The bandwidth improvement provided by the corporate-feed topology is analytically derived for the general case of circular apertures with uniform amplitude illumination. This predicted improvement is confirmed by measurements. The prototype is optimized using a dedicated numerical tool, then fabricated and characterized. A good agreement is obtained between simulated and measured gain bandwidths, with a demonstrated relative bandwidth of 6.9% at 29 GHz for a maximum gain of 35.5 dBi and a 260 mm diameter for the radiating aperture.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Wideband Absorbing Metasurface for Improving Axial Ratio of a Compact
           Archimedean Spiral Antenna

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      Authors: Aritra Roy;K. J. Vinoy;Noham Martin;Stéphane Mallégol;Cedric Quendo;
      Pages: 151 - 158
      Abstract: A wideband absorbing metasurface is proposed to improve the circularly polarized response of a 1–18 GHz low-profile Archimedean spiral antenna. The metasurface consisting of surface-mounted resistors between metallic patches in a circular arrangement is placed on the opposite side of the antenna substrate. After analyzing the unit cell behavior under an equivalent three-conductor transmission line, a concentric arrangement of the metasurface under the spiral is proposed. This metasurface is designed to absorb the edge-reflected waves to improve the circularly polarized response of the antenna below 6 GHz. The antenna substrate with the metasurface is placed above a flat conductor that makes an overall antenna height of 5 mm. After numerical investigations, a prototype is fabricated and characterized. The measured right-hand circularly polarized gain is positive above 2 GHz with a maximum gain of approximately 8.7 dBic at 10.6 GHz. An axial ratio (AR) better than 3 dB is observed above 1.125 GHz. The benefits of the metasurface compared to a commercially available absorbing material are highlighted, and its usefulness to design a compact spiral antenna is presented.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Phased Array With Pattern Shaping and Scan Loss Reduction for Millimeter
           Waves

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      Authors: Ralph M. van Schelven;Waqas H. Syed;Giorgio Carluccio;Kostas Doris;Anton de Graauw;Andrea Neto;Daniele Cavallo;
      Pages: 159 - 168
      Abstract: In this work, we investigate antenna architectures to implement dual-mode operation in phased array designs. Planar slot antenna elements are used in array configuration, in combination with artificial dielectrics layers (ADLs) located in the close proximity of the array, to achieve pattern shaping. The artificial dielectric superstrate supports the propagation of leaky waves that can be optimized to enhance the gain in a specific angular region or to enlarge the array field of view. By controlling the amplitude and phase of the antenna elements, the radiation patterns can be combined to realize either wide or narrow beams. This concept present advantages for both millimeter-wave (mm-wave) communication and radar applications. A design of a four-element array fabricated in standard printed circuit board (PCB) technology validates the feasibility of the dual-mode operation. The measured results also show good agreement with simulations.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Half-Mode Cavity Backed Hybrid Array Antenna Using Substrate Integrated
           Waveguide (SIW) Technology

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      Authors: Abu Hena Murshed;Md. Azad Hossain;Nguyen Khac Kiem;Nguyen Hoang Hai;Md. Anwar Hossain;Eisuke Nishiyama;Ichihiko Toyoda;
      Pages: 169 - 179
      Abstract: This article proposes a hybrid array antenna where a cavity-backed antenna is used jointly with a patch antenna using half-mode substrate integrated waveguide technology (HMSIW) to reduce antenna size. This hybrid structure consists of a flexible Rogers RO4003C substrate ( $epsilon_{{r}} =3.55$ ) showing linearly polarized TE101 mode where the cross-polarization level (XPL) is less than −12 dBi. An inset feed has been utilized to excite the main cavity resonator, and later by proximity coupling, the parasitic patch is also excited in TE101 mode. By further dividing the outer patch, four new cases of antenna have emerged, and comprehensive investigations on their parameters based on simulation have been presented. It paints an upgrade of the antenna’s performance. As per simulations, further dividing of the patch helps to bring out positive changes in the antenna’s performance by escalating gain, bandwidth (BW), and efficiencies while also lessening XPL, sidelobe levels (SLLs), and associated loss up to a satisfying level. The proposed antenna is then fabricated and experimentally validated in its theoretical analysis. A couple of experimentally validated parameters make this fabricated sample suitable for wireless application and maintain good agreement with numerical simulation. CST Microwave Studio and HFSS carried out the associated numerical simulation.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Broadband Electromagnetic-Transparent Antenna and Its Application to
           Aperture-Shared Dual-Band Base Station Array

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      Authors: Rong Chao Dai;Huafeng Su;Sheng Jie Yang;Jun-Hui Ou;Xiu Yin Zhang;
      Pages: 180 - 189
      Abstract: In this article, a broadband electromagnetic (EM)-transparent element is proposed for aperture-shared dual-band base station array application. The array consists of the proposed low-band (LB) transparent element and a $4times $ 4 broadband antenna array operating at high-band (HB). The LB radiator is a dual-polarized dipole, loaded with dielectric blocks both on the top and bottom sides. The LB element is placed right above the center of HB array. Since the dielectric-loaded radiator achieves broadband transparent characteristics in HB, the HB array can radiate with almost no blockage from the LB element. The mechanism of the characteristics is studied by using an equivalent circuit. Experimental results show that the blockage effect of the LB radiator on the broadband HB element is reduced by loading dielectric blocks. For verification, a dual-band antenna array operating at 0.76–1.03 GHz and 3.4–5 GHz bands is fabricated and measured. Compared with the isolated HB array, the peak gain deterioration of the aperture-shared array is below 0.8 dB. On the directions within the half-power beamwidth (HPBW), variation of the gain is under 1.8 dB. The results demonstrate that the dielectric-loaded radiator can be used in a multi-band base station array to restore the pattern of a broadband HB array.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Single Motor-Controlled Mechanically Reconfigurable Reflectarray

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      Authors: Zhongyao Cao;Yue Li;Zhijun Zhang;Magdy F. Iskander;
      Pages: 190 - 199
      Abstract: In this article, a mechanically reconfigurable 1-D reflectarray actuated by a single motor is proposed. The elements are designed as metal tubes that are lifted by the ejectors. To achieve continuous phase growth in a limited space, the discontinuity of the Archimedean spiral is utilized. Then, a novel drive mechanism is constructed to transfer the power of the motor to each element. The combination of the Archimedean spiral cam and the follower effectively converts the rotation of the shafts to the linear motion of the element. In conjunction with the timing pulleys and timing belts, the Archimedean spiral cams generate a periodic changing phase gradient over time. The whole structure is supported by low-cost acrylic plates with fasteners. The main parts are composed of standard components and the overall structure is easy to realize. The reflectarray at normal incidence offers a beam steering range from −60° to 60° in one dimension at 5 GHz. The beam coverage test demonstrates a maximum improvement in the received signal level of 16 dB in the multipath environment. This work provides a new solution to the design of mechanically reconfigurable reflectarrays.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Multi-Channel Implantable Cubic Rectenna MIMO System With CP Diversity in
           Orthogonal Space for Enhanced Wireless Power Transfer in Biotelemetry

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      Authors: Vikrant Kaim;Neeta Singh;Binod Kumar Kanaujia;Ladislau Matekovits;Karu P. Esselle;Karumudi Rambabu;
      Pages: 200 - 214
      Abstract: For wireless power transfer (WPT), an implantable cubic rectenna multi-input-multi-output (MIMO) system (CRMS), operating in dual industrial, scientific, and medical (ISM) frequency bands of 2.45 and 5.8 GHz, is presented as a receiver ( $R_{x}$ ). CRMS is evolved to the proposed biocompatible full-package cubic rectenna (FPCR) by including the power and data management circuit modules. The dual frequency bands differentiated by orthogonal circular polarization (CP) in a spatial quadrature would serve as propagation channels for power, data, and control signals. Four dual-branch rectifiers are designed using both distributed and lumped elements on the backside of individual antenna elements. To demonstrate the feasibility of the proposed work as an integrated system for WPT, the structures are fabricated individually, where the transmitter ( $T_{x}$ ), which is an external antenna, and rectifiers are tested in free space and FPCR in a custom-made canonical phantom. After validation of individual measurements, power delivery from the $T_{x}$ to the FPCR is conducted experimentally to measure the integrated system’s radiofrequency (RF)-dc total conversion efficiency (TCE). The FPCR is designed to receive low RF power ( $P_{mathrm {RF}}$ ) of 0 dBm, where a single cubic rectenna element (CRE) provides dc power ( $P_{mathrm {DC}}$ ) of 0.26 and 0.33 mW at 2.45 and 5.8 GHz, respectively. Thereafter, the interconnection of CREs in a series/parallel configuration improved $P_{mathrm {DC}}$ to
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Optimization of Multibeam Antennas Employing Generalized Joined Coupler
           Matrix

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      Authors: Charles A. Guo;Y. Jay Guo;He Zhu;Wei Ni;Jinhong Yuan;
      Pages: 215 - 224
      Abstract: Currently, there is increasing interest in analog multibeam antennas whose beams can be flexibly steered to arbitrary directions. In a previous paper, we presented the theoretical framework for synthesizing individually steerable multiple beams using generalized joined coupler (GJC) matrices. The synthesis method was to optimize the array excitation vectors to approximate known distributions. In this article, we present a more robust optimization method to optimize the multibeams directly in order to control the half-power beamwidth, the sidelobe levels, and nulls for mitigating system interference. The effectiveness of the proposed method is demonstrated by numerical examples. We reveal how the quality of the multiple beams is inherently determined by the dimensions of the GJC matrix. Experimental results of a $3,, times10$ Nolen-like GJC matrix are presented for the first time to validate the proposed method in realizing low sidelobe multibeams.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Modeling and Analysis of the Active Surface System for the Large
           Single-Dish Sub-mm Telescope

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      Authors: Jingjing Gao;Hairen Wang;Yingxi Zuo;Ji Yang;Xuepeng Chen;Mingzhu Zhang;Xiaoling Zhang;Wensheng Cheng;Jingsi Liang;Tianzhe Zhang;
      Pages: 225 - 235
      Abstract: Enlarging antenna diameter while maintaining an accurate reflective surface is important in the development of next-generation single-dish sub-mm telescopes. In this article, we propose an emulation and optimization method of the active surface system (EOMASS) for large single-dish sub-mm telescopes. The proposed method involves three main steps: 1) building an active surface system model (ASSM) based on the whole finite element model (FEM) of the large single-dish sub-mm telescope, which includes the main reflector, realistic adjustment models of actuators, backup structure and so on; 2) emulating the reflective surface deformation compensation under gravity based on the initial distribution of the actuators with the ASSM, in consideration of the manufacturing error of panels; and 3) further optimizing the number and distribution of actuators based on the illumination function, and predicting the performance of the sub-mm antenna due to the limited number of faulty actuators. As an application example, a 60 m single-dish sub-mm telescope is analyzed under gravity with the proposed EOMASS. The results demonstrate that the proposed EOMASS is an effective and advanced method, providing a feasible precision design of the active surface system for a large single-dish sub-mm telescope.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Low-Profile True-Time-Delay Beamsteerable Leaky-Wave Antenna for Satellite
           Applications in the K Band

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      Authors: Elham Baladi;Gursimran Singh Sethi;Hervé Legay;Sean Victor Hum;
      Pages: 236 - 249
      Abstract: In this work, a low-profile center-fed leaky-wave antenna (LWA) is proposed, which combines the full-space beam-scanning capabilities of transmitarrays and the low-profile nature of LWAs. A true-time-delay (TTD) phase-shifting mechanism is used, where a variable length stripline inside the unit cell yields more than 540° of phase range. The 2564-element array generates a pencil beam that may be designed for steering to arbitrary angles. A gain of 27.8 dBi is measured at broadside, while this value measures 22.2 dBi at the representative off-broadside angle of $theta _{0} = 30^{circ} $ at the design frequency of 19.5 GHz. The proposed antenna is low profile, with a thickness of 1.6 mm (approximately $lambda /10$ at the design frequency) mounted on top of a radial feed waveguide possessing an 8 mm (approximately $lambda /2$ ) height.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Focal-Plane Arrays With Improved Scan Capabilities

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      Authors: Aleksei Dubok;A. Bart Smolders;
      Pages: 250 - 262
      Abstract: This article investigates the limits of focal-plane array (FPA) technology by studying a double-reflector antenna system with wide-angle scan capabilities. The proposed reflector configurations are analyzed in terms of effective isotropic radiated power (EIRP) maximization, minimization of the required total number of array elements for a wide-scan range, and the highest number of simultaneously active array elements of the phased-array feed. Presented configurations have capabilities to operate in the scan range up to ± 30° in azimuth (±35 beamwidths scan) and ± 3° in elevation. It has been demonstrated how different optimizations could allow to build systems with varying performance in terms of the key operation parameters, such as array size, EIRP, and the number of active array elements. A detailed analysis is provided that demonstrates the potential applicability of this concept in future millimeter-wave (mm-wave) applications.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Survey of Antenna Miniaturization Technology Based on the New Mechanism
           of Acoustic Excitation

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      Authors: Wanqing Li;Du Li;Kaixiang Zhou;Qixiang Fu;Xuelin Yuan;Xiangwei Zhu;
      Pages: 263 - 274
      Abstract: Antenna miniaturization technologies have always been the focus of antenna research. In recent years, mechanical antennas whose size does not depend on the electromagnetic (EM) wavelength have attracted researchers’ attention. Acoustically excited antennas (AEAs), as a kind of mechanical antenna, can achieve reciprocal transmission and reception. AEAs utilize internal charge and magnetization oscillations of piezoelectric materials and magnetoelectric (ME) composite materials, respectively, to radiate EM waves, which enables the size of the antenna to be related to the wavelength of the acoustic wave, reducing the size of the antenna by 4–5 orders of magnitude over conventional antennas. Additionally, it is expected to achieve breakthrough application changes in the fields of mobile low-frequency antennas, portable shortwave antennas, and chip-based microwave antennas. In this article, the theory of AEAs is summarized and different modeling and measurement studies of AEAs are described in detail. Finally, the challenges of AEAs research are elaborated and future research on AEAs is prospected.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Study on Electromagnetic Scattering Characteristics of 4-D Antenna
           Arrays

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      Authors: Zihao Li;Chunmao Xie;Feng Yang;Yikai Chen;Shi-Wei Qu;Jun Hu;Shiwen Yang;
      Pages: 275 - 287
      Abstract: A theoretical study on electromagnetic scattering mechanism of 4-D antenna arrays is performed for the first time. First, the scattering fields of one antenna element within an infinite 4-D array are derived under periodic boundary conditions. In order to estimate the scattering performances of 4-D antenna arrays, numerical models of the scattering fields are then established based on the traditional scattering pattern multiplication theory. Moreover, an effective time-domain full-wave approach is proposed for the scattering cross section (SCS) simulation of 4-D arrays. Finally, to verify the feasibility for SCS reduction through 4-D arrays, the differential evolution (DE) algorithm is adopted to synthesize a 14-element microstrip patch antenna array for the optimization of radiation and scattering performances. Numerical results show that 4-D arrays are capable of scattering the incident waves in both space domain and frequency domain simultaneously, thus accomplishing remarkable in-band SCS reduction.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Cavity-Backed Double H-Slot Antenna With IPMC Flaps for Designing
           Frequency-Switchable On/In-Metal Semi-Active Tag

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      Authors: Jen-Hahn Low;Pei-Song Chee;Eng-Hock Lim;
      Pages: 288 - 298
      Abstract: A frequency-switchable semiactive tag antenna that can perform well on both the on- and in-metal platforms is proposed. A double H-slot antenna has been employed for designing the tag, and it can be easily made using a copper-clad polyimide film. The proposed antenna structure has a backing metallic cavity, which has made the read performance very robust even being used for the in-metal platform. To achieve the frequency reconfiguration, the ionic polymer–metal composite (IPMC) actuators are coated with metal, and they are tactfully integrated with a double H-slot antenna for changing its shape. The IPMC flaps can be actuated with a low operating voltage for switching the tag antenna across the U.S. and EU radio frequency identification (RFID) passbands. A water-embedded substrate that consists of a polydimethylsiloxane (PDMS) container filled up with water has also been employed for miniaturizing the antenna. Good maximum read ranges (> 10 m) have been achieved for all cases.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • On the Maximum End-Fire Directivity of Compact Antenna Arrays Based on
           Electrical Dipoles and Huygens Sources

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      Authors: Alexandre Debard;Antonio Clemente;Alessio Tornese;Christophe Delaveaud;
      Pages: 299 - 308
      Abstract: This article investigates the superdirectivity limits of end-fire linear arrays based on closely spaced radiating elements. First, directivity upper bounds have been derived analytically in the case of Huygens-source- and electrical-dipole-based arrays using spherical wave expansion (SWE). The fundamental bounds are derived when the interelement spacing $d$ tends to 0 and as a function of the number of the elements ( $P$ ) composing the array. Furthermore, the complex excitation coefficients associated with end-fire arrays of $P$ infinitesimal Huygens sources and electrical dipoles are synthesized as a function of $d$ to achieve maximum directivity. For this purpose, synthesis procedures based on SWE and array theory are used. When $d$ tends to 0, the numerical results are in excellent agreement with the proposed upper bounds. The maximum superdirectivity approaches a value of P $^{2}+$ 2 $P$ and $P^{2} + P - 1/2$ , respectively, in the case of Huygens sources and electrical dipoles. A numerical method to estimate the antenna gain, when the arrays are optimized in terms of directivity, is also provided. The theoretical results are then successfully validated through electromagnetic simulations in the case of half-wavelength-dipole-based arrays as a function of $P$ and $d$ . Three prototypes are designed and experimentally characterized as well to demonstrate the proposed analysis.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Polarization Reconfigurable 3D Printed Dual Integrated Quadrifilar Helix
           Antenna Array Embedded Within a Cylindrical Dielectric Mesh

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      Authors: Youssef Tawk;Joseph Costantine;
      Pages: 309 - 317
      Abstract: This article presents a polarization reconfigurable dual integrated quadrifilar helix antenna array that is embedded within a cylindrical-shaped mesh of dielectric material. The entire structure is 3-D-printed and equipped with grooves to support the eight radiating elements and accordingly enforce the helical pitch and orientation. The dual antenna array, acting as one, features double fractional bandwidth (i.e., 30%) while exhibiting polarization reconfigurability by switching between left-handed and right-handed circular polarization states. More specifically, the proposed structure operates over the span of frequencies between 1.7 and 2.3 GHz while ensuring a circularly polarized behavior. The polarization reconfigurability is obtained by changing the phase excitation of the eight helical arms. Accordingly, a dedicated feeding network is proposed to achieve the required phase reconfiguration. A prototype is fabricated and tested as a proof of concept, where the measured results agree well with the simulated data. The 3-D-printed fabricated prototype reconfigures its circularly polarized behavior over the entire operating bandwidth with a maximum measured realized gain of 6.4 dBic, an axial ratio that varies between 0.5 and 2.5 dB, and cross-polarization levels of at least 20 dB along the direction of maximum radiation.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Wideband Gain Enhancement of MIMO Antenna and Its Application in FMCW
           Radar Sensor Integrated With CMOS-Based Transceiver Chip for Human
           Respiratory Monitoring

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      Authors: Wensong Wang;Zhongyuan Fang;Kai Tang;Xixi Wang;Zhou Shu;Zhenyu Zhao;Yuanjin Zheng;
      Pages: 318 - 329
      Abstract: A novel compact multiple-input multiple-output (MIMO) antenna is proposed with wideband gain enhancement. It consists of two identical antenna elements spacing about half wavelength. First, a 1-to-2 Y-shaped power divider with wideband anti-phase outputs is designed to feed two modified Vivaldi radiators. The currents on the two radiating surfaces keep the same direction in a wideband to increase radiation without being canceled. Second, the square-ring unit cell is analyzed to form metasurface, placed in the front of the radiator. It can guide the forward electromagnetic (EM) radiation while reducing the backward radiation. Third, a U-shaped slot is etched between the two modified Vivaldi radiators. It is approximated as an effective electrically small dipole radiator. Such arrangement further effectively enhances the radiation performance in the direction of the main lobe and destructively interferes with the sidelobe radiation. These features make the antenna far-field radiation pattern reshaped. Thereby, the gain is improved in a wide bandwidth. Meanwhile, the MIMO antenna diversity performance is analyzed with low mutual coupling. Wideband gain enhancement contributes to improve the detection capability of the frequency modulated continuous wave (FMCW) radar sensor. As a proof of concept, the proposed MIMO antenna prototype is fabricated. The measured impedance bandwidth ranges from 11.5 to 21.3 GHz [59.76% fractional bandwidth (FBW)] with isolation of $ge 24.92$ dB. The gain is up to 10.6 dBi, the radiation efficiency is 88.01%–90.02%, and the envelope correlation coefficient (ECC) is $le 0.00122$ . Integrated with the transceiver chip fabricated on the 65 nm CMOS process, the proposed MIMO antenna is applied in the FMCW radar sensor. The t-st system is built up, and the experiments on different breathing conditions are conducted for different human subjects. The proposed MIMO antenna could reduce measurement error, thereby improving measurement accuracy for human respiratory monitoring.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Design of Highly Directive GRIN MS Lens Integrated DFHA for Deep Tissue
           Biomedical Imaging

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      Authors: Shubhadip Paul;Nilesh Kumar Tiwari;Mohammad Jaleel Akhtar;
      Pages: 330 - 341
      Abstract: A novel highly directive gradient refractive index (GRIN) metasurface (MS) lens integrated dielectric-filled horn antenna (DFHA), with an enhanced signal penetration and spatial focusing, is developed for the effective monitoring and detection of tumors deep inside the body. For this purpose, two novel GRIN MS lens topologies are proposed, where an optimized refractive index distribution along with the lens aperture is generated using an improved analytical formulation. In the first lens configuration, the core layer (CL) is sandwiched between two similar impedance matching layers (IMLs) on each side. In the second configuration, the CL is still surrounded by two IMLs on both sides, but one of the IMLs, in this case, is improved to avoid the requirement of an additional dielectric layer between the lens and the biological tissue. All the layers of the MS lens are based on an array of especially designed square ring-shaped unit cells. The proposed MS lens-based DFHA enhances the signal penetration by a maximum of 12 dB at 100 mm penetration inside the torso compared to the case without a lens. It also facilitates better spatial resolution due to the presence of an MS lens, which shrinks threefold the 3 dB beamwidth at 100 mm inside the torso than that of the DFHA without an MS lens. The proposed GRIN MS lens integrated DFHA is fabricated and tested on a realistic torso phantom to evaluate the tumor detection capability deep inside the torso. The simulation and experimental results show that the proposed GRIN MS lens-based DFHA can effectively be employed for tumor detection with high resolution deep inside the body.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Low-Cost and Low-Profile Electronically Programmable Bit Array Antenna
           for Two-Dimensional Wide-Angle Beam Steering

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      Authors: Zheng Xing Wang;Han Qing Yang;Feng Zhai;Jun Wei Wu;Qiang Cheng;Tie Jun Cui;
      Pages: 342 - 352
      Abstract: An electronically programmable bit array antenna (PBAA) is designed with a low profile ( $0.09lambda _{0}$ at 11 GHz) and 2-D wide-angle beam steering. The planar PBAA is composed of 8 $times8$ elements, and each of them can be individually addressed through the meticulously designed dc bias. By controlling two PIN diodes and four varactor diodes embedded, the PBAA element provides a maximum phase shift of 337.5° and 16 (4 bit) phase coding states with a 22.5° regular interval. The design is verified through simulations and measurements. The experimental results of the fabricated sample exhibit a broadside gain of 16 dBi, corresponding to the radiation efficiency of 33.1%, and 3 dB gain bandwidth of 11.8%. The sidelobe and cross-polarization levels of the broadside beam are below −19.6 and −30 dB, respectively. Moreover, the main beam is capable of scanning in the range of ±60° $times$ ±40°, and the gain fluctuations in E- and H-planes are less than 3.6 and 3 dB, respectively. The design provides flexible 2-D beam-scanning capability while being low cost, low profile, low complexity, and low power consumption, which will benefit various applications with sensing and wireless communication through electromagnetic (EM) waves.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Close-Packed Quad-Element Triple-Band-Notched UWB MIMO Antenna With
           Upgrading Capability

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      Authors: Shailesh Jayant;Garima Srivastava;
      Pages: 353 - 360
      Abstract: A close-packed 4-port multiple-input multiple-output (MIMO) antenna with three notched bands (NBs) is designed for ultra-wideband (UWB) applications. The presented antenna contains four monopole antenna elements (AEs) with rectangular radiators, each fed by an L-shaped microstrip line. The compact size of $35.9times 35.9times0.8$ mm is attained by cropping the lower axis of the antenna and optimization. The isolation greater than 19 dB is accomplished by the orthogonal direction of AEs and cross-shaped decoupling structure (CSDS). The designed antenna can realize wireless local area network (WLAN) and X-band NBs by etching two C-shaped slits from each radiator and Worldwide Interoperability for Microwave Access (WiMAX) NB by introducing an L-shaped slit in the ground. By placing these NBs in appropriate positions, their efficiencies are decreased for their better rejection. The value of $vert text{S}_{mathrm {ii}}vert < -10$ dB is from 3.2 to 10.8 GHz (except for three NBs). Also, the 4-port MIMO antenna is upgraded to a 16-port MIMO antenna by arranging the four identical 4-port MIMO antennas side by side with a small gap of 8 mm. The upgraded antenna gives bandwidths from 3.38 to 10.56 GHz with three NBs, isolation >20.9 dB, and size $79.8times79.8$ mm2, which is appropriate for future wireless communications.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Nonuniform Amplitude Transmitarray for Multibeam Including Near-Field
           Focusing

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      Authors: Chang-Hyun Lee;Jeong-Hae Lee;
      Pages: 361 - 367
      Abstract: This article presents a nonuniform amplitude transmitarray for a multibeam that includes near-field focusing, based on a frequency selective surface (FSS). Each cell on the FSS is fed by a slot array and its feeding magnitude is adjusted by the slot position. The phase sets required for near-field focusing and far-field steering are controlled by the cell size of the FSS located above each slot. To confirm the performances of the antenna, a multibeam antenna for beam focusing and steering is designed. The required phase and amplitude of each cell are simply calculated and optimized by the principle of superposition. Finally, a $6 times 4$ array prototype antenna operating at 5.8 GHz is realized, and its characteristics are measured. The antenna can simultaneously focus on a near-field spot and radiate in the desired far-field direction. The measured and simulated results are found to be in good agreement.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • High-Efficiency Modulation and Harmonic Beam Scanning in Time-Modulated
           Array

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      Authors: Gang Ni;Chong He;Yanchang Gao;Jingfeng Chen;Ronghong Jin;
      Pages: 368 - 380
      Abstract: A general high-efficiency time-modulated module and harmonic beam scanning time-modulated array (TMA) are proposed and investigated in this article. By introducing the periodically controlled phased shifters, a significant improvement on theoretical overall efficiency and transmitted bandwidth can be realized in harmonic beam scanning. Then an equivalent cascade structure of the general modulation module is proposed for RF circuit simplification and practicability in actual applications. Theoretical derivation and simulation results show that increased efficiency, 100% feeding network efficiency, and theoretical overall efficiency tending to 100% without consideration of insertion loss can be achieved with the increase of the phase-shifter states when only a single sideband is utilized. Compared to the existing state-of-the-art harmonic beam scanning TMAs, the proposed TMA exhibits a much higher overall efficiency while keeps a similar hardware complexity. Additionally, with acceptable increase of circuit complexity less than existing works, similar level of the wide transmission bandwidth can also be achieved. To experimentally verify the feasibility of the proposed general design, a 4-bit time-modulated module with reconfigurable states and the corresponding 8-element harmonic beam scanning TMA are fabricated and tested. The experiments on signal transmission and harmonic beam scanning demonstrate the effectiveness of power loss reduction and improvement in transmitted bandwidth with the increase of modulation phase states.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Development of an Equivalent Circuit Model for the Design of Array of
           Electrically Small Antennas

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      Authors: Zahra Esmati;David A. Powell;Michael C. Skipper;Michael D. Abdalla;J. Scott Tyo;
      Pages: 381 - 392
      Abstract: In this article, we present a fully parameterized circuit model of an array antenna that relates antenna performance and field coupling to the physical parameters of the elements as represented through a circuit model. We demonstrate that the simplified model can be used as a surrogate for full-wave modeling during the initial optimization steps in array design. The model accounts for mutual coupling between array elements both through the feeding network and through free space. We present a method to calculate the mutual coupling between elements in the array antenna that is parameterized in terms of the size and location of the individual elements, and these circuit models provide excellent agreement with the scattering parameters calculated by the full-wave numerical model. The model is applied to the analysis of a specific built array configuration, and we demonstrate that the simplified circuit model can have strong predictive effects for designing arrays of electrically small antennas (ESAs) and predicting their ultimate performance by comparing with numerical and limited experimental measurements. The study is motivated by high power electromagnetic (HPEM) applications, where arrays of densely space elements can help reduce the antenna size necessary to radiate extremely large power signals.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Frequency Multiplexing Patch Antenna Array for Space Selectable
           Microwave Heating

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      Authors: Chennan Li;Xianqi Lin;Xinmi Yang;Zhang Wen;Changsong Liang;
      Pages: 393 - 401
      Abstract: Space-selectable microwave heating is a new trend of customized heating at present and in the future. Controllable antenna array (CAA) can effectively achieve space-selectable heating, which has drawn wide attention. In this article, a novel CAA approach of frequency multiplexing patch antenna array (FMPA) is proposed, with which the constituted patch elements have totally different resonant frequencies and each patch element exclusively takes charge of the heating task for certain subarea of entire planar area under heating. An all-metal four-element FMPA is designed as an example. It is integrated with a metal chamber where the target heating area is enclosed. Simulation results verify that the proposed FMPA has the function of independent space-selectable heating. Then, a controllable microwave heating system is built for the subsequent heating experiment. The experiment shows that, after the corresponding patch element being activated, the coverage ratio of each target heating subarea is more than 90%, and the error ratio is less than 1.5%. The proposed CAA technique of the FMPA enjoys vast potential in customized heating applications that has higher requirements for resolution of the subareas under heating. Its advantages include low cost, low loss, and high space utilization rate.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Efficient Semi-Analytical Method for the Analysis of Large Finite
           Connected Slot Arrays

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      Authors: Alexander J. van Katwijk;Andrea Neto;Giovanni Toso;Daniele Cavallo;
      Pages: 402 - 410
      Abstract: We present an efficient method for the analysis of finite connected slot arrays in the presence of stratified media. The formulation is based on a spectral method of moments, where only one basis function is considered for each array element and one for each slot edge. An expression for the mutual impedance is derived in terms of a double spectral integral. Asymptotic extraction techniques are employed to largely reduce the computation time of one of the spectral integrals. For the other integral, when a guided wave contribution dominates the mutual coupling between two array elements, the result can be approximated as the residue of the spectral polar singularity, providing a closed-form solution of the coupling for elements at electrically large distances. The complete method enables simulations of entire finite arrays with hundreds or even thousands of elements in minutes. The same structure would require impractical computation time when analyzed with general-purpose commercial software. The method allows estimating the performance of finite connected arrays. This is particularly relevant because wideband connected arrays are known to exhibit higher edge effects compared to narrowband arrays, due to the high interelement mutual coupling.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Scan-Loss Compensation for Full-Azimuth Multi-Facet Phased Array Antennas

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      Authors: Stanislav Ogurtsov;Zhe Song;Diego Caratelli;
      Pages: 411 - 421
      Abstract: An approach to compensate scan losses displayed by full-azimuth multifacet phased arrays is proposed in this article. This approach is based on a constructive superposition of scanned beams from adjacent array panels resulting in enhanced composed coverage. Said constructive superposition is achieved by coordinating the insertion phase shifts applied at the array element level. Special attention is given to panel arrays arranged in equilateral triangle and square prisms. The benefits of the proposed beamforming approach are validated by full-wave simulations, as well as passive antenna measurements taken on physical prototypes. The achieved improvement in equivalent isotropically radiated power (EIRP) excessively compensates for the experienced scan loss and reaches 6 dB at the maximal scan angles. An additional advantage of the developed methodology consists in the mitigation of the composed beam squint at wide scan angles.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • An Optically Transparent Hybrid Mechanism Metasurface for Wideband,
           Wide-Angle and Omnidirectional Scattering Suppression

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      Authors: Yan Xi;Wen Jiang;Kun Wei;Tao Hong;Shuxi Gong;
      Pages: 422 - 432
      Abstract: Metasurface provides an efficient method to regulate wave propagation in multiphysics fields ranging from light waves, electromagnetic (EM) waves, and acoustic waves. Considering the versatile demands in practical scenarios, the essential challenge is to design the metasurface with spectral compatibility to satisfy the various applications. Here, we proposed an optically transparent hybrid mechanism metasurface (HMM) incorporating absorption, polarization conversion, and phase cancellation mechanisms for wideband, wide-angle, and omnidirectional scattering suppression performance. The unit cell integrates absorption and polarization conversion capabilities by etching the indium tin oxide (ITO) film into the specific structure, exhibiting wideband ( $7.44-31.31$ GHz), wide-angle ( $!< 45^{circ }$ ), high-efficiency ( $!ge 90$ %), and omnidirectional co-polarized scattering suppression performance. Moreover, the phase cancellation mechanism is implemented by distributing the unit cell and its mirror structure in the chessboard configuration, which provides cross-polarized reflection reduction capability for the HMM. Therefore, the HMM achieves a significant total radar cross section (RCS) reduction by integrating multiple scattering suppression mechanisms. Eventually, the simulated and measured results indicate that the proposed HMM can realize more than 10 dB total monostatic and bistatic RCS reduction within 7.49-32.23 and 7.46-30.55 GHz, respectively. In addition, good specular and omnidirectional RCS reduction capabilities are also obtained. Furthermore, the HMM also presents good optical transparency, which is attributed to the high transmittance of the polyethylene terephthalate (PET) substrates and the ITO films.-The proposed strategy has potential application in the multifunctional stealth design of stealth platforms.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Method of Designing a Planar Scan Angle Enhancing Metalens Featuring
           Lossless Wide Scanning at mmWave

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      Authors: Suho Chang;Youngno Youn;Dongseop Lee;Daehyeon Kim;Kyoungchun Kweon;Wonbin Hong;
      Pages: 433 - 442
      Abstract: For the first time, a method to design a planar scan angle enhancing lens with minimum beam distortion for automotive radar at millimeter-wave is presented. The proposed lens is not only advantageous regarding its planar topology but also offers a solution to the chronic problem surrounding planar phased array antenna and planar lenses: scan loss. In this article, ray optics and ray transfer matrix are applied to Galilean lens configuration from which the concept of scan enhancement and compensating parameters are conceived. The basic idea of compensating lies in re-focusing the portion of the beams and suppressing transmission at extreme angles. Visual analysis of the wave refraction and designing of the lens system is conducted using 2-D ray-tracing code. Full-wave simulation validates the effectiveness of the proposed idea by extending the limited scan range of the phased array antenna from 45° to 58° with gain fluctuation below 1.1 dB at E-band. The radiation efficiency is calculated to be 0.86 at 76.5 GHz. Furthermore, the proposed lens system is fabricated using low-temperature co-fired ceramic (LTCC) technology and experimentally verified. Series-fed array antennas integrated with scan angle enhancing meta lens (SAEMLs) confirmed the shift of the gain peak from 46° to 58°, proving that SAEML can effectively extend the scanning range of phased arrays with small gain variation.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Compact Shared-Aperture Dual-Band Dual-Circularly-Polarized Waveguide
           Antenna Array Operating at K/Ka-Band

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      Authors: Yilin Dong;Rong Xu;Yu-Hang Yang;Shi-Gang Zhou;
      Pages: 443 - 449
      Abstract: In this article, a compact shared-aperture dual-band dual-circularly polarized waveguide antenna array is presented to achieve high gain and wide bandwidth in full-duplex satellite communication at K/Ka-band. The designed antenna array can simultaneously operate at 20 GHz band with right-hand circular polarization (RHCP) radiation and 30 GHz band with left-hand circular polarization (LHCP) radiation. The array is composed of circular polarization (CP) waveguide antenna elements and full-corporate feed networks. The ridged spectrum polarizer is inserted in the square waveguide to form CP radiation in a stepped waveguide antenna element. The sequential rotation technique is adopted in feed networks to further improve CP axial ratio (AR) performance and bandwidth. The prototype of the proposed 4 $times4$ antenna array is fabricated and measured for demonstration. Experimental results show that the overlapped bandwidth in terms of reflection coefficients less than −10 dB and AR lower than 2 dB is 18–22 GHz for RHCP radiation in K-band, and the corresponding bandwidth for LHCP radiation in Ka-band is 28–32 GHz. The measured cross-polarization levels are better than 25.82 dB at 20 GHz and 20.25 dB at 30 GHz, and the measured peak gains at K/Ka-band are 23.94 and 26.87 dBic, respectively.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Robust Low Sidelobe Synthesis for Arbitrary Arrays Based on Gradient
           Ascent With Min-Oracle

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      Authors: Zhubin Shen;Jianfeng Li;Qihui Wu;
      Pages: 450 - 462
      Abstract: This article studies the robust pattern synthesis of a narrow main beam and low sidelobes of arbitrary arrays, which represents a classical but challenging problem for array antennas. In addition, pattern synthesis for a given sidelobe envelope is discussed. The synthesis problem is formulated as a nonconvex–nonconcave minimax problem with nonconvex constraints, which avoids the design of the optimal desired pattern and ensures the robustness of pattern synthesis for arbitrary arrays by nonconvex constraints. An algorithm named gradient ascent with min-oracle (GAmin) is proposed to address the considered minimax problem. Furthermore, the majorization–minimization algorithmic framework is used to reduce computational complexity. It is shown that for arbitrary linear and planar arrays, the proposed GAmin-based pattern synthesis method can perform well for pattern synthesis both without and with a given sidelobe envelope. A variety of numerical examples are provided to demonstrate the superior performance of the proposed method.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Dual-Band Shared-Aperture Variable Inclination Continuous Transverse Stub
           Antenna

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      Authors: Yunlong Lu;Yang You;Qingchun You;Yi Wang;Jifu Huang;
      Pages: 463 - 472
      Abstract: This article presents a dual-band shared-aperture variable inclination continuous transverse stub (VICTS) antenna with large beam coverage for both frequency bands. A novel hybrid radiating structure is introduced to enable approximately consistent initial beam direction at the boresight for both bands and therefore large beam coverage, by exciting different sets of the radiation elements at each of the two bands. The hybrid structure is formed of interlaced conventional CTS elements and those backed by double-ridge waveguide slots. The latter suppresses the lower band while allowing the high band to radiate. This configuration allows maximum aperture reuse. A parallel-plate waveguide (PPW) diplexer combines the generated plane waves from the two bands to enable one-side excitation. Combined with the nonuniform slow wave structure (SWS), optimized amplitude distribution is achieved across the two frequency bands, thereby improving the antenna efficiency. A prototype is designed, fabricated, and measured for 12.25–12.75 GHz (Ku-band) and 19.6–21.2 GHz (K-band). The measured reflection coefficients are kept less than −11.5 dB during the beam steering. At the center frequencies of 12.5 and 20.4 GHz, the measured beam coverage of over ±49° and ±59° in elevation plane is demonstrated from a relative rotation angle of 40°. During the beam steering, the measured peak gain varies in the range of 26.1–21.1 dBi/30.4–25.2 dBi at these two frequencies.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Low-Profile Ultra-Wideband and Wide-Scanning Phased Array for UHF
           Applications

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      Authors: De-Ming Sun;Zhang-Cheng Hao;Chen-Yu Ding;Rui-Jia Liu;Zi-Jun Guo;Hao-Yu Yin;
      Pages: 473 - 486
      Abstract: This article presents a novel low-profile ultra-wideband and wide-scanning array antenna using the transversely connected folded tightly coupled dipoles array (TCF-TCDA). The tightly coupled folded dipole arms are used to extend the operational frequency band with a simple feed structure. The capacitively-loaded metallic walls are adopted to move the problematic common-mode resonance out of the desired band and mitigate the bandwidth-limiting loop mode at the lower frequency, as well as reducing the weight and cost. A meta-surface-based wide angle impedance matching (MS-WAIM) layer is used to improve the beam scanning ability and lower the antenna profile, which consists of the star-shaped patches loaded on the dipole element. To demonstrate the wideband and wide scanning-range capability, a prototype is designed with an 8:1 bandwidth (0.41–3.3 GHz) at broadside, a scanning range of $pm mathrm{75}^{circ }$ from 0.5 to 3.25 GHz (6.5:1 bandwidth) in the E- and D-planes and $pm mathrm{50}^{circ }$ from 0.6 to 3.3 GHz (5.5:1 bandwidth) in the H-plane for active VSWR < 3.6. The proposed antenna has a very low profile, which is only $0.07lambda _{mathrm {low}}$ at the lowest operating frequency. A 16 $times $ 16 array prototype is fabricated and measured. Experimental results show that the design and measurement results have good agreement. The proposed antenna has an ultra-wide bandwidth, a wide scanning range, a very compact size and a low cost, which is a good candidate for modern wireless system.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Two-Dimensional Beam Steering Using a Stacked Modulated Geodesic Luneburg
           Lens Array Antenna for 5G and Beyond

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      Authors: Pilar Castillo-Tapia;Oskar Zetterstrom;Astrid Algaba-Brazález;Lars Manholm;Martin Johansson;Nelson J. G. Fonseca;Oscar Quevedo-Teruel;
      Pages: 487 - 496
      Abstract: Antennas for future communication systems are required to be highly directive and steerable to compensate for the high path loss in the millimeter-wave band. In this work, we propose a linear array of modulated geodesic Luneburg lens (the so-called water drop lens) antennas operating at 56–62 GHz. The lens array antenna features 2-D beam scanning with low structural complexity. The lenses are fully metallic and implemented in parallel plate waveguides (PPWs), meaning that they are highly efficient. Each lens is fed with 13 rectangular waveguides surrounded by glide-symmetric holes to suppress leakage. The lenses provide $mathrm{110}^{circ} $ beam coverage in the H-plane with scan losses below 1 dB. In order to scan in the E-plane, we use a feeding network based on a 1:4 power divider and three phase shifters. In this configuration, the array can scan $mathrm{60}^{circ} $ in the E-plane, albeit with higher scanning losses than in the H-plane. The lens array is manufactured and a good agreement between simulated and experimental results is obtained.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Support Vector Regression-Enabled Optimization Strategy of Dual
           Circularly-Polarized Shaped-Beam Reflectarray With Improved Cross-
           Polarization Performance

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      Authors: Daniel R. Prado;Parinaz Naseri;Jesús A. López-Fernández;Sean Victor Hum;Manuel Arrebola;
      Pages: 497 - 507
      Abstract: This work presents the optimization of a dual circular-polarized (CP) shaped-beam reflectarray with improved performance. To that end, the design methodology leverages surrogate models based on support vector regression (SVR) of the electromagnetic response of the constituent unit cell for a direct layout optimization of the antenna. The dual CP capability is achieved using a linear polarization (LP) Jerusalem cross integrated with an LP-to-CP polarization converter. A full description of the reflectarray analysis in CP is given. We also provide a missing demonstration in the literature of the fact that the direct coefficients in CP shape the copolar (CO) pattern of the corresponding polarization. This is applied to the optimization of a dual CP reflectarray with an isoflux pattern, achieving a reduction of more than 9 dB in the crosspolar (XP) pattern.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A UWB Low-Profile Hemispherical Array for Wide Angle Scanning

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      Authors: Carl Pfeiffer;Jeffrey Massman;
      Pages: 508 - 517
      Abstract: We report the first low-profile array on a doubly curved surface that supports wide angle electronic scanning and ultrawide bandwidth (7:1 ratio). The array elements are based on the balanced antipodal Vivaldi antenna (BAVA). The antennas are optimized for a good impedance match in an infinite planar array environment and are then deformed to fit along the surface of a hemisphere. The array is comprised of 104 linearly polarized BAVA elements arranged along a quadrilateral mesh on the surface of a 100 mm diameter hemisphere. The antennas and SMP connectors are 3-D printed out of titanium. The array has grating lobe-free operation at frequencies < 8 GHz. The array can also maintain relatively low sidelobe levels above 8 GHz compared with planar arrays because the aperiodicity of the hemispherical element locations reduces the magnitude of grating lobes. The simulated and measured realized gain is within 1 dB of the theoretical limit from 2.5–18 GHz and scan angles with $theta le {mathrm {90}}^{circ }$ except near 14 GHz where a resonance reduces the gain by 3 dB for some scan angles.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • High-Resolution Programmable Scattering for Wireless Coverage Enhancement:
           An Indoor Field Trial Campaign

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      Authors: James Rains;Jalil ur Rehman Kazim;Anvar Tukmanov;Tie Jun Cui;Lei Zhang;Qammer H. Abbasi;Muhammad Ali Imran;
      Pages: 518 - 530
      Abstract: This article presents a multibit reconfigurable intelligent surface (RIS) with a high phase resolution, capable of beam-steering in the azimuthal plane at sub-6 GHz. Field trials in realistic indoor deployments have been carried out, with coverage enhancement performance ascertained for three common wireless communication scenarios. Namely, serving users in an open lobby with mixed line-of-sight (LoS) and nonline-of-sight (NLoS) conditions, communication via a junction between long corridors, and a multifloor scenario with propagation via windows. This work explores the potential for RIS deployment to mitigate NLoS effects in indoor wireless communications. In a single transmitter (Tx), single receiver (Rx) NLoS link, received power improvement of as much as 40 dB is shown to be achievable by suitable placement of an RIS, with an instantaneous bandwidth of at least 100 MHz possible over a 3–4.5 GHz range. In addition, the effects of phase resolution on the optimal power reception for the multibit RIS have been experimentally verified, with a 2.65 dB improvement compared with a 1 bit case.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Design and Characterization of the Fully Metallic Gap Waveguide-Based
           Frequency Selective Radome for Millimeter Wave Fixed Beam Array Antenna

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      Authors: Wai Yan Yong;Abolfazl Hadaddi;Andrés Alayón Glazunov;
      Pages: 531 - 541
      Abstract: This article presents a bandpass frequency selective surface (FSS) radome based on fully metallic gap waveguide (GW) technology. The element of the proposed FSS radome consists of a conventional cross-dipole slot etched on metallic plates and positioned over a groove GW cavity. A design with a single GW-cavity layer was initially produced which was later optimized for performance, to comprise a dual GW-cavity layer, while considering both functionality and manufacturability. It is shown that the proposed FSS element offers a stable and wide bandpass (from 26 to 30 GHz) performance in the broadside direction for both transverse electric (TE) and transverse magnetic (TM) polarizations. For oblique angle of incidence, the suggested FSS element works up to 30° with a reduction in usable bandpass bandwidth performance to 26–28 GHz for both TE and TM polarizations. A $20 times 20$ -element GW-FSS array prototype has been fabricated and measured, which was integrated with a fixed-beam array antenna to further validate its functionality as a filtering radome. The findings show an excellent agreement between simulations and measurements. Hence, the proposed GW-FSS represents a great opportunity to develop an all-metallic FSS with low insertion loss, sharp-roll-off filtering, wideband performance, and inexpensive fabrication cost.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Broadband Millimeter-Wave Circularly Polarized Open-Ended Waveguide
           Antenna Using Stubs and Its Application in Forming an Array

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      Authors: Jing-Yi Zhang;Jin-Dong Zhang;Qiao-Yu Chen;Wen Wu;Da-Gang Fang;
      Pages: 542 - 549
      Abstract: A new broadband circularly polarized (CP) antenna using an open-ended waveguide is proposed in this article. By using two stubs at different positions of the open-ended waveguide, the amplitude and phase of the orthogonal fields are effectively adjusted. The method is applied to the millimeter-wave bands, and a single element as well as a four-element array are presented. Reasonable agreement between the measured and simulated results has been observed. The antenna element has a wide overlapping impedance bandwidth of 50% and a 3 dB axial ratio (AR) bandwidth of 50% covering 24–40 GHz, making it a promising candidate for wideband applications. The measured realized gains at 28 and 38 GHz are 6.7 and 6.9 dBic for an element and 12.3 and 13.9 dBic for an array, respectively.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Spherical Random Arrays With Application to Aerial Collaborative
           Beamforming

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      Authors: Athanasios G. Kanatas;
      Pages: 550 - 562
      Abstract: Spherical volumetric arrays with randomly distributed elements are studied using geometrical probability theory. The array elements are considered as points of an isotropic homogeneous binomial point process (BPP), randomly located within a 3-D ball. The presented results are based on the distance distribution of the $k$ th nearest element from the center of the ball. These elements are assumed to be the randomly distributed nodes of a wireless aerial network that cooperate to produce a beam toward a desired distant receiver. An alternative array elements’ distribution is also examined by placing a constraint to the distance of the farthest element and providing novel results on the average array factor, the average power pattern, and the directivity of the array. The half power beamwidth (HPBW), the peak sidelobe level (SLL), and the location of the peaks and nulls of the power pattern are examined in terms of the number of the array elements and the radius of the sphere. Finally, the impact of the location estimation errors on the performance of open-loop collaborative beamforming is examined both theoretically and using empirical simulation results.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Planar SIW-Based Mm-Wave Frequency-Scanning Slot Antenna Array With No
           Scan Blindness at Normal

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      Authors: Kirill Klionovski;Hanguang Liao;Sergey E. Bankov;Zubair Akhter;Atif Shamim;
      Pages: 563 - 569
      Abstract: Planar antenna reflectors are the modern design trend of both multibeam and frequency-scanning antenna arrays. The planar implementation of reflectors is typically performed using substrate-integrated waveguide (SIW) technology. A reflector’s profile can be different from the canonical one (parabolic, elliptic, hyperbolic, etc.) because of the effect of spatial dispersion of the reflection coefficient of the SIW-based surface. It should be synthesized considering the magnitude and argument of the field reflected from such a surface to maximize the efficiency of the reflection. In this article, we present a planar millimeter-wave (mm-wave) slot antenna array with SIW-based horn–reflector feeding. We analytically formulate the optimization of the SIW surface dimensions while accounting for the spatial dispersion of the reflection coefficient. We minimize the dimensions of the planar horn–reflector feeding. Finally, we demonstrate that using a dual-slot radiating element, and we can avoid the effects of scan blindness along the normal direction. A prototype has been built and a good agreement has been achieved between the measured results and the predicted results based on calculations. The prototype achieved ±17° beam scanning within 16% of the operational frequency range, with no scan blindness along the normal direction.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A 2D-Programmable and Scalable Reconfigurable Intelligent Surface Remotely
           Controlled via Digital Infrared Code

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      Authors: Andrey Sayanskiy;Andrei Belov;Ruslan Yafasov;Andrey Lyulyakin;Alexander Sherstobitov;Stanislav Glybovski;Vladimir Lyashev;
      Pages: 570 - 580
      Abstract: Reconfigurable intelligent surfaces (RISs) are promising and relatively low-cost tools for improving signal propagation in wireless communications. A RIS assists a base station (BS) in optimizing the channel and maximizing its capacity by dynamically manipulating the reflected field. Typically, RISs are based on dynamically reconfigurable reflectarrays (RAs), i.e., 2-D arrays of passive patch antennas, individually switchable between two or more reflection phases. The spatial resolution of provided reflected field patterns is governed by the aperture dimensions and the number of patches to meet the requirements of different communication scenarios and environments. Here, we demonstrate a 1 bit RIS for 5 GHz Wi-Fi band made by assembling together multiple independently operating and structurally detached building blocks all powered by the same DC source. Each block contains four separately phase-switchable patch antennas with varactor diodes and a common microcontroller extracting digital control commands from modulated infrared light illuminating the entire RIS. Such distributed light-sensitive controllers grant the possibility of scaling the aperture by adding or removing blocks without redesigning any control circuitry. Moreover, in the proposed RIS a full 2-D phase encoding capability is achieved along with a robust remote infrared control.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Reconfigurable Bidirectional Beam-Steering Aperture With Transmitarray,
           Reflectarray, and Transmit-Reflect-Array Modes Switching

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      Authors: Hang Yu;Pan Li;Jianxun Su;Zengrui Li;Shenheng Xu;Fan Yang;
      Pages: 581 - 595
      Abstract: The design and experiment of an electronically reconfigurable bidirectional spatially-fed array are presented, which combines the functionalities of reconfigurable transmitarray (TA), reflectarray (RA), and transmit-reflect array (TRA). First, we demonstrate a novel bidirectional unit cell composed of a tunable resonant layer between a pair of orthogonally oriented metal gratings. Two positive-intrinsic-negative (PIN) diodes are integrated into the tunable resonant layer to achieve the 1-bit phase resolution in either transmission or reflection mode. Based on the proposed unit cell, a 16 $times16$ -element array arranged in a square grid, which can be controlled independently by a field programmable gate array (FPGA)-based digital control circuit, is excited by a linearly-polarized horn to show the beam steering ability of reconfigurable TA and RA. To realize TRA function integration with the bidirectional beam independent steering simultaneously, the method based on superposition of the aperture fields (SAF) on the aperture is used. In SAF design, the entire aperture is divided into transmission and reflection modes co-existing, and the arrangement and phase distribution are optimized by particle swarm optimization (PSO) algorithm to achieve minimum sidelobe levels (SLLs) and peak gain of bidirectional beam. The measured results of the prototype demonstrate that the antenna can steer bidirectional beam both in simultaneous and time division operating modes, which is not reported to the best of the authors’ knowledge. Our proposed method opens a new avenue for the design of high-performance multifunctional reconfigurable antenna systems.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • High Aperture Efficiency Arced Conformal Array With Phasor Beam Steering
           Antenna

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      Authors: Ziheng Ding;Jingfeng Chen;Han Zhou;Xianling Liang;Ronghong Jin;
      Pages: 596 - 605
      Abstract: A phasor beam steering stacked patch antenna with abilities of both the amplitude and phase pattern reconfigurations is proposed and used for improving the aperture efficiency of arced conformal array. The phasor beam steering antenna is composed of two parasitic patches on the top integrated with four PIN diodes and a driven patch on the lower layer. By switching the bias states of the PIN diodes, the induced complex current of the top patch is alterable and the phasor beam steering can be delivered. Thus, in the conformal array design, the phase compensation can be realized by the phase pattern reconfiguration of the phasor beam steering antenna instead of the conventionally used phase delay lines. Meanwhile, the amplitude pattern reconfiguration of the phasor beam steering antenna can also be used for enhancing the contribution of side elements to the gain of axial beam. A four-element arced conformal array with the phasor beam steering antenna is designed and measured for verification. Both the simulated and measured results indicate that the realized gain of the proposed conformal array is 12.0 dBi, and the corresponding aperture efficiencies are improved up to 51.48%, which is better than the results of the arced conformal array with the phase compensation network.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Measuring Array Mutual Impedances Using Embedded Element Patterns

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      Authors: David Buck;Karl F. Warnick;Rob Maaskant;David B. Davidson;David F. Kelley;
      Pages: 606 - 611
      Abstract: The radiation pattern of an antenna element embedded in a multiport antenna such as a phased array depends on the loads connected to the array element ports. If the embedded element patterns (EEPs) are measured using at least two known loading conditions, the patterns can be used to determine the array mutual impedance matrix. In previous work, this result has been derived with the simplifying assumption that the impedance of the source connected to the driven element changes along with the load impedances connected to the nondriven elements. In a practical test configuration, the source impedance cannot be readily changed. We analyze the case of EEPs measured with a fixed source impedance and changing impedances on the nondriven elements. The transformation from one set of EEPs to another with fixed source impedance is more complex than in the case of a source impedance that changes with the load impedances. The transformation depends on the coupling between elements and is only weakly sensitive to the element self-impedances. With measured EEPs for an array of identical elements, the impedance matrix can be found up to a scale factor. We demonstrate the method experimentally by measuring the patterns of an antenna array terminated with one loading condition and repeating the pattern measurements with a different loading condition. The mutual impedance matrix extracted from the pattern measurements compared to network analyzer mutual impedance measurements is accurate to within 1– $2~Omega $ for most of the mutual impedances.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Conformal Frequency Selective Surfaces for Arbitrary Curvature

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      Authors: Cesar L. Valle;Gilbert T. Carranza;Raymond C. Rumpf;
      Pages: 612 - 620
      Abstract: An algorithm is introduced for generating frequency selective surfaces (FSSs) capable of conforming to any curvature while maintaining the proper size, shape, and spacing of the elements. Compared to traditional projection and mapping methods, the presented algorithm maintains the electromagnetic properties of the FSS array despite the curvature. The algorithm can be used to conform to radomes, parts of autonomous vehicles, or any surface. The algorithm is agnostic to both element design and surface curvature. This allows the user to design a FSS for any curved surface while maintaining its response comparable to a flat array. The algorithm outputs two standard tessellation language (STL) files, one describing the curved surface and the other the elements of the FSS placed onto the curved surface. This makes the algorithm suitable for 3-D printing using systems with more than three axes or for flexible electronics. Several examples of arbitrary surfaces are shown. Lastly, the algorithm was applied to a Jerusalem-cross (JC) FSS on a nonsymmetrical parabolic dome. The dimensions of the parabolic dome were chosen to test the response of the array on a rather extreme surface against a projected array on the same surface. Simulations were carried out using Ansys HFSS from the infinite array to finite arrays to confirm the operation. Three test surfaces were manufactured with measured results found to be in good agreement with the simulation.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Low-RCS Multifunctional Shared Aperture With Wideband Reconfigurable
           Reflectarray Antenna and Tunable Scattering Characteristic

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      Authors: Pan Li;Hang Yu;Jianxun Su;Liwei Song;Qingxin Guo;Zengrui Li;
      Pages: 621 - 630
      Abstract: This article presents a low radar cross section (RCS) single-layer multifunctional shared aperture (MSA) with tunable manipulation of radiation and bistatic scattering patterns over the same wide frequency band. A low-cost positive-intrinsic-negative (p-i-n) diode is used in the unit cell to evoke the $180^{circ } pm 20^{circ }$ reflection phase difference for $x$ -polarized incident waves; thus, the wideband beam steering and tunable bistatic scattering patterns can be generated. By integrating the interdigital capacitance (IC) into the unit cell, the reflection bandwidth limitation for $y$ -polarized waves at a higher frequency band is broken. Furthermore, the optimized multielement phase cancellation (OMEPC) method is adopted to maximize the RCS reduction (RCSR) bandwidth of $y$ -polarization. A 16 × 16-element MSA prototype is fabricated and measured. The experimental results show that the 3 dB gain bandwidth of the MSA is from 5.5 to 9.5 GHz with the fractional bandwidth (FBW) of 53.3%, and the common frequency band of 10 dB RCSR for $x$ - and $y$ -polarized waves is in the range of 4.5–9.6 GHz (FBW $=$ 72.3%). The low RCS MSA with tunable control of radiation and scattering patterns over a wide frequency band can be used in military radar and low detectable systems.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Liquid Sensor Based on Frequency Selective Surfaces

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      Authors: Peter M. Njogu;Benito Sanz-Izquierdo;Edward A. Parker;
      Pages: 631 - 638
      Abstract: A novel, simple and easy-to-fabricate liquid sensor using frequency-selective surfaces (FSSs) is proposed. The new sensor concept is based on modifying the capacitance between adjacent FSS elements when materials of different electrical characteristics are inserted. The change in capacitance produces a change in resonant frequency. The FSS design consists of a 9 $times $ 9 array of square loops on $0.31lambda times 0.31lambda $ square unit cells with trenches between the loops. The trenches are filled with liquids under test (LTUs). The structure operates at 4.6 GHz without any liquid. When liquids are inserted in the trenches, the resonance frequency varies in relation to the dielectric constant of the liquid. This is observed by measuring the transmission coefficient ( $S_{21}$ ). Butan-1-ol, ethanol, methanol, propan-2-ol, and xylene are used to demonstrate the sensing function. A maximum sensitivity of 8.65% for xylene was achieved. Furthermore, very low differences were observed between the measured and expected dielectric constant and loss tangent, thus validating the design. The device is inexpensive, compact, and easy to make and scalable for large-area operations in liquid detection for microwave sensing applications. This technique has potential applications in reconfigurable FSS.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Self-Progressive Near-Field Focusing 2-D Full Frequency Scanning Slot
           Array Antenna Based on Ridge-Gap Waveguide

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      Authors: Ya Fei Wu;Yongxin Guo;Yu Jian Cheng;
      Pages: 639 - 649
      Abstract: A millimeter-wave self-progressive near-field focusing (NFF) 2-D full frequency scanning ridge-gap waveguide slot array antenna is proposed in this article. In the proposed array antenna, the adjacent linear NFF leaky-wave antennas (LWAs) are connected end to end in a double layer folded structure to construct a self-progressive phase shift feed network. Thus, the desired high phase progression in the design of the 2-D frequency scanning is provided by the linear NFF LWAs themselves with the superposed propagation length. As a result, the NFF 2-D frequency scanning performance can be achieved without increasing antenna area based on the proposed high-density self-progressive feed network, which is built by applying the ridge-gap waveguide. The proposed antenna prototype is fabricated through the computer numerical control (CNC) machining process and is verified by the experiment. The test information of the object under test in the near-field region can be directly obtained with a certain frequency band, showing good promise in the near-field detection application.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Metagrating-Assisted High-Directivity Sparse Regular Antenna Arrays for
           Scanning Applications

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      Authors: Yaniv Kerzhner;Ariel Epstein;
      Pages: 650 - 659
      Abstract: We present an analytical scheme for designing metagrating (MG)-enhanced sparse antenna arrays. Unlike previous work, the proposed method does not involve time-consuming cost function optimizations, complex structural manipulations on the active array, or demanding computational capabilities. Instead, it merely requires the integration of a passive MG superstrate, a planar periodic arrangement of subwavelength capacitively loaded wires (meta-atoms), synthesized conveniently via a semianalytical procedure to guarantee suppression of grating lobes in the sparse configuration. Correspondingly, we extend previous formulations to enable excitation of the MG by the active array elements, deriving analytical relations connecting the passive and active element distribution and electrical properties with the scattered fields, eventually allowing resolution of the detailed device configuration leading to optimal directivity. Importantly, considering typical active array applications, the semianalytical synthesis scheme is further developed to take full advantage of the various degrees of freedom in the system, harnessing them to support scanning in a wide range of extreme angles while maintaining a single directive beam. The resultant methodology, verified in simulations to work well also for large finite arrays, offers an original path for mitigating grating lobes in sparse arrays with scanning capabilities, yielding a complete printed-circuit-board (PCB) compatible design without relying on full-wave optimization.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Fully Automated Design Method Based on Reinforcement Learning and
           Surrogate Modeling for Antenna Array Decoupling

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      Authors: Zhaohui Wei;Zhao Zhou;Peng Wang;Jian Ren;Yingzeng Yin;Gert Frølund Pedersen;Ming Shen;
      Pages: 660 - 671
      Abstract: Modern electromagnetic (EM) device design generally relies on extensive iterative optimizations by designers using simulation software (e.g., CST), which is a very time-consuming and tedious process. To relieve human engineers and boost productivity, we proposed a machine learning (ML) framework to solve the problem of automated design for EM tasks. The proposed approach combines advanced reinforcement learning (RL) algorithms and deep neural networks (DNNs) in an attempt to simulate the decision-making process of human designers to realize automation learning. Specifically, the RL-based agent can interact with the EM design software without engaging human designers, allowing for automated design. Besides, the data accumulated during EM software simulation in the early design stage are reused as training data to build a DNN surrogate model to replace the time-consuming EM simulation and further accelerate the training of RL to achieve better optimization of EM design. Two types of antenna array decoupling including $1times $ 2 and $1times $ 4 arrays working at 3.5 GHz are used as test vehicles to validate the proposed method. The decoupling metasurfaces designed by the proposed fully automated method based on RL showed satisfactory results comparable to the results achievable by human designers. This indicates that the proposed method can be used to build powerful tools to boost the design efficiency of EM devices.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • K-/Ka-Band Shared-Aperture Phased Array With Wide Bandwidth and Wide Beam
           Coverage for LEO Satellite Communication

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      Authors: Rui Sen Hao;Jin Fan Zhang;Shi Chao Jin;Dun Ge Liu;Ting Jun Li;Yu Jian Cheng;
      Pages: 672 - 680
      Abstract: A K-/Ka-band shared-aperture endfire phased array antenna is presented in this article. The antenna has the properties of dual wide bandwidths, orthogonal circular polarizations (CPs), wide beam coverage, and high isolation between the K-band and Ka-band channels. In this work, a new array topology is proposed to enhance the design freedom and the periodicity of the antenna array. Then, the filtering structures used to reflect the crossband coupled power also enhance the isolation between the K-band and Ka-band channels. The crossband mutual coupling is reflected and reradiated to generate the wideband CP beams. The high-order parallel plate waveguide (PPW) mode is suppressed to realize the wide CP beam coverage. The working bands at the boresight are 17.7–21.2 and 27.5–31.0 GHz, respectively. The polarizations are right-hand CP (RHCP) in K-band and left-hand CP (LHCP) in Ka-band. The maximal scan angles are ±60°. The axial ratios (ARs) are below 3 dB at boresight and below 5 dB when the beam scans to ±60°. The isolation between the K-band and Ka-band channels is higher than 40 dB.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Optimal Pattern Synthesis for Polarimetric Phased Array Antenna Using
           Representative Array Patterns

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      Authors: Jian Zhou;Chen Pang;Zhanling Wang;Yongzhen Li;Xuesong Wang;
      Pages: 681 - 696
      Abstract: To reduce pattern measurements and synthesis computations for an optimal array pattern, a set of full array patterns, named as representative array patterns (RAPs), is proposed, the number of which is smaller than that of the active element patterns (AEPs). Each RAP corresponds to one beam named as the representative beam. By optimizing the directions of these representative beams, the measured RAPs can be a good substitute for all AEPs. Compared with using the AEPs, the measurement cost and the computation time of the proposed method are proportionally cut. Considering the results of multiple evaluated directions, the optimal arrangement of representative beams is analyzed. Relative to using the AEPs, a highly consistent performance is achieved, of which the correlation coefficient of copolarization patterns can exceed 98%. For the simulated 10 $times 10$ array antenna, since merely 67 RAPs are utilized, a 33% reduction in pattern measurements and synthesis computations is obtained. This relative reduction ratio reaches 39% for the 16 $times 16$ array antenna and 50% for the 32 $times 32$ array antenna. The stability of the proposed method under multiplicative and additive pattern measurement errors is presented. Moreover, the proposed method is verified on a practical C-band 4 $times 4$ dual-polarized microstrip patch array antenna.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Remarks on Noise Shaping for Phased Array Analog Beamforming

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      Authors: Shahin Sheikh;Ahmed A. Kishk;
      Pages: 697 - 712
      Abstract: This article comprises three parts, which exhaustively investigates the noise-shaping approach in analog beamforming of phased array (PA) antenna. Specifically, the impact of digital filter design on different PA applications is studied. In the first part, an overview of noise shaping in a hexagonal lattice PA is investigated for the first time. Compared with the Nyquist square lattice, the hexagonal counterpart yields a much smaller invisible region which is a challenge for pushing the error out of the visible region. Nevertheless, it has been shown that the method suppresses the quantization lobes (QLs), realigns the point deviation, and may promote antenna gain. For those with critically large array pitch, the digital filter stopband may become prohibitively wide, contributing to a negligible antenna gain loss. The second part uses the method for restoring null(s). It is shown that the noise-shaping approach is quite effective in enhancing the fidelity of the system in nulling the spatially localized interferences. However, considering the discrepancy between addressing the QLs as a harmonic error and nulls buried beneath the quantization residue, the digital filter design is challenging and needs high attenuation level. Specifically, the number of nulls is an essential criterion for the method’s success. The computations are double-checked with full-wave simulations. The results verify the viability of the approach with a minor deflection from the computation. The third part investigates the noise-shaping approach in PA of the sparse element spacing. The complication of digital filter design with respect to antenna gain loss is investigated for different scenarios. Optimization is used for complicated cases to find an optimal filter to minimize the antenna gain loss.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Fast Computation of Resonant Metasurfaces in FDTD Scheme Using Dispersive
           Surface Susceptibility Model

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      Authors: Xiao Jia;Xiaoyi Wang;Yousef Vahabzadeh;
      Pages: 713 - 722
      Abstract: A new framework of scattering analysis of metasurfaces composed of an assemble of resonant scatterers, with a multistage analysis procedure, is presented. The metasurface analysis using this framework utilizes a dispersive surface susceptibility model (SSM) and a finite-difference time-domain (FDTD) method, replacing the traditional brute force simulation with the physics-based SSM. The SSM extraction for characterizing scatterers is provided, which then is used to replace detailed practical scatterers in numerical simulation. The SSM with the frequency-dependent features’ behavior is described by multiple-Lorentz pole pairs, and the coefficients of the Lorentz model are obtained by using a rational fitting method. An easy-to-implement FDTD algorithm combined with the Lorentz-described SSM is proposed and presented. The efficiency of the proposed framework is proven by comparing it with conventional FDTD. The validity of the proposed framework is verified using commercial EM simulation software. The use of this analysis procedure is demonstrated by two example scatterers. Through the examples, we discuss the requirement of the meshing lattice size, sensitivity of the algorithm to the incident angle, and influence of the edge effects on the bistatic radar cross section (RCS) computation.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Quad-Polarization Reconfigurable Fixed-Frequency Beam-Scanning
           Leaky-Wave Antenna Based on the Holographic Method for Millimeter-Wave
           Application

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      Authors: Shanzhe Wang;Zheng Li;Junhong Wang;
      Pages: 723 - 733
      Abstract: A quad-polarization reconfigurable fixed-frequency beam-scanning leaky-wave antenna (LWA) operating at millimeter-wave Ka-band is presented in this article. A low-loss groove gap waveguide (GGW) structure is employed for low-loss transmission and feeding, above which there locates a metal-covered superstrate. Two rows of inclined slots etched on the metal cover in a staggered arrangement operate as the radiated sources. A modified holographic method is presented, and the hologram can be manipulated by switching the states between “ON” and “OFF” of the p-i-n diodes, and hence the fixed-frequency beam-scanning property with polarization agility of four different polarization states can be realized, including horizontal polarization (HP), vertical polarization (VP), left-handed circular polarization (LHCP), and right-handed circular polarization (RHCP). Besides, measured results of the fabricated antenna are given to verify its performance. The measured peak gains at 30 GHz reach 11.3 dBi in the HP state, 13.0 dBi in the VP state, 11.5 dBic in the LHCP state, and 11.8 dBic in the RHCP state, respectively, with a beam-scanning range of 100° (from −50° to $mathrm{50}^{circ }$ ), showing good agreement with the simulated results.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Space-Time Electromagnetic Inverse Scattering Tomography of Objects With
           Affine Deformation

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      Authors: Nima Saliani;Ali Pourziad;Masoumeh Azghani;
      Pages: 734 - 743
      Abstract: In this article, an electromagnetic inverse scattering problem (EISP) method is implemented successfully to capture the dynamic phenomena of the scene with affine deformation. In the presented method, a new variational model has been suggested which is based on two error functions of the current and state equations. Moreover, two types of regularizers have been adopted in the proposed scheme. In the first type, two separated spatial total variation (TV) and smooth, temporal regularization terms are used. In the second kind, a TV regularization, being a function of both spatial and temporal variables, is used. It is shown that the second type gives better results compared to the first type. The minimization problem is solved by the first-order primal-dual optimization algorithm of Chambolle and Pock.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Ultra-Wide Band Polarization Converter Based on Ultra-Thin Bi-Layer Slot
           Structures

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      Authors: Jun-Ho Jeong;Jae-Yeong Lee;Jae-Hyung Jang;
      Pages: 744 - 751
      Abstract: An ultrathin linear-to-linear polarization converter exhibiting a high polarization conversion ratio (PCR) in an ultrawide bandwidth is fabricated on a printed circuit board (PCB). It is based on a bilayer slot structure that is electrically connected by via holes. Front- and back-sided slot structures are arranged in mutually orthogonal directions and function as receivers and radiators, respectively. The via holes provide a route for the transfer of electromagnetic energy received by the front-sided slot structures to the back-sided slot structures and radiate an electromagnetic wave having polarization orthogonal to that of the input electromagnetic wave. Moreover, two slots are employed for each unit cell design, and the locations of the via holes are carefully determined to achieve broadband polarization conversion. The via-hole positions that change the surface current distribution around the slot apertures enable the control of multiple resonance frequencies. Via holes are positioned to make first and second resonance frequencies that are blue-shifted toward the third resonance frequency, which broadens the operational band of the perfect polarization conversion. The 0.8 mm thick polarization converter exhibits PCR greater than 99% in the frequency band from 24.5 to 47 GHz.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Explicit Conversion Formulas Between Spherical Wave Expansions With Scalar
           and Vector Expansion Coefficients

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      Authors: Josef Knapp;Thomas F. Eibert;
      Pages: 752 - 762
      Abstract: Explicit formulas for converting spherical wave expansions with vector basis functions and scalar expansion coefficients into spherical wave expansions with scalar basis functions and vector expansion coefficients and vice versa are presented. The formulas are given in terms of Wigner-3- $j$ -symbols. The conversion formulas are derived by spherical harmonics expansions of products of two spherical harmonics and by levering on recurrence relations of the associated Legendre functions. The expansions with vector coefficients are redundant and explicit formulas are given for the linear combination of vector coefficients of which the expanded fields cancel identically to zero. The redundancy in the expansion can be used to find compact expansions with a minimum expansion order. For every vector spherical wave function, two expansions using scalar spherical harmonics are presented: on the one hand, a radial-component free expansion and on the other hand, a minimum-order expansion. The correctness of all expansions is verified with a simple computer code up to a mode order of 65. The agreement of the expanded near and far fields in both types of expansions is better than 14 digits of accuracy for most cases.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Extended Method of Lines to Model Cylindrical Graphene-Based Multilayer
           Structures

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      Authors: Ali Mehrdadian;Keyvan Forooraghi;Keyhan Hosseini;
      Pages: 763 - 773
      Abstract: In this article, the method of lines (MoL) is extended to analyze 2-D multilayer structures loaded with graphene plates in cylindrical coordinates. Accordingly, the admittance transformation matrices through a 2-D interface are derived taking into account the tensor-form conductivity of the magnetized graphene plate. The transformations determine the admittance matrices on all the planes of the multilayer structure. Furthermore, a technique to obtain the characteristic equation and hence the propagation constant of the structure is proposed by matching the fields at the interfaces loaded with graphene. As a result, the proposed method is able to analyze a generic graphene-loaded multilayer structure in cylindrical coordinates. As a proof of concept, the MoL is exploited to analyze 2-D cylindrical graphene microstrip and stripline transmission lines. The proposed method is validated by comparing the results with COMSOL simulations exhibiting a good agreement. Tuning the chemical potential of the graphene plate has potential applications in tunable microwave attenuators and phase shifters.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • High-Purity Multi-Mode Vortex Beam Generation With Full
           Complex-Amplitude-Controllable Metasurface

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      Authors: Quan Li;Chao Wu;Zhihui Zhang;Song Zhao;Bin Zhong;Song Li;Hongqiang Li;Lijun Jin;
      Pages: 774 - 782
      Abstract: Vortex beam with inherent orbital angular momentum (OAM) is promising in high-capacity communication. On multimode vortex beam generation, metasurface has shown exceptional advantages of integration and miniaturization. For the current widely used phase-only methods on multimode vortex beam generation by metasurface, the purity of the OAM-mode spectrum is severely affected. A new method for generation of multimode vortex beam with high mode purity is proposed in this article by reconstructing the complete complex amplitude information on the meta-device aperture. A 20 dB suppression of the crosstalk modes is experimentally observed for the co-directional multimode vortex beam generation, which is much improved compared to the traditional phase-only scheme. In addition, the proposed scheme also provides the capability of generating high-purity multimode vortex beams with arbitrary preset propagation directions and power allocations. This study provides a platform for high-performance vortex beam communication by increasing the signal-to-noise ratio and enabling the multicasting scenarios with customized capacity requirements.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Accurate and Efficient Method for Analyzing the Transfer Efficiency of
           Metasurface-Based Wireless Power Transfer System

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      Authors: Xiaonan Wu;Hao Xue;Shihao Zhao;Jiaqi Han;Mingyang Chang;Haixia Liu;Long Li;
      Pages: 783 - 795
      Abstract: An accurate and efficient calculation method for analyzing the transfer efficiency of a metasurface-based wireless power transfer system (ATEMWS-method) is proposed in this article. According to the amplitude and phase compensation information of the metasurface units (MUs) and using the superposition of the radiated electric field of each MU, the ATEMWS-method can calculate the wireless power transfer (WPT) efficiency from the metasurface to the energy harvester in any case. WPT systems based on a transmissive metasurface with a focused beam and a reflective metasurface with a high-gain directional beam are simulated to verify the method’s effectiveness and correction. The results show that the proposed method has high accuracy in evaluating the WPT efficiency and dramatically improves the near-field accuracy by more than 70% compared with traditional methods. To further verify the accuracy of the ATEMWS-method in the near-field region, WPT systems based on transmissive and reflective metasurfaces with focused beams are fabricated to compare the experimental measurement and calculation results. The calculated results of the proposed method are particularly close to both simulated and measured values with a relative error of less than 0.5%, while it takes only one-thousandth of the simulation time by the commercial software. Due to its accuracy and convenience, the proposed method provides guidance and simplifies the design difficulty for the metasurface-based WPT system.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Field Synthesis With Azimuthally Varying, Cascaded, Cylindrical
           Metasurfaces Using a Wave Matrix Approach

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      Authors: Chun-Wen Lin;Anthony Grbic;
      Pages: 796 - 808
      Abstract: In recent years, there has been extensive research on planar metasurfaces capable of arbitrarily controlling scattered fields. However, rigorous studies on conformal metasurfaces, such as those that are cylindrical, have been few in number likely due to their more complex geometry and corresponding analysis. Here, wave propagation in cascaded cylindrical structures consisting of layers of dielectric spacers and azimuthally varying metasurfaces (subwavelength patterned metallic claddings) is investigated. A wave matrix approach, which incorporates the advantages of both ABCD (transmission) matrices and scattering matrices ( $S$ matrices), is adopted. Wave matrices are used to model the higher-order coupling between metasurface layers, overcoming the fabrication difficulties associated with previous works. The proposed framework provides an efficient approach to synthesize the inhomogeneous sheet admittances that realize desired cylindrical field transformations. Design examples are reported to illustrate the power and potential applications of the proposed method in antenna design and stealth technology.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Complete Helmholtz Decomposition on Multiply Connected Subdivision
           Surfaces and Its Application to Integral Equations

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      Authors: A. M. A. Alsnayyan;Leo C. Kempel;B. Shanker;
      Pages: 809 - 817
      Abstract: The analysis of electromagnetic (EM) scattering in the isogeometric analysis (IGA) framework based on the Loop subdivision has long been restricted to simply connected geometries. The inability to analyze multiply connected objects is a glaring omission. In this article, we address this challenge. IGA provides seamless integration between the geometry and analysis using the same basis set to represent both. In particular, IGA methods using subdivision basis sets exploit the fact that the basis functions used for surface description are smooth (with continuous second derivatives) almost everywhere. On simply connected surfaces, this permits the definition of basis sets that are divergence-free and curl-free. What is missing from this suite is a basis set that is both divergence-free and curl-free, a necessary ingredient for a complete Helmholtz decomposition of currents on multiply connected structures. In this article, we achieve this missing ingredient numerically using random polynomial vector fields. We show that this basis set is analytically divergence-free and curl-free. Furthermore, we show that these bases recover curl-free, divergence-free, and both curl-free and divergence-free fields. Finally, we use this basis set to discretize a well-conditioned integral equation for analyzing perfectly conducting objects and demonstrate excellent agreement with other methods.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Neural Born Iterative Method for Solving Inverse Scattering Problems: 2D
           Cases

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      Authors: Tao Shan;Zhichao Lin;Xiaoqian Song;Maokun Li;Fan Yang;Shenheng Xu;
      Pages: 818 - 829
      Abstract: In this article, we propose the neural Born iterative method (NeuralBIM) for solving 2-D inverse scattering problems (ISPs) by drawing on the scheme of the physics-informed supervised residual learning (PhiSRL) to emulate the computing process of the traditional Born iterative method (TBIM). NeuralBIM uses independent convolutional neural networks (CNNs) to learn the alternate update rules of two different candidate solutions regarding the residuals. Two different schemes are presented in this article, including the supervised and unsupervised learning schemes. With the dataset generated by the method of moments (MoM), supervised NeuralBIM is trained with the knowledge of the total fields and contrasts. Unsupervised NeuralBIM is guided by the physics-embedded objective function founding on the governing equations of ISPs, which results in no requirement of the total fields and contrasts for training. Numerical and experimental results further validate the efficacy of NeuralBIM.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Characteristic Mode Decomposition Using the Scattering Dyadic in Arbitrary
           Full-Wave Solvers

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      Authors: Miloslav Capek;Johan Lundgren;Mats Gustafsson;Kurt Schab;Lukas Jelinek;
      Pages: 830 - 839
      Abstract: Characteristic modes are formulated using the scattering dyadic, which maps incident plane waves to scattered far-fields generated by an object of arbitrary material composition. Numerical construction of the scattering dyadic using arbitrary full-wave electromagnetic solvers is demonstrated in examples involving a variety of dielectric and magnetic materials. Wrapper functions for computing characteristic modes in method-of-moments, finite-difference time domain, and finite-element solvers are provided as Supplementary Material.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Synthesis of Clustered Concentric Ring Arrays Through Joint Optimization
           of Multi-Parameters

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      Authors: Jianhua Yang;Feng Yang;Peng Yang;Zhiyu Xing;
      Pages: 840 - 851
      Abstract: This article proposes a novel hybrid methodology that addresses the clustering of concentric ring arrays (CRAs) through joint optimization of ring radii, clusters partitions, and clusters excitations. It takes advantage of convex programming (CP) with respect to the excitation variables due to their convex nature. For the optimization of rings radii and clusters partitions, a subproblem is formulated by mix-integer programming with linear constraints, which is effectively resolved using the developed technique of mixed-integer linear-constraint genetic algorithm (MILCGA). A set of representative numerical experiments show the effectiveness of the proposed method and illustrate its potentialities, representing a promising solution for CRAs to obtain a suitable tradeoff between costs, robustness, flexibility, and beam control performances.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Self-Dual Integral Equation Based DDM for Scattering From Compound
           BoR-and-Non-BoR IBC Object

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      Authors: Marzieh Nasirian;Mojtaba Maddah-Ali;Mohsen Maddahali;Ahmad Bakhtafrouz;
      Pages: 852 - 858
      Abstract: A domain decomposition method (DDM) based on self-dual integral equation (SDIE) has been developed to analyze the scattering from a combinational structure with impedance boundary condition (IBC). From geometrical point of view, the combinational object is partially body of revolution (BoR) and is decomposed into BoR and non-BoR parts in the DDM framework. For the surface of all subdomains, which are modeled by IBC, the efficient SDIEs are used to construct the IE-based DDM. However, special care must be taken for the touching interfaces between subdomains. After choosing appropriate surface impedance for touching interfaces, the SDIEs of these surfaces are replaced by adapted self-dual Robin-type transmission conditions, which are derived by imposing field continuities in the SDIEs. Then, for transforming the IEs to a matrix system, the method of moments (MoM) is applied in an efficient manner to obtain an effectively reduced number of unknowns. Specifically, while the Rao-Wilton-Glisson (RWG) basis functions are used in non-BoR subdomains, the efficient BoR basis functions are utilized for expanding the currents of BoR subdomains. Memory requirements are considerably reduced in the proposed method, first by using the DDM, and second by utilizing the BoR basis in the BoR subdomain. Numerical results confirm the accuracy and efficiency of this approach.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Second-Order Nédélec Curl-Conforming Hexahedral Element for
           Computational Electromagnetics

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      Authors: Adrian Amor-Martin;Luis Emilio Garcia-Castillo;
      Pages: 859 - 868
      Abstract: We follow a systematic approach to obtain mixed-order curl-conforming basis functions for the hexahedron that are compatible with basis functions for tetrahedra and triangular prisms previously published. The approach is mathematically sound since we obtain the functions as the dual basis with respect to properly discretized Nédélec degrees of freedom. Well-conditioned bases without the need for added orthogonalization procedures are obtained. We provide simple closed-form expressions for second-order basis functions in a reference hexahedron in terms of integer coefficients and monomials. The expressions are ready to use as long as the appropriate geometric mappings are made. We apply the Method of Manufactured Solutions (MMS) to a finite-element double curl vector wave formulation for verification purposes; specifically, we conduct a study of the non-symmetrical structure of the corresponding tensor product finite-element space. We also solve generalized eigenvalue problems for well-known cavities. We provide the open-source code for generating the coefficients, evaluating the basis functions, and computing the finite-element matrices involved in some of the numerical solutions shown in the article.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Locally-Implicit Discontinuous Galerkin Time-Domain Method to Simulate
           Metasurfaces Using Generalized Sheet Transition Conditions

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      Authors: Liang Chen;Mehmet Burak Özakin;Ran Zhao;Hakan Bagci;
      Pages: 869 - 881
      Abstract: The generalized sheet transition conditions (GSTCs) are incorporated into a discontinuous Galerkin time-domain (DGTD) method to efficiently simulate metasurfaces. The numerical flux for GSTCs is derived for the first time using the Rankine–Hugoniot jump conditions. This numerical flux includes the time derivatives of fields, and therefore, explicit time integration schemes, which are traditionally used with DGTD, do not yield a stable time marching method. To alleviate this bottleneck, a new time marching scheme, which solves a local matrix system for the unknowns of the elements touching the same GSTC face, is developed. This locally implicit method maintains its high-parallel efficiency just like the traditional explicit DGTD schemes. Numerical results, which validate the accuracy of the proposed method against analytical solutions and demonstrate its applicability to the simulation of curved and space/time-varying metasurfaces, are presented.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Uncertainty EM Scattering Prediction for Inhomogeneous Dielectric Bodies
           of Revolution

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      Authors: Zi He;Shi-Xi Li;Da-Zhi Ding;
      Pages: 882 - 891
      Abstract: A perturbed volumetric integral equation is fabricated to predict the uncertain scattering characteristics for the in-homogeneous dielectric bodies of revolution (BoRs) targets. The transverse surface of the body of revolution is discretized in terms of the rectangular and triangular basis functions. In this way, all the unknowns are assigned to the electric flux density and the governing equation can be solved mode by mode. Both the geometrical and dielectric uncertainties are taken into consideration for EM scattering characteristics. On one hand, the geometrical shape uncertainty is described with the nonuniform rational B-spline surface by using several independent random variables. On the other hand, the dielectric uncertainty is represented by the perturbed permittivity. Thus, the volume integral equation is reconstructed by the perturbed electric flux density. Both the mean value and variance of the radar cross Section can be derived to account for the geometrical and dielectric uncertainties. Numerical results are given to show that the calculation efficiency of the proposed method is higher than that of the traditional Monte Carlo method.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Estimation and Separation of Ionospheric Narrow-Band Unknown O and X Waves

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      Authors: Wenqi Tang;Wenzhong Qu;Ling You;Tianyun Li;Jirong Xin;Songqiao Yang;
      Pages: 892 - 901
      Abstract: The geomagnetic field splits an electromagnetic wave into two characteristic waves, termed the ordinary (O) and extraordinary (X) waves. For the narrow-band unknown high-frequency (HF) signals, we develop a model for the oblique propagation of the characteristic waves. The two waves travel through similar paths in the ionosphere and incident on a small aperture array with the same direction of arrival (DOA) and perpendicular polarizations. In a short period, there is only amplitude ratio and phase difference between the two waveforms, resulting in an elliptically polarized resultant (R) wave. Based on the maximum likelihood estimation, DOA and elliptically polarized parameters of the R, O, and X waves are estimated using the antenna’s vector effective length and the geomagnetic field. The Cramér–Rao Bounds are also presented. In addition, the O and X waveforms are separated based on polarization differences. Simulation and experiment validate the model and performance of estimators. DOA estimator for the R wave outperforms the estimator for the characteristic waves and the estimator for matching the energy of orthogonal polarizations. One of the separated characteristic waves presents smoother and shallower fading than the R wave.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Dyadic Green’s Function of Perfect Electromagnetic Conductor Rectangular
           Waveguides and Cavities

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      Authors: Seyyed Abbas Sahafi;Mohsen Ghaffari-Miab;
      Pages: 902 - 909
      Abstract: In this article, we present the dyadic Green’s functions (DGFs) for electric dipole excitation of perfect electromagnetic conductor (PEMC) rectangular waveguides and cavities. To derive the DGFs of a PEMC rectangular waveguide, we define two sets of orthogonal vector wave functions, that satisfy the boundary conditions at the waveguide walls. The theory of finding the DGF of this waveguide is based on the Ohm-Rayleigh method and orthogonal properties of the rectangular vector wave functions. By having the DGFs of this waveguide, one can derive the DGFs of a PEMC rectangular cavity using the scattering superposition (SSP) principle. The derived electric DGF of this waveguide is used to obtain the electric field propagated inside the waveguide due to an arbitrary current distribution. The distribution of the electric field inside the PEC, PMC, and PEMC waveguides will be obtained and compared with each other.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Numerically Efficient Method for Predicting the Scattering
           Characteristics of Complex Moving Targets

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      Authors: Dihia Sidi Ahmed;Paola Russo;Graziano Cerri;Laetitia Thirion Lefèvre;Régis Guinvarc’h;Giovanni Manfredi;
      Pages: 910 - 920
      Abstract: This article presents a new computational approach that allows rapid analysis of the electro-magnetic scattering (EMS) characteristics of static or moving complex radar targets. The scattering features of the object are represented through a generalized scattering matrix H, whose elements can be measured or computed using conventional numerical techniques, for example, CST software in the proposed case, and considering prescribed sampled directions. A cardinal series then is adopted to reconstruct the complete scattering pattern by suitably extending the approach to calculate the target’s scattering matrix for any incidence wave and any observation point. The number of finite samples, that is, the dimension of the scattering matrix depends only on the maximum dimension of the target. A PEC sphere and a PEC 3-D complex object have been analyzed in detail. Precise, fast, and stable sampling algorithms have been applied to these targets in the static case and in motion. In particular, the field scattered by the moving objects is then used to carry out the micro-Doppler analysis of the object radar signature.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Spatial Non-Stationary Near-Field Channel Modeling and Validation for
           Massive MIMO Systems

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      Authors: Zhiqiang Yuan;Jianhua Zhang;Yilin Ji;Gert Frølund Pedersen;Wei Fan;
      Pages: 921 - 933
      Abstract: Massive MIMO is envisioned as a promising technology in 5G and beyond 5G communication. Channel models are of great importance for the development and performance assessment of massive MIMO systems. Since massive MIMO systems are equipped with large-aperture antenna arrays, antenna elements at different spatial positions would observe different channel multipath characteristics, which is so-called spatial nonstationarity (SnS). The SnS property of multipaths has been observed in many reported massive MIMO channel measurements. However, characterization and explanations of SnS have not been adequate in existing statistical channel modeling, and deterministic models (e.g., ray tracing) are difficult to implement due to the high complexity. This article proposes a realistic yet low-complexity SnS channel modeling framework for massive MIMO systems and its validation based on both channel measurements and ray-tracing simulations. In this work, we first perform a 6 GHz-bandwidth millimeter-wave (mmWave) indoor channel measurement campaign with a 0.5 m radius virtual uniform circular array (UCA), where the SnS phenomena are clearly observed. Then, we propose the massive MIMO channel modeling framework that captures the observed SnS property from the physical propagation mechanisms of dominant multipaths in mmWave channels, i.e., blockage, reflection, and diffraction. Compared to traditional stationary channel modeling, only one extra parameter accounting for SnS has been added in the proposed framework, which is desirable for its low-complexity implementation. Finally, the proposed framework is validated with site-specific ray-tracing simulations. The SnS phenomena observed in the measurements are reproduced well in the modeling results according to the proposed framework, and high similarities between the target channels and modeling results are achieved. The proposed framework is valuable for the development of massive MIMO systems since it is realistic, low complexity- and accurate.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • On the Application of Orthogonality Sampling Method for Object Detection
           in Microwave Imaging

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      Authors: Won-Kwang Park;
      Pages: 934 - 946
      Abstract: We consider a further development of the orthogonality sampling method (OSM) for a fast localization of small object in microwave imaging (MI). In contrast to the scenarios considered in traditional approaches, if the location of the transmitter and the receiver is the same, it is very hard to measure the scattering parameter data or to distinguish the weak scattered signal from the relatively high antenna reflection. Here, we set the unknown measurement data as a constant and design an indicator function for the OSM. To demonstrate the applicability of the OSM and its dependence on the constant, we show that the designed indicator function can be represented in terms of an infinite series of the Bessel functions of integer order, antenna configuration, and applied constant. To improve the imaging performance for a proper identification of the object, we design a new indicator function of the OSM with multiple sources, rigorously explore its mathematical structure, and discover some properties including the improvement and uniqueness. Simulation results with synthetic and real data are exhibited to support the theoretical results and to illustrate the pros and cons of the designed OSM.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Unrolled Convolutional Neural Network for Full-Wave Inverse Scattering

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      Authors: Yarui Zhang;Marc Lambert;Aurélia Fraysse;Dominique Lesselier;
      Pages: 947 - 956
      Abstract: An unrolled deep learning scheme for solving full-wave nonlinear inverse scattering problems (ISPs) is proposed. Inspired by the so- called unrolled method, an iterative neural network structure combining the contrast source inversion (CSI) method and residual network (ResNet) is designed. By embedding the CSI iterations into the deep learning model, the domain knowledge is well incorporated into the learning process. Thorough numerical tests are carried out to evaluate the performance, stability, robustness, and reliability of the proposed approach. Comparisons with the widely used U-net structure and CSI exhibit the advantage of the proposed approach.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • ISAR Imaging for a Composite Target-Layered Rough Surface Scene Based on
           the Accelerated Time-Domain Scattering Algorithm

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      Authors: Rui Wang;Lei Liao;Guangbin Guo;Lixin Guo;
      Pages: 957 - 969
      Abstract: Most existing imaging studies are mainly used for a single target or a composite scene consisting of a target and a rough surface (TRS) below it, such as the target-ocean scene. This article focuses on inverse synthetic aperture radar (ISAR) imaging of a special composite scene consisting of a target and layered rough surfaces (TLRS) below it, such as a target and a snow-soil layered scene. Differently from previous imaging algorithms based on the frequency-domain (FD) method, this article combines the time-domain ray bouncing (TDRB) method with imaging algorithms to develop an accurate ISAR imaging framework to obtain composite images of the TLRS scene. To improve the simulation efficiency of the time-domain (TD) echo matrix for ISAR imaging, the multi-thread parallel is used to accelerate the TD scattering algorithm, then, the ISAR imaging formulas based on scattering field expressions in the TLRS scene are derived. Since the linear frequency modulation pulse used in traditional radar imaging has longer pulsewidth than the Gaussian, the matched filter is modified to realize pulse compression under modulating Gaussian pulse excitations to enhance the imaging efficiency. Simulation results show that the proposed ISAR imaging framework ensures the image quality and improves the simulation efficiency significantly. Finally, the ISAR images of the target-snow-soil scene with different parameters are simulated. This article addresses the correlation between the scattering mechanism and image features for ISAR images based on different scattering components, a topic that the literatures do lack.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Fast Antenna Characterization With Numerical Expansion Functions Built
           With Partial Knowledge of the Antenna and Accelerated Asymptotic Methods

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      Authors: Marco Righero;Giorgio Giordanengo;Lorenzo Ciorba;Giuseppe Vecchi;
      Pages: 970 - 983
      Abstract: We describe a method to use numerical simulations concurrently with measurements (near-field data) to characterize the radiation properties of an antenna (far-field) with a strongly reduced number of samples. Both the simulations and experimental data are dealt with as sources of information toward obtaining the desired characterization. Simulations compensate for data scarceness, allowing to obtain an accurate characterization with fewer data than with measurements only, and the few measured data allow the comprehensive numerical proxy to get tuned to the true antenna under test (AUT). The method uses partial knowledge of the antenna and leverages accelerated asymptotic numerical methods to perform the numerical simulations needed by the algorithm. We report experimental tests of performance, both in terms of accuracy and speed-up with respect to the classical methods, with reflector antennas up to 27 wavelength. It is important to note that good results are obtained both when samples are taken on irregular optimized grids and on regular grids usually resulting from the conventional measurement rigs.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Path Loss and Shadowing Modeling for Vehicle-to-Vehicle Communications in
           Terrestrial TV Band

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      Authors: Pawel Kryszkiewicz;Paweł Sroka;Michal Sybis;Adrian Kliks;
      Pages: 984 - 998
      Abstract: Vehicle platooning is considered as one of the key use cases for vehicle-to-vehicle (V2V) communications. However, its benefits can be realized only with highly reliable wireless transmission. As the 5.9 GHz frequency band used for V2V suffers from high congestion, in this article, we consider the use of the terrestrial TV frequencies for intra-platoon communications. In order to be able to evaluate the potential of the new bands fully, propagation models for V2V communications at such frequencies are needed. Therefore, this article reports new V2V propagation measurements and their modeling results. In particular, we propose a double slope double shadowing model as the most accurate one, based on a comparison of various models using the Bayesian information criteria. We also investigate the space–time autocorrelation properties of shadowing, which turned out to be dependent on the speed of vehicles. The proposed path loss and shadowing model differs from the ones proposed for the 5.9 GHz band; mostly, in favor of the TV band, as shown by, e.g., no statistically significant impact of a blocking car.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Wideband Low-Profile Connected Rectangular Ring Dielectric Resonator
           Antenna Array for Millimeter-Wave Applications

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      Authors: Yan-Ting Liu;Boyuan Ma;Shaode Huang;Shiyan Wang;Zhang Ju Hou;Wen Wu;
      Pages: 999 - 1004
      Abstract: A wideband low-profile connected rectangular ring dielectric resonator (DR) antenna (DRA) array is presented for millimeter-wave (mmWave) applications. It consists of four rectangular ring DRA elements. The DRA elements are excited by microstrip feedlines through four slots on the ground plane. A slot mode, the DRA ${mathrm {TE}}^{text {y}}_{1delta 1}$ mode, and the perturbed ${mathrm {TE}}^{text {y}}_{3delta 1}$ mode are simultaneously excited, giving a wideband design. To avoid the alignment problem, the DRAs are connected to their adjacent elements through dielectric arms. It is found that the position of the dielectric arms has significant effects on the antenna performance. To demonstrate the idea, a prototype with a dielectric constant of 20.8 was designed, fabricated, and tested for licensed mmWave bands (24.25–29.5 GHz). A reasonable agreement between the measured and simulated results is observed. The measured 10 dB impedance bandwidth ( $vert text{S}_{11}vert le - 10$ dB) is 31.6% (22.52–30.97 GHz), with a measured boresight realized gain being higher than 8 dBi from 22.5 to 30 GHz. The measured mutual couplings between the DRA elements of the array are lower than −20 dB in the operating frequency range. Furthermore, our prototype has a low profile of $0.074~lambda _{0}$ , where $lambda _{0}$ is the wavelength in air at the center frequency.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Communication Compact Dual-Band Hybrid Dielectric Resonator Antenna for 5G
           Millimeter-Wave Applications

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      Authors: Lun-Xue Cui;Xin-Hao Ding;Wen-Wen Yang;Lei Guo;Li-Heng Zhou;Jian-Xin Chen;
      Pages: 1005 - 1010
      Abstract: In this communication, a new kind of dual-band hybrid dielectric resonator antenna (DRA) with its array design and extended dual-polarized version is presented for fifth generation (5G) millimeter-wave (mm-Wave) applications. The hybrid antenna that integrates three types of resonators of strip, slot, and DRA can generate four resonances in 28 and 39 GHz frequency bands. In this design, the strip and slot modes are used to cover the lower frequency band of 26.41–30.42 GHz, while the TE111 and TE131 modes of the DRA are employed to cover the upper frequency band of 36.05–40.88 GHz. It shows that the 5G mm-Wave bands of n257 and n260 can be covered simultaneously. It should be mentioned that our proposed hybrid antenna has a compact size of $0.34lambda _{01} times 0.36lambda _{01} times 0.1lambda _{01}$ ( $lambda _{01}$ means the free-space wavelength at 28 GHz). Based on the compact size of the antenna element, a $1 times $ 5 antenna array with the capability of beam steering is designed and simulated. Wide steering angles of ±50° and ±40° can be obtained at 28 and 39 GHz frequency bands, respectively. Furthermore, an extended dual-polarized antenna configuration is also described and measured that provides similar two-port impedance and radiation performance with the single-port counterpart.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Pattern Reconfigurable Yagi Antenna Based on Active Corrugated Stripline

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      Authors: Jiayuan Lu;Hao Chi Zhang;Pei Hang He;Meng Wang;Tie Jun Cui;
      Pages: 1011 - 1016
      Abstract: We present a method of designing pattern reconfigurable Yagi antenna based on the active corrugated strip line (ACSL) technology. A conventional dipole is used as a driven element, and a pair of ACSLs in different states is set on both sides of the dipole symmetrically. The ACSLs in different states have different average phase constants ( $beta _{mathrm {ave}}$ ), where the ACSL with a lower $beta _{mathrm {ave}}$ serves as a director, while the other serves as a reflector. By changing the $beta _{mathrm {ave}}$ of the ACSLs, a front-to-back pattern reconfigurable Yagi antenna is realized. A prototype of the proposed antenna working at the center frequency of 2.4 GHz was fabricated and measured to validate the predicted performance. The fabricated antenna has a compact size ( $0.42lambda _{0}times 0.42lambda _{0}$ , $lambda _{0}$ is the wavelength in space) and low profile ( $0.004lambda _{0}$ ). The measured −10 dB impedance bandwidth and the gain of the antenna are 8.3% and 6.2 dBi (at 2.4 GHz), respectively.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Novel Metamaterial Lined Probe for High Precision Planar Near-Field
           Measurements

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      Authors: Lucille Kuhler;Andrea Giacomini;Nathalie Raveu;Gwenn Le Fur;Luc Duchesne;
      Pages: 1017 - 1022
      Abstract: For planar near field (PNF) antenna measurements, the size of the probe is a critical parameter since the multiple reflections with the device under test (DUT) affect the overall measurement uncertainty. In this communication, the modal expansion theory (MET) is used to design an open-ended waveguide (OEW) with reduced cross section, using a metamaterial lining of the inner walls of the probe. The performance of this novel design is compared in a measurement experiment to a standard metallic probe covering the same nominal bandwidth.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Holey SIW Horn Antenna Based on an H-Plane Lenswise Wavefront Collimation

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      Authors: Andrés Biedma-Pérez;Pablo Padilla;Cleofás Segura-Gómez;Ángel Palomares-Caballero;
      Pages: 1023 - 1028
      Abstract: This communication presents an H-plane substrate integrated waveguide (SIW) horn antenna whose directivity is enhanced using holey unit cells along the horn flaring. By wisely drilling the horn antenna, it is possible to reduce the phase error in the aperture which is a common problem in horn antennas if the optimum dimensions are not used. An analysis of the distribution of the unit cells along the horn antenna has been carried out to achieve the desired equivalent refractive indices. By changing the hole radius, different equivalent refractive indices can be tuned with a wideband performance. This fact enables the implementation of a collimation zone inside the horn antenna which transforms the pseudocircular wavefront into a quasi-planar one in the radiating aperture. The produced directivity is similar to the horn antenna with the optimum dimensions, but a longitudinal reduction of 53.7% and a higher realized gain are achieved. A holey SIW horn antenna is designed and manufactured. The measured results show an impedance bandwidth performance below −10 dB from 34.3 to 44.5 GHz (25.9%) with a realized gain above 10 dBi. The gain difference regarding an SIW horn antenna without the collimation zone is about 2–3 dBi in the operating frequency range.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Additively Manufactured Dual Circularly Polarized Antennas With
           Bidirectional Same-Sense Radiation and Wide Bandwidth Characteristics

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      Authors: Zi Long Ma;Xin Feng Xiao;
      Pages: 1029 - 1034
      Abstract: This communication presents two additively manufactured bidirectional circularly polarized (CP) antennas. Each antenna radiates the same-sense CP waves in opposite directions and has the capability of altering the CP state to either right-hand CP (RHCP) or left-hand CP (LHCP) by switching the feeding ports. They adopt the same scheme of combining a linearly polarized (LP) bidirectional source and two polarizers of the same type. Different polarizers, a single-slab dielectric polarizer (Ant 1) and a linearly tapered slot polarizer (Ant 2), are proposed and applied for them, respectively. The LP source adopts a circular waveguide-based structure. By altering the orthogonal degenerate modes in the waveguide, the CP states can be switched correspondingly. To validate the design ideas, prototypes of the two antennas are fabricated and tested. Experimental results show that the axial ratio bandwidth (ARBW) of Ant 1 and Ant 2 is 30.3% (4.9–6.66 GHz) and 17.9% (5.26–6.3 GHz), respectively. Within the ARBW, their gain is 8.4± 0.8 and 7.2± 1 dBic, respectively. These results demonstrate that both antennas exhibit the advantages of wide band, high gain, and ease of fabrication over the conventional designs.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Novel Programmable Stacked Patch Antenna With the Diversity of Sixteen
           Linear Polarizations and Four Frequency Bands

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      Authors: Pan Guo;Wenjie Zhong;Shu-Lin Chen;Dingzhao Chen;Yanhui Liu;
      Pages: 1035 - 1040
      Abstract: A highly multifunctional antenna with multilinear polarizations (MLPs) and multibands (MBs) is proposed, which can operate over four reconfigurable frequency bands, each band having 16 switchable linear polarizations (LPs) at an 11.25° interval. The larger number of MLPs is achieved by developing an odd–even switching strategy for the independently controlled p-i-n diodes placed between the inner patch and outer sector patches. The diode control is enabled by a field programmable gate array (FPGA) with an engineered biasing network. Moreover, the reported antenna can switch among four continuous bands for each LP, covering a combined range larger than 35%. It is an attractive feature, yet a challenging task for an antenna with such a large number of MLPs. This is realized by utilizing a double-layer feeding strategy with appropriate sector-patch activation, which is particularly appealed to such a highly multifunctional antenna. Furthermore, the antenna has a rotational symmetry along the azimuthal direction and, hence, all the LPs show almost rotationally invariant pattern shapes and gains. The measured results are consistent with the simulated ones, commonly validating the effectiveness of our design.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Wideband High-Gain Circularly Polarized Substrate Integrated Cavity
           Antenna Array for Millimeter-Wave Applications

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      Authors: Xiao-Chuan Wang;Yi-Jie Xia;Jia-Hui Yang;Wen-Zhong Lu;
      Pages: 1041 - 1046
      Abstract: A wideband high-gain circularly polarized (CP) substrate integrated cavity (SIC) antenna array is presented for millimeter-wave applications. The proposed antenna element is simply composed of a slot-coupled high-order-mode resonant square SIC and a pair of obliquely placed strip-shaped parasitic patches on the top surface of the SIC. The parasitic patches are used to adjust the aperture electromagnetic field distribution and phase of the two orthogonal resonant modes of TM211 and TM121 in the SIC to achieve a high-gain CP radiation and meanwhile introduce an additional cavity-backed slot-dipole CP radiation to extend axial ratio (AR) bandwidth of the proposed antenna element. By combining the above two high-gain CP radiation mechanisms, a wideband high-gain CP SIC antenna element is achieved. The simulated results of the proposed antenna element show an overlaid bandwidth of 20.36% from 26.20 to 32.14 GHz, while considering the −10 dB reflection coefficient, 3 dB AR, 3 dB gain bandwidths properties, and a maximum right-hand CP gain of 10.53 dBi at 29.40 GHz. On this basis, a wideband high-gain 8 $times $ 8 CP array fed by a full-corporate substrate integrated waveguide (SIW) network is designed and fabricated. The measured results show that the proposed array has an overlaid bandwidth of 21.72% from 25.85 to 32.15 GHz and a measured gain of up to 26.10 dBic at 29.00 GHz.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Synthesis of Continuous Source Current for Gain Enhancement and Sidelobe
           Suppression of High-Order Mode Dipoles

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      Authors: Yu Luo;Ni Zhang;Zhi Ning Chen;Wenxing An;Kaixue Ma;
      Pages: 1047 - 1052
      Abstract: A synthesis method of continuous source current on a high-order mode dipole is proposed to enhance gain and suppress sidelobe levels (SLLs) based on compression coefficients. First, a high-order mode dipole with the current distribution determined by designed compression coefficients is proposed to generate a typical continuous source. Then, a pattern synthesis method of continuous source current is presented to enhance gain with desired SLLs by calculating the compression coefficients. Finally, the fifth-order mode dipole is designed to verify the proposed synthesis method. Both measurement and theoretical prediction show the gain of 6.6 dBi and an SLL of −13.3 dB by the single dipole of the length of 1.5 wavelengths at 3.25 GHz. Compared with an array composed of three convention half-wave dipoles, the proposed fifth-order mode dipole of a similar length achieves a gain increase up to 1.13 dBi, or an effective length increases up to 30% while the SLL keeps unchanged.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Design of Self-Decoupling Dielectric Resonator Antenna With Shared
           Radiator

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      Authors: Yu-Zhong Liang;Fu-Chang Chen;Wen-Feng Zeng;Qing-Xin Chu;
      Pages: 1053 - 1058
      Abstract: The method of mode cancellation to design a two-port dielectric resonator antenna (DRA) for an in-band full-duplex (IBFD) application is investigated in this communication. The whole antenna structure is straightforward, only composed of a single DRA element, a pair of feeding lines, and a pair of metallic probes. Attributing to the features of different modes used in this design, mutual coupling between the exciting port and the passive port can be suppressed to an extremely low level without using an extra decoupling structure. A prototype is fabricated and measured for verification. The measured results demonstrate that the proposed antenna has broad bandwidth and high isolation level can be achieved throughout the whole working band.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • 3D Printed Directive Beam-Steering Antenna Based on Gradient Index Flat
           Lens With an Integrated Polarizer for Dual Circular Polarization at W-Band
           

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      Authors: J. Melendro-Jimenez;P. Sanchez-Olivares;A. Tamayo-Dominguez;X. Sun;J. M. Fernandez-Gonzalez;
      Pages: 1059 - 1064
      Abstract: In this communication, the design of a circularly polarized (CP) perforated gradient index (GRIN) flat lens antenna with directive beam-steering properties is presented for millimeter-wave applications at W-band (75–95 GHz). The dielectric lens, fed by an open-ended square waveguide (SWG) located in the lens focal plane, enhances the radiation in a particular direction, generating a high-directivity beam with planar wavefront. The integration of a dielectric polarizer with the lens allows the conversion from a linearly polarized (LP) incident wave to a CP-emitted wave over the whole bandwidth. Horizontally and vertically polarized waves, achieved by the excitation of the fundamental SWG TE01 and TE10 modes are transformed into left-hand CP and right-hand CP waves, respectively. A ±30° scan range in both azimuth and elevation planes is demonstrated for the whole frequency range, attained by displacing the feed along the focal plane of the lens. Lens and polarizer are manufactured as a single piece by stereolithography (SLA) 3-D printing technology with Form 3 Formlabs 3-D-printer. Measured results show maximum measured directivity values that range from 23.5 to 23.8 dB, a remarkable circular polarization purity as a wide axial ratio bandwidth of 20.58% (< 3 dB), from 77.5 to 95 GHz, is achieved for the principal beam steers and an aperture efficiency for broadside beam direction between 90.32% and 57.34% in the frequency band of interest.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Compact Dual-Polarized Filtering Antenna Based on Differential Feeding and
           Double-Layer Metasurface

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      Authors: Bing-Jie Chen;Xue-Song Yang;
      Pages: 1065 - 1070
      Abstract: A compact dual-polarized filtering antenna with differential feeding and double-layer metasurface is investigated. The proposed filtering antenna consists of a pair of suspended crossed dipoles, a double-layer metasurface, eight off-center metalized vias, and four center-shorted square split rings (CS-SSRs). By utilizing the double-layer metasurface and the off-center metalized vias, a radiation null is realized in the upper and lower stopbands, respectively. Besides, two more radiation nulls are obtained at the two band edges by loading CS-SSRs beside the crossed dipoles, which further suppresses the radiation level in the stopbands and improves the frequency selectivity. The performance of the proposed filtering antenna is verified by both simulation and measurement. It exhibits a 20.7% (4.31–5.32 GHz) measured impedance bandwidth with a compact aperture size of $0.56lambda _{0} times 0.56lambda _{0}$ . ( $lambda _{0}$ is the free-space wavelength at 4.8 GHz.) The measured in-band average gain achieves 6 dBi with suppression levels in the lower and the upper out-of-bands reaching 18.4 and 21.5 dB, respectively.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Expedited Amplitude and Phase Tolerance Analysis of Reflector Antenna
           Systems With Vector Spherical Waves

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      Authors: Pedro Robustillo;Juan Córcoles;Jesús Rubio;
      Pages: 1071 - 1074
      Abstract: This work presents the relevant advantages of analyzing a complete reflector antenna system based on: 1) the expansion of the feed radiated field in terms of vector spherical waves (VSWs) and 2) the characterization of the reflector domain with VSWs. It requires that the reflector be initially analyzed under the illumination of each single VSW. The output of each of these analyses is the radiated field of the reflector for each VSW excitation. Then, the accurate response of the complete antenna system, both in amplitude and phase, can be directly obtained by just linear combination of these individual-VSW-excited radiated fields, weighted by the feed transmission vector that relates the coefficients of the VSW expansions for the feeder with its input excitation mode. Thanks to the orthogonality of the VSWs, and the applicability of the far-field approximation, it turns into a very efficient approach for the whole end-to-end analysis, adding useful capabilities and flexibility for the expedited assessment of tolerances.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Compact Dual-Band High-Efficiency Antennas Based on Spoof Surface Plasmon
           Polaritons

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      Authors: Dou Tian;Amin Kianinejad;Ting Shi;Chen Guo;Jiafu Wang;Anxue Zhang;
      Pages: 1075 - 1080
      Abstract: A compact dual-band high-efficiency antenna based on spoof surface plasmon polaritons (SSPPs) is proposed by well exciting both the TM10 mode and the LC resonant mode. Each mode can be tuned separately without affecting the other mode. The whole SSPP slab is utilized as the radiator of the TM10 mode, while the air ring gap, the shorting pin, and a minor part of SSPP slab work as the radiator of the LC resonant mode. The compact size and the high radiation efficiency of the proposed antenna are due to the high field confinement and high effective refractive index of SSPPs. A reliable circuit model is first proposed for an SSPP antenna and applied to design it for dual-band operation. A prototype was fabricated using PCB technology and measured. The proposed antenna achieves a compact electrical size of $0.18lambda _{mathbf {0}} times 0.18lambda _{mathbf {0}} times 0.07lambda _{mathbf {0}}$ , which is significantly smaller than its counterparts ( $lambda _{mathbf {0}}$ is the wavelength at lower resonant frequency). Our proposed antenna possesses higher relative bandwidth per wavelength square area in comparison with other dual-band antennas. Both the simulated and measured results verified the high total efficiencies of the proposed dual-band antenna. The proposed antenna will have potential applications in wireless communication systems.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Compact Broadband Linearly Polarized Quincunx Metasurface Antennas Using
           Embedded Fractal Design

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      Authors: Meng Guo;Wei Wang;Fang Hao;Ping Huang;Linshu Gong;Xuefeng Song;
      Pages: 1081 - 1086
      Abstract: A quincunx metasurface (MTS) structure is presented and exploited to design compact broadband metasurface antennas (MTAs). The MTS patch unit is constructed by connecting five same-size quincunx-arrangement squares with strip lines. Since it is a fractal structure and structurally embedded with other units, the gap between adjacent units is prolonged, increasing the edge capacitance. Meanwhile, the surface current is adjusted to flow along the diagonal of quincunx patches, producing a large strip inductance. Hence, the resonance responding to the MTS radiator can be shifted to the low frequencies, while a compact radiating aperture can be obtained accordingly. With the help of characteristic mode analysis (CMA), the quincunx MTS array is modified for further miniaturization. Jerusalem cross aperture and four rectangle apertures are etched on the ground plane, generating aperture modes. Subsequently, the modified quincunx MTS is coupled to a U-shaped feeding network through apertures, forming a horizontally polarized MTA and realizing an operating bandwidth of 37.92% and a peak gain of 7.36 dBi with a compact radiating aperture of $0.34lambda _{0} times 0.34lambda _{0}$ . Ultimately, a 45° linearly polarized quincunx MTA using a double U-shaped feeding network is also proposed, obtaining a broader operating bandwidth of 44.60% and 6.43 dBi peak gain with $0.34lambda _{0} times 0.34lambda _{0}$ radiating aperture.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • W-Band Low-Profile Transmit Array Based on Wideband Partially Reflecting
           Surface

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      Authors: Hao Jiang;Jian Zhang;Fan Yang;Luming Zhang;Feiliang Chen;Mo Li;Zewei Wu;
      Pages: 1087 - 1092
      Abstract: This communication presents a wideband low profile transmit array (TA) with a small height-to-diameter (H/D) ratio of 0.285 working at a center frequency of 100 GHz, which consists of a waveguide feed source, a metal ground plane, a partially reflective surface (PRS), and a transmission surface (TS). A PRS with not only a positive reflection phase gradient, but also a negative transverse reflection magnitude gradient is designed above the ground plane to reduce the height as well as to broaden the bandwidth of the TA. The proposed TS is composed of eight unit cells (UCs) with a high transmission magnitude and phase differences of 45° in a broadband range. Four passive antenna prototypes with different beam directions are fabricated to validate the design concepts, and good agreements are obtained between the radiation patterns, gain curves, and return losses. The measured peak gain is 20.7 dBi with aperture efficiency (AE) of 10.5% at 99.5 GHz. A relative bandwidth of 15.2% is obtained within 3 dB gain variations, making it a promising candidate for sixth-generation (6G) wireless communication applications.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Low-Profile 2D Passive Phased-Array Antenna-in-Package for Emerging
           Millimeter-Wave Applications

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      Authors: Amir Raeesi;Ardeshir Palizban;Ahmad Ehsandar;Hussam Al-Saedi;Suren Gigoyan;Wael M. Abdel-Wahab;Safieddin Safavi-Naeini;
      Pages: 1093 - 1098
      Abstract: This article covers the implementation, calibration, and measurement aspects of a low-profile 4 $times $ 4 passive phased-array antenna-in-package (AiP) employing the beamformer discussed in [9]. The antenna array comprises slot-coupled patch antennas with left-handed circularly polarized (LHCP) radiation. Microelectromechanical system (MEMS)-like tunable phase shifter (PS) functioning based on controlling the phase constant of a slow wave microstrip line is employed for the phase tuning. Measurement results show the antenna‘s main beam can be steered over an angular range of ±30° in both elevation and azimuth planes. The operating frequency bandwidth of the system ranges from 28 to 30 GHz. The peak directivity and the radiation efficiency of the antenna system are 18.48 dBic and 58% at Boresight at 29 GHz, respectively. The efficiency drops 16% when the steering angle reaches the maximum.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Synthesis of Wideband Frequency-Invariant Beam Patterns for Nonuniformly
           Spaced Arrays by Generalized Alternating Projection Approach

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      Authors: Liyang Chen;Yanhui Liu;Shiwen Yang;Jun Hu;Y. Jay Guo;
      Pages: 1099 - 1104
      Abstract: This work generalizes the alternating projection approach (APA) to synthesize wideband frequency-invariant (FI) beam patterns for linear nonuniformly spaced arrays (NUSAs). Different from the conventional APA where excitation weights are synthesized for a desired pattern at single frequency, the generalized APA intends to find appropriate finite-impulse response (FIR) filter coefficients for each antenna element to provide the required wideband frequency-dependent excitation for a desired wideband FI pattern, and two modification techniques called mainlobe FI modification and wideband sidelobe control are introduced in each iteration to successively update the FI pattern performance. Several examples for synthesizing wideband FI beam patterns for NUSAs in different applications are conducted to verify the effectiveness and advantages of the proposed generalized APA.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Bandwidth Enhancement of the Millimeter-Wave Microstrip Linear Array With
           Loading of Shorting Pins

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      Authors: Lin Hai Xu;Yu Qing Guo;Peng Fei Hu;Kwok Wa Leung;Yong Mei Pan;
      Pages: 1105 - 1110
      Abstract: A broadband, series-fed, millimeter-wave (MMW) microstrip linear array is investigated. This array is evolved from a stub-loaded microstrip line, which has two resonant modes in the passband and an impedance bandwidth of about 26%. By simply inserting three pairs of shorting pins at the two ends of the microstrip line to regulate the field/current distributions, four additional resonances can be excited, significantly increasing the operating bandwidth to 63.5%. In addition, the original gain dips caused by anti-phase (equivalent) magnetic current disappear and the gain becomes quite stable, showing the maximum value of 12.82 dBi and a 3 dB bandwidth of 53.8%. Also, the first sidelobe level (FSLL) is lower than −10 dB from 26.6 to 44.2 GHz (49.7%) and lower than −20 dB from 26.6 to 30.7 GHz (14.3%). Therefore, the proposed array features great advantages, such as a simple structure and an enhanced bandwidth with good sidelobe suppression.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Ka-Band Huygens Antenna Array With Very High Aperture
           Efficiency and Low Sidelobes

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      Authors: Wei Lin;Richard W. Ziolkowski;
      Pages: 1111 - 1116
      Abstract: A Ka-band Huygens antenna array with extremely high aperture efficiency (AE) and low sidelobe levels is reported for 5G millimeter-wave (mm-wave) wireless applications. The basic array element is an innovative Huygens subarray consisting of two open rectangular waveguides that form an aperture consisting of a 1 $times $ 2 set of orthogonal, tightly coupled electric and magnetic elements separated by a virtual gap that are balanced, in- phase, and radiate Huygens cardioid patterns. A larger 8 $times16$ element array is then realized with 64 of these 1 $times $ 2 subarrays. With excitations of equal amplitude, the full broadside-radiating array achieves an AE up to 97.5% in the operating bandwidth, which is very close to the 100% limit associated with an ideal uniform aperture distribution. Moreover, a highly efficient and compact feed network with tapered-amplitude and in- phase excitations from the array center to its edges is designed to achieve sidelobe and backlobe levels less than −20 dB. The −10 dB impedance bandwidth covers 26.7–29.65 GHz, and the peak realized AE (RAE) reaches 82%. A full-aluminum array prototype was fabricated with standard machining processes and tested. The measured performance characteristics agree well with their simulated values, confirming the efficacy of their designs.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Ultra-Wideband Millimeter-Wave Bidirectional Circularly Polarized Monopole
           Antenna Array Using a Sequentially Rotated Feeding Technique

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      Authors: Chao Wang;Guanghui Xu;Minquan Li;Zhixiang Huang;Xingang Ren;Jingping Wang;Xianliang Wu;
      Pages: 1117 - 1122
      Abstract: In this communication, an ultrawideband millimeter-wave (mm-Wave) bidirectional circularly polarized (CP) monopole antenna array with sequential rotation feeding (SRF) technique is proposed. First, a broadband CP monopole antenna element is realized by utilizing the asymmetric ground plane, C-shaped ring, and rectangular stub structure. A microstrip to coplanar waveguide (CPW) transition structure is designed to feed the antenna element. Then, the SRF technique is adopted to further improve the axial ratio (AR) bandwidth of the 2 $times2$ CP subarray. Finally, a $4times4$ CP array is designed to further enhance the gain for mm-Wave applications. Measured results show that the proposed $4times4$ CP array exhibits the −10 dB impedance bandwidth of 102.7%, 3 dB AR bandwidths of 100.7%/101.3% in the $+textit {z}/-textit {z}$ -direction, and the peak gain of 15.6 dBic.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Coupling Mode Transformation-Based Dielectric Surface and Metasurface for
           Antenna Decoupler

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      Authors: Jiongjian Fang;Jinxin Li;Pei Xiao;Jun Dong;Gaoshen Li;Sichun Du;William T. Joines;
      Pages: 1123 - 1128
      Abstract: In this communication, a novel hybrid decoupler is proposed to reduce mutual coupling for an extremely compact wideband stacked patch multiple-input–multiple-output (MIMO) array antenna. The hybrid decoupler consists of a dielectric surface and a metasurface. By using a well-designed dielectric surface, the mode of mutual coupling current on the unexcited antenna can become orthogonal to its polarization mode. Moreover, the electrical distance of coupling wave propagation between two elements is prolonged. Antenna decoupling is naturally achieved. Then, the metasurface, which can reject coupling wave propagation, is a complementary method to further improve isolation. Dielectric rod array is designed by partially hollowing the dielectric surface, which can realize optimized dielectric constant of the slab and better combine two decoupling methods. A broadband stacked patch array antenna is chosen as a demonstration to prove that this idea can achieve wide isolation improved bandwidth, as well as high isolation improved degree. Measured results reveal that isolation enhancement ranges from 6 to 21 dB in the frequency band from 1.83 to 2.17 GHz.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Performance Improvement of Mechanically Beam-Steerable Transmitarray
           Antennas by Using Offset Unifocal Phase Symmetry

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      Authors: Peng Mei;Gert Frølund Pedersen;Shuai Zhang;
      Pages: 1129 - 1134
      Abstract: This communication presents the concept of offset unifocal phase symmetry to improve the performance (gain, gain roll-off, sidelobe level, etc.,) of mechanically beam-steerable transmitarray (TA) antennas. The phase shifts are initially determined from an offset feed source to make the corresponding TA antenna radiate a tilted beam with high gain. The phase shifts are asymmetric and can be broadly divided into dominant and ordinary phase shifts with respect to the offset feed source. By mirroring the dominant phase shifts to make the phase shifts symmetric, it can enable symmetric radiation beams for symmetric offset feed sources and improve phase error. When the offset feed source is moving inward to steer the main beam, the phase error of the phase-shifting surface with respect to the feed source starts to occur, while the electric-field spillover/illumination from the feed source is improved, which can maintain the gains of scanning beams. To verify the validity of the concept, the performance of a beam-steerable TA antenna enabled by the offset unifocal phase symmetry has been simulated and compared with the counterparts of unifocal and bifocal beam-steerable TA antennas. The measured results agree well with the simulated ones, revealing that the beam-steerable TA antenna enabled by the offset unifocal phase symmetry can maintain realized gains of scanning beams, suppress sidelobe levels, and reduce gain roll-off within the beam-scanning coverage. The offset unifocal phase symmetry, in principle, is a generalized approach and applicable to reflectarray antennas to improve the beam-steerable performance as well.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Liquid Crystal Tunable Metamaterial Unit Cell for Dynamic Metasurface
           Antennas

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      Authors: Peng-Yuan Wang;Benedikt Sievert;Jan Taro Svejda;Niels Benson;Fan-Yi Meng;Andreas Rennings;Daniel Erni;
      Pages: 1135 - 1140
      Abstract: This communication presents a liquid crystal (LC)-based electronically tunable metamaterial unit cell that can serve as a building block for dynamic metasurface antennas (DMAs). The metamaterial unit cell was designed based on a complementary electric-inductive-capacitive (cELC) resonator, whose structure was modified into double metal layers for ease of loading the LC mixture. The equivalent capacitance, and thus the transmission coefficient of the metamaterial unit cell, can be tuned by external biasing voltages. The metamaterial unit cell couples to the transverse magnetic (TM) field, making it easy to be embedded into waveguide-fed structures such as microstrip lines or parallel-plate waveguides. In addition, it is individually addressable, which meets the design requirement of DMAs. Experimental results show that the transmission coefficient of the metamaterial unit cell can be continuously tuned from −2.7 to −6.5 dB at 29 GHz with a biasing voltage swinging from 2.5 to 10 Vrms. The response times are around 150 ms for both switch-ON and swtich-OFF cases.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • An Extension of Partial Element Equivalent Circuit Method for Frequency
           Selective Surface Analysis

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      Authors: Zhong-Xiang Wang;Peng-Chao Zhao;Zhi-Yuan Zong;Wen Wu;Da-Gang Fang;
      Pages: 1141 - 1146
      Abstract: In this communication, an extension of a partial element equivalent circuit (PEEC) method for frequency selective surfaces (FSSs) modeling is presented. Based on Floquet’s theorem and dyadic periodic Green’s functions of a layered medium, the general PEEC formulations and models for periodical structures are deduced, and Poisson’s sum formula is used to improve the convergence speed. Furthermore, the extension is also performed by developing a normalized-current-based simplified PEEC (NCB simplified PEEC), which can accelerate the calculation of the scattering coefficients significantly. Also, the circuit parameters within the interested frequency band are related to the FSS geometric parameters, which is beneficial to the optimization of FSS. The scattering coefficients of both patch and slot FSSs with a dielectric substrate are calculated, which agree well with those calculated by electromagnetic simulation software Altair FEKO 2020.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Rigorous Solution to Electromagnetic Wave Diffraction by Junctions of
           Impedance and Semitransparent Surfaces

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      Authors: Kirill Klionovski;Sergey Bankov;
      Pages: 1147 - 1151
      Abstract: Recent studies of surface-wave-based waveguides for terahertz (THz) imaging and spectroscopy have displayed some interest in investigating surface-wave diffraction by junctions of surfaces with different boundary conditions. Generally, many practically applicable surfaces for THz surface waveguides can be described using nontransparent or semitransparent impedance boundary conditions. In this communication, we find rigorous solutions to electromagnetic wave diffraction by the junction of a nontransparent impedance wedge and a semitransparent half-plane, as well as the junction of two semitransparent half-planes. Generalized semitransparent boundary conditions characterize these semitransparent surfaces.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Implementing the Fast Full-Wave Electromagnetic Forward Solver Using the
           Deep Convolutional Encoder-Decoder Architecture

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      Authors: He Ming Yao;Lijun Jiang;Michael Ng;
      Pages: 1152 - 1157
      Abstract: In this communication, a novel deep learning (DL)-based solver is proposed for the electromagnetic forward (EMF) process. It is based on the complex-valued deep convolutional neural networks (DConvNets) comprising an encoder network and a corresponding decoder network with pixel-wise regression layer. The encoder network takes the incident EM wave and the contrast (permittivity) distribution of the object as the input. It channels the processed data into the corresponding decoder network to predict the total EM field due to the scatter of the input incident EM wave. The training of the proposed DConvNets is done using the simple synthetic dataset. Due to its strong approximation capability, the proposed DConvNets can realize the prediction of EM field. Hence, the proposed DL-based EMF solver acts as a “inhomogeneous” transformation—the unknown EM field in the objective domain is obtained through the transformation from the information of the incident EM field and the distribution of contrasts (permittivities). Compared with conventional methods, the EMF problem can be solved with higher accuracy and significantly reduced CPU time. Numerical examples have demonstrated the feasibility of this newly proposed approach. This newly proposed DL-based EMF solver presents a new alternative to electromagnetic computation approaches.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Robust Grid-Based Computation of H-Matrix Blocks’ Low-Rank Approximation
           for Vector Basis Functions

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      Authors: Jon T. Kelley;Ali Yilmaz;Yaniv Brick;
      Pages: 1158 - 1163
      Abstract: A fast method to assess and correct the domain misrepresentation of impedance matrix blocks, $mathrm {Z}^{mathrm {os}}$ , based on their row- and column-sampling, to ensure the accuracy of their low-rank approximation (LRA), is presented. The misrepresentation arises when auxiliary grid-based interaction matrices, $mathbf {G}$ , of smaller dimensions are used to replace $mathrm {Z}^{mathrm {os}}$ to accelerate their LRA. Specifically, a recently introduced fast multilevel LRA algorithm, which uses truncated singluar-value decompositions of matrices corresponding to interactions between basis-functions and proxy grids, is shown to lose error controllability when used for vector basis/testing functions. A pre-processing stage that correctly and automatically sets the algorithm’s truncation threshold, $tau _{mathcal {G}}$ , for $mathbf {G}$ , such that the domains of their truncated versions represent those of the blocks to the desired accuracy, is proposed. The method first analyzes small, randomly sampled portions of $mathbf {G}$ and $mathrm {Z}^{mathrm {os}}$ , increasing the sample size until their spectrums converge; it then uses the converged spectra to gradually increase the rank and lower the truncation threshold, until the desired error level is achieved. The resulting truncation threshold, $bar {tau }$ , is then used for $tau _{mathcal {G}}$ across all algorithm levels. Representative examples validate the method and show its effectiveness.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Spatial Radiation Field Distribution of Underwater VLF Two-Element Antenna
           Array

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      Authors: Mingyue Yang;Huaiyun Peng;Kuisong Zheng;Gao Wei;
      Pages: 1164 - 1169
      Abstract: In this communication, we analyze the field distributions of underwater very-low-frequency (VLF) two-element array composed of two symmetrical antennas. This analysis is carried out with the improved parallel total-field scattered-field source (TSS) finite-difference time-domain (FDTD) method with sea–air boundary field value conversion and thin-wire algorithm. We specifically analyze the field distribution in the range close to the antenna array in seawater. Furthermore, we also study the field propagation law in air propagating across the air–sea interface.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Exact Evaluation of Time-Domain Physical Optics Integral for High-Order
           Triangles

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      Authors: Aslihan Aktepe;Hüseyin Arda Ülkü;
      Pages: 1170 - 1173
      Abstract: In this work, a method for the exact evaluation of time domain physical optics (PO) integral on high-order triangles is presented. The presented method is based on the recently developed method for quadratic triangles. Specifically, the PO integral on the surface of the high-order triangle is reduced to a line integral on the intersection of the high-order triangle and the plane formed by the incidence and observation directions in barycentric coordinates of the triangle. Then, the intersecting curve is parametrized in terms of one of the barycentric coordinates of the high-order triangle. At last, the line integral is evaluated exactly using the suitable order Gauss Legendre quadrature rule (GLQR). The validity of the proposed method is demonstrated via analyzing transient scattering from a unit sphere and a flower-shaped scatterer modeled with high-order triangles using PO approximation.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • EM Scattering by Gyrotropic Circular Cylinders With Arbitrarily Oriented
           External Magnetic Bias

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      Authors: Grigorios P. Zouros;Konstantinos Katsinos;
      Pages: 1174 - 1179
      Abstract: We extend a developed coupled-field volume integral equation (CFVIE) method to solve the electromagnetic (EM) scattering by a gyrotropic circular cylinder, under normal incidence, with arbitrarily oriented external magnetic bias. When the magnetic bias is not aligned with cylinder’s axis, the permittivity and permeability are described by fully populated tensors. As a consequence, the total fields cannot be separated to ${mathrm{ TE}}^{{z}}$ and ${mathrm{ TM}}^{{z}}$ but, instead, are hybrid. The CFVIE is then solved by the cylindrical Dini series expansion (CDSE) method. We validate the extended CFVIE with the HFSS commercial software, and we report on the complex natural frequencies of ferrite (i.e., gyromagnetic) cylindrical resonators magnetized under oblique magnetic bias.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • A Deep Learning Approach for Reconstruction in Millimeter-Wave Imaging
           Systems

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      Authors: Peyman Rostami;Hojatollah Zamani;Mohammad Fakharzadeh;Arash Amini;Farokh Marvasti;
      Pages: 1180 - 1184
      Abstract: In millimeter-wave (MMW) imaging, the objects of interest are oftentimes modeled as 2-D binary (black and white) shapes with white pixels representing the reflecting interior of the object. However, due to the propagation of the scattered waves, the continuous-domain binary images are convolved with a so-called point-spread function (PSF) before being digitized by means of sampling. As the 2-D PSF is both nonseparable and nonvanishing in the case of MMW imaging, exact recovery is quite complicated. In this communication, we propose a deep-learning approach for image reconstruction. We should highlight that the wave scatterings are suitably represented with complex-valued quantities, while standard deep neural networks (DNNs) accept real-valued inputs. To overcome this challenge, we separate the real and imaginary parts as if we had two imaging modalities and concatenate them to form a real-valued input with a larger size. Fortunately, the network automatically learns how to combine the mutual information between these modalities to reconstruct the final image. Among the advantages of the proposed method are improved robustness against additive noise and mismatch errors of imaging frequency and object to antenna distance; indeed, the method works well in wideband imaging scenarios over a wide range of objects to antenna distances even in the presence of high noise levels without requiring a separate calibration stage. We test the method with synthetic data simulated with software as well as real recordings in the laboratory.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Nondestructive Testing Using mm-Wave Sparse Imaging Verified for Singly
           Curved Composite Panels

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      Authors: Niklas Wingren;Daniel Sjöberg;
      Pages: 1185 - 1189
      Abstract: Nondestructive testing (NDT) of composite materials is important in aerospace applications, and millimeter-wave (mm-wave) imaging has been increasingly used for this purpose. Imaging is traditionally performed using Fourier methods, with inverse methods being an alternative. This communication presents an mm-wave imaging method with an inverse approach intended for NDT of singly curved composite panels with sparsely distributed flaws. It builds on previous work which was limited to imaging on planar panels. The move from planar to singly curved panels increases the applicability of the method for aerospace applications. The imaging method is reference-free due to a numerical source separation algorithm and exploits sparsity in the reconstruction of scatterers. It is demonstrated using near-field measurements at 60 GHz of an industrially manufactured composite panel with deliberate flaws. Compared to a more traditional Fourier imaging method, our method generates images with higher resolution and higher dynamic range. Flaw detection is also easier using our method as it generates images with less background clutter.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • Special Issue Measurement Technologies for Emerging 5G and Beyond Channel
           Characterization and Antenna Systems

    • Free pre-print version: Loading...

      Pages: 1190 - 1190
      Abstract: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • TechRxiv: Share Your Preprint Research with the World!

    • Free pre-print version: Loading...

      Pages: 1191 - 1191
      Abstract: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
  • IEEE Open Access

    • Free pre-print version: Loading...

      Pages: 1192 - 1192
      Abstract: Presents information on the above named publication.
      PubDate: Jan. 2023
      Issue No: Vol. 71, No. 1 (2023)
       
 
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