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

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      Pages: C2 - C2
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • IEEE Transactions on Antennas and Propagation

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      Pages: C3 - C3
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Institutional Listings

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      Pages: C4 - C4
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Pattern Synthesis for Lossy Antennas Based on N-Port
           Characteristic Mode Analysis

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      Authors: Hui Li;Wenrui Zheng;Qi Wu;Guo-Lin Liu;
      Pages: 4628 - 4639
      Abstract: In this article, a pattern synthesis methodology for lossy antennas is proposed based on ${N}$ -port characteristic mode analysis (CMA), with the radiation efficiency of the antenna guaranteed at the same time. Reactive loads are chosen as physical implementations. To perform $N$ -port CMA, $N$ ports are first added to the lossy and lossless structures to obtain the impedance matrices. Modal efficiencies are then calculated, based on which the locations of the feed and the loads are selected. With the characteristic solutions and one set of modal weighting coefficients (MWCs), where inefficient modes have been excluded, the corresponding loads and radiation pattern can be determined. Afterward, an objective function considering physical implementation and the target pattern is established and optimized. With optimal MWCs, the lumped components loaded at each port are calculated and implemented. The method is applied to an arm-worn smartwatch antenna operating at GPS L1 band, which aims at radiating toward the sky direction for reliable link with satellites. Following the proposed method, the power radiated toward the target area has been increased by more than 40% compared with the original design. The total efficiency is above −6.1 dB when it is worn on a Cellular Telecommunications Industry Association (CTIA) arm. The prototype of the proposed antenna (Prop. Ant) has been fabricated and measured, which showed similar performances to the simulated one both in free space and in the arm-worn scenario.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Finite Element Analysis and Optimization of Acoustically Actuated
           Magnetoelectric Microantennas

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      Authors: Xinyu Cai;Kaihang Zhang;Tongxiang Zhao;Zhentao Yu;Jie Liang;Yihong Zhang;Haobin Wang;Hao Jin;Shurong Dong;Weipeng Xuan;Yungui Ma;Andrew J. Flewitt;Jikui Luo;
      Pages: 4640 - 4650
      Abstract: The acoustically actuated magnetoelectric (ME) microantenna integrated on a film bulk acoustic resonator (FBAR) has exhibited a potential for communication and wireless sensing applications owing to the breakage of traditional antenna size limitation. However, the development is still at infancy, and much is unknown and unclear for the design of the ME microantennas and material selection. This article presents a finite element analysis-based method and a magnetic dipole model to analyze the radiation characteristics of ME antenna. The effects of piezoelectric (PE) and magnetostrictive (MS) materials and their thicknesses, shape, and area of the electrode, and damping factor of the MS material on the radiation characteristics of ME antenna are investigated in detail. Results show that with an optimized design and proper materials combination, FBARs with an ME microantenna of the size $200,, {}times {}200mu text{m}$ could emit electromagnetic waves over 30 m with a maximum radiation power of up to $3.4,, {}times {}10^{-7}$ W (−34.7 dBm), suitable for short-range communication and wireless sensing applications, demonstrating a great potential of the ME microantennas.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Design of Dual-Band Antenna for Metal-Bezel Smartwatches With Circular
           Polarization in GPS Band and Low Wrist Effect

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      Authors: Zhensen Xu;Yan Wang;
      Pages: 4651 - 4662
      Abstract: A dual-band antenna with circularly polarized (CP) in GPS band and low wrist effect for metal-bezel smartwatches is proposed and studied in this article. The proposed antenna consists of a metal ring, a capacitor, a system ground plane with a feeding network, and a metal plane. The dual-band operation with CP in the GPS band is analyzed based on the theory of characteristic mode (TCM), where the CP is achieved by the capacitor. The low wrist effect, which is analyzed based on the electric-field distributions, is realized by a metal plane. On the wrist, with the help of the metal plane, the antenna efficiencies are improved from −9.8 to −6 and from −7.3 to −4.6 dB in the GPS and WiFi/Bluetooth (BT) bands, respectively. In addition, the AR in the GPS band is improved from 4.5 to 2.4 dB. A prototype shows that, on the wrist, the measured return loss is better than 8.6 and 6.7 dB in the GPS and WiFi/BT bands, respectively. The measured efficiencies are −6.6 and −5 dB, respectively, in the two bands. The measured 3-dB AR bandwidth is 30 MHz (1558–1588 MHz). In addition, the proposed antenna has a stable performance on the wrist. The dual-band antenna with high efficiencies in the GPS and WiFi/BT bands, good AR in the GPS band, and stable performance on the human wrist, is promising for practical application.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A General Optimization Method for Complex Requirements Antenna Based on
           Balanced Demotion MOEA

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      Authors: Fengling Peng;Xing Chen;
      Pages: 4663 - 4674
      Abstract: A general multiobjective evolutionary algorithm (MOEA) is presented to solve the antenna optimization problem with complex requirements. By analyzing the common requirements in the antenna design process, a strategy of calculating the difference between the indicator value and the threshold is applied to construct the objective units that can accurately evaluate the antenna performance and reconstruct the objective functions quickly. The fitness functions can solve the fuzzy requirements problem. An adaptive mechanism is designed for mutation and crossover operation in order to balance the convergence rate and the ability to avoid local extremes. In nondominated sorting, the crowding calculation method is improved so that the individuals can be dispersed in the objective space. A demotion mechanism is designed for the selection operation to balance the importance of all objective functions and constraints. It can not only make the optimal solution closer to the actual requirement but also reduce the computation cost of the algorithm itself. Then, this algorithm is applied to an ultrawideband (UWB) dipole antenna with complex requirements as a case study. Analyzing the optimization results shows that all the indicators of the antenna optimized by the algorithm can well satisfy the actual requirements.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Millimeter-Wave Co-Polarized In-Band Full-Duplex Antenna Based on a Mode
           Superposition Method

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      Authors: Chao Jun Ma;Shao Yong Zheng;Yong Mei Pan;
      Pages: 4675 - 4685
      Abstract: In this article, a novel mode superposition method is proposed to implement a millimeter-wave (MMW) shared-radiator co-polarized in-band full-duplex (IBFD) antenna at 29 GHz. The proposed method is realized based on a dielectric resonator antenna (DRA). By simultaneously exciting the TM $_{01delta }$ and HEM $_{21delta }$ modes of a DRA, a superposed mode with a field pattern analogous to the TE211 mode can be produced. Since both the transmitter (TX) and the receiver (RX) ports locate at the weak-field regions of the superposed mode, a decoupling performance is therefore obtained without the use of any additional decoupling structures or circuits. For validation, a DRA with artificial electromagnetic boundaries (AEMBs) is employed, so that the TM $_{01delta }$ and HEM $_{21delta }$ modes can be simultaneously excited using a simple microstrip proximity coupling. It only needs to properly adjust the geometric parameters of the DRA, and the mutual coupling is substantially suppressed. The experiment demonstrates that the antenna can achieve maximum isolation of 42 dB and peak gain of 8.65 dBi. Due to the simple and integrated architecture, the proposed method is promising for MMW IBFD applications.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Mutual Coupling Suppression Between Two Closely Placed Patch Antennas
           Using Higher-Order Modes

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      Authors: Jian-Feng Qian;Steven Gao;Benito Sanz-Izquierdo;Hanyang Wang;Hai Zhou;Huiliang Xu;
      Pages: 4686 - 4694
      Abstract: This article presents a novel method for decoupling two patch antennas. Instead of using the TM $_{mathbf {10}}$ mode of a conventional patch, TM $_{mathbf {20}}$ mode is utilized as the operation mode of the antenna. By loading stubs at the radiating edge of the patch, the resonance frequency of the TM $_{mathbf {20}}$ mode is moved down to the same band as the original TM $_{mathbf {10}}$ mode. Then, the mutual coupling between two such patch antennas is suppressed simply by physical placement, even when they are placed extremely close to each other. Without using any extra decoupling elements, isolation is improved by up to 20 dB using this method. Furthermore, this method can also be applied to multielement multi-input -multi-output (MIMO) array and dual-antenna system with different operating bands. The proposed method is verified with three different application scenarios, including a two-element MIMO array, a two-antenna system with adjacent operating bands, and a four-element MIMO array. Reasonable agreements between simulated and measured results can be observed, showing the advantages of simple structure, low cost, high isolation, and good radiation performance.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Sparse Antenna Array With Flat-Top and Sharp Cutoff Radiation Patterns

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      Authors: Mingming Xu;Chen Zhang;Haidong Qiao;Qingjun Zhang;Changjiang Deng;Weihua Yu;
      Pages: 4695 - 4703
      Abstract: A sparse antenna array with flat-top and sharp cutoff radiation patterns is presented in this work. The array consists of 16 antenna elements, which is realized by applying a symmetrical sparse configuration with uniform excitation phase. This configuration simplifies the excitations of the array while maintaining excellent radiation performance. The dual-band dual-polarized base station antenna based on the proposed sparse antenna arrays in the bands of 1.71–2.17 and 2.30–2.69 GHz is fabricated and measured. The measured results are in very good agreement with the predicted ones, showing that the port reflection coefficient is less than −15.0 dB, and the isolation is greater than 28.5 dB. In addition, the array has a gain of 10.1–12.3 dB, a half-power beamwidth (HPBW) of $45^{circ } pm 5^{circ }$ in both the horizontal and vertical planes, a cutoff transition of less than 17.4° from −3 to −20 dB between the main beam and the sidelobe area, and a sidelobe level suppressed to below −21.1 dB. Apart from the good radiation performance, the proposed sparse antenna array has a compact size with very few antenna elements, which is very suitable for communication in a crowded scene.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Miniaturized Pattern-Reconfigurable Multimode Antennas With Continuous
           Beam-Steering Capability

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      Authors: Tian Liang;Yongsheng Pan;Yuandan Dong;
      Pages: 4704 - 4713
      Abstract: In this article, two miniaturized multimode pattern-steering antennas for Internet of Things (IoT) applications are proposed. A compact multimode cavity functions both the hybrid and the radiator. A continuous 360° pattern scanning in the azimuth plane is controlled by the amplitude and phase of three excitation ports. The first design achieves the smallest size with TM02 and TM11 modes. In contrast, the second design has improved impedance bandwidth and mode isolation by introducing TM02 and high-order TM21 modes. Eight dipole chokes are attached to the cavity for surface current suppression. This approach eliminates the unwanted patch mode radiation. The antennas support multibeam applications with digital beamforming and analog beamforming with the 0°/180° phase switch and variable gain amplifier (VGA). The direction of arrival (DOA) can be estimated by directly measuring the amplitude and phase of the receiving signal. No full phase shifter and signal classification algorithm are required. The prototypes are fabricated and measured at 2.4 GHz. The diameters of the two antennas are $0.4~lambda 0$ and $0.9~lambda 0$ . The achieved antenna size is very miniature as shown by the literature comparison. The radiation and DOA performance is evaluated. The peak system efficiency is better than 60% after calibration and a good DOA estimation result is obtained.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Assessment of the Robustness of Flexible Antennas to Complex Deformations

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      Authors: Ekrem Altinozen;Ana Vukovic;Phillip Sewell;
      Pages: 4714 - 4723
      Abstract: Wearable antennas can suffer from a variety of mechanical deformations that are induced by the body dynamic. The article analyses how these complex deformations impact the performance of a flexible antenna operating in the 5–6 GHz band. The Green Coordinates (GC) spatial manipulation technique is used to generate a range of complex 2-D deformations, namely spherical, saddle, and twisting deformation. Generating full geometries is a key enabler in this study. The results offer valuable insight into the stability of antenna performance under in situ deformations.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Printed Metasurface Leaky Wave Antennas Based on Penetrable Aperture Field
           Synthesis

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      Authors: Hakjune Lee;Do-Hoon Kwon;
      Pages: 4724 - 4736
      Abstract: A design methodology for 1-D modulated printed metasurface leaky wave antennas (LWAs) with a pattern synthesis capability in 2-D TE polarization is presented. For a desired radiation pattern, complete tangential fields on the surface of a grounded dielectric substrate are constructed and optimized to find a pointwise passive surface impedance distribution. Dielectric and conductor losses are considered in the field synthesis process via a design curve obtained using analysis of a physical unit cell with lossy constituents. It enables accurate prediction of the aperture field distribution when practical lossy materials are used. A spatially modulated impedance can be realized using an array of printed copper strips. Three 10-wavelength-long LWA designs are demonstrated numerically for broadside, two-beam, and sector patterns. The LWA for broadside radiation is fabricated and measured, showing a good agreement with the simulation results.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Chiral Metasurface Enabled Circularly Polarized OAM-Generating Folded
           Transmitarray Antenna With High-Gain Low-Profile and Broadband
           Characteristics

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      Authors: Dashuang Liao;Xue Ren;Liqiao Jing;Min Li;Hongsheng Chen;Zuojia Wang;
      Pages: 4737 - 4746
      Abstract: A broadband low-profile high-gain folded transmitarray antenna (FTA) is proposed to generate orbital angular momentum (OAM) with circular polarization. A chiral metasurface is employed as the top layer with the function of reflecting anticipant circularly polarized (CP) incident waves while transmitting the orthogonal ones. The geometric phase is then introduced to achieve 360° coverage of the transmission phase without affecting the reflection one. To obtain a high-gain and compact planar source, a $2times2$ patch antenna array, integrated with the bottom metallic ground, is selected as the feed. Two proof-of-concept prototypes for vortex beam generation are constructed and experimentally measured. Both simulated and measured results demonstrate that $l=-1$ and +1 OAM mode beams can be generated from 8.7 to 9.5 GHz, and the measured maximum gains for $l=-1$ and +1 reach 18.1 and 18.3 dBi with the corresponding peak aperture efficiencies of 6.1% and 6.4%, respectively. Meanwhile, the axial ratios (ARs) of the peak of far-field patterns are less than 3 dB over the entire operating frequency range, providing broadband CP vortex beams. The proposed high-gain low-profile broadband FTA antenna shows a promising perspective in OAM-based wireless communication.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • An Effective Method for Antenna Radiation Pattern Reconstruction Based on
           Phaseless Measurement in a Reverberation Chamber

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      Authors: Fangyun Peng;Xiaobo Liu;Junhao Zheng;Ruihai Chen;Shitao Zhu;Xiaoming Chen;
      Pages: 4747 - 4758
      Abstract: It has been shown that the angular correlation of the antenna can be obtained by rotating it in a reverberation chamber (RC), and the radiation pattern of the antenna under test (AUT) can be reconstructed from the measured correlation coefficients using spherical wave decomposition. However, the correlation coefficient needs to be obtained by measuring the complex-valued S-parameters in an RC, which is no longer applicable to active antenna tests where the phase information is unavailable. To solve this problem, we propose an antenna radiation pattern reconstruction method based on phaseless measurement in an RC. In this method, the power correlation coefficient of AUT is calculated using the signal amplitude received by the antenna at different angles. According to the relationship between complex correlation coefficient and power correlation coefficient of the AUT, the nonlinear least squares method is used to reverse the spherical wave coefficients and reconstruct the antenna radiation pattern. Simulations and measurements are carried out in RC and anechoic chamber (AC), which demonstrated the feasibility and applicability of the proposed method.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Compact Dual-Band Implantable Antenna for Wireless Biotelemetry in
           Arteriovenous Grafts

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      Authors: Jungang Zhang;Rupam Das;Daniel Hoare;Huxi Wang;Afesomeh Ofiare;Nosrat Mirzai;John Mercer;Hadi Heidari;
      Pages: 4759 - 4771
      Abstract: Arteriovenous grafts (AVGs) are indispensable life-saving implants for chronic kidney disease (CKD) patients undergoing hemodialysis (HD). However, AVGs will often fail due to postoperative complications, such as cellular accumulation termed restenosis, blood clots, and infections, which are dominant causes of morbidity and mortality. A new generation of HD implants equipped with biosensors and multiband antennas for wireless power and telemetry systems that can detect specific pathological parameters and report AVGs’ patency would be transformative for CKD. Our study proposes a compact dual-band implantable antenna for HD monitoring applications. It operates in 1.4 and 2.45 GHz for wireless power transfer and biotelemetry purposes. The miniaturized antenna with a current size of $5times 5times0.635$ mm3 exhibits wide bandwidth (300 MHz at 1.4-GHz band and 380 MHz at 2.45-GHz band), along with good impedance matching at two resonance frequencies. In addition, simulations are performed separately in a three-layer homogenous phantom and a realistic human body model. Measurements of the proposed antenna are evaluated in minced pork. The measured results of the fabricated antenna prototype are closely harmonized with the simulation ones, and the effect of different proportions of fat tissue in pork mince was analyzed to verify the sensitivity of the antenna to the contacting medium. The specific absorption rate (SAR) and link budget calculation are also analyzed. Finally, the wireless biotelemetry function of the proposed antenna is realized and visualized by adopting a pair of nRF24L01 wireless transceivers, and sustainable and stable wireless data transmission characteristics are shown at a high data rate of 2 Mb/s with up to 20-cm transmission distance.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Shared Aperture 4G LTE and 5G mm-Wave Antenna in Mobile Phones With
           Enhanced mm-Wave Radiation in the Display Direction

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      Authors: Yan Wang;Feng Xu;
      Pages: 4772 - 4782
      Abstract: Radiation in the display direction of the 5G millimeter-wave (mm-wave) antenna in mobile phones is challenging due to the obstruction from the display. In this article, a shared aperture 4G LTE and 5G mm-wave antenna in mobile phones with enhanced mm-wave radiation in the display direction is studied. The 5G mm-wave array, consisting of four slot elements, is constructed in the clearance of a 4G LTE antenna. For the shared aperture design, the interdigital coupling (IDC) structure, which has a slight effect on the 4G LTE antenna, is used as the ground of the slot element. To enhance the mm-wave radiation in the display direction, two groups of floating patches are applied. For the 4G LTE antenna, the measured −6 dB impedance bandwidths are 280 MHz (700–980 MHz) and 1220 MHz (1700–2920 MHz). The measured efficiency is higher than 40%. For the 5G mm-wave array, the measured overlapped −10 dB impedance bandwidth is 2.7 GHz (25.1–27.8 GHz). The measured mutual coupling among each element is lower than −16 dB. Within the 25.5–27.5 GHz, in the display direction, the measured peak gain is 10.4 dBi, and the 3 dB beam steering range reaches 90° (45°– 135°) with a gain higher than 7.5 dBi.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Modal Expansion Analysis, Inverse Design, and Experimental Verification of
           a Broadband High-Aperture Efficiency Circular Short Backfire Antenna
           Loaded With Anisotropic Impedance Surfaces

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      Authors: Mengyuan Bie;Manxin Peng;Zhi Hao Jiang;Douglas H. Werner;
      Pages: 4783 - 4798
      Abstract: In this article, a broadband highly efficient circular short backfire antenna (SBFA) loaded with cylindrical anisotropic impedance surfaces (AISs) is proposed. An efficient modal expansion method (MEM) is developed to facilitate the analysis of the AIS-loaded SBFA with a finite-sized flange, which considerably reduces the computational resources as compared to commercial full-wave solvers. By combining the MEM with a multiobjective genetic algorithm, the geometrical dimensions of the antenna and the dispersive properties of the AIS are optimized through an inverse design strategy. As a proof-of-concept example, an S-band AIS-loaded SBFA with a broad bandwidth and high aperture efficiency is demonstrated, showing a good agreement between measured results and simulation predictions. An aperture efficiency of greater than 83% is experimentally achieved over a broad $S_{11} < -10$ dB bandwidth of 35.3%, with a peak aperture efficiency of about 100%. Moreover, the underlying operating principle of the antenna is revealed by the investigation of the main propagating modes in the SBFA. The extraordinary performance demonstrates that the proposed AIS-loaded SBFA represents a promising candidate for various wireless communication systems.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Wideband Shared-Radiator Four-Element MIMO Antenna Module for 5G Mobile
           Terminals

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      Authors: Xiaoying Tian;Zhengwei Du;
      Pages: 4799 - 4811
      Abstract: A low-profile wideband shared-radiator four-element multiple-input multiple-output (MIMO) antenna module that can be directly and flexibly integrated with the chassis ground of a mobile terminal is proposed. The module structure of a grounded square shared patch surrounded by four corner-cut patches is constructed through the characteristic mode analysis (CMA). By analyzing the low efficiency problem caused by the reverse currents, the off-diagonal feed positions are proposed to enhance the efficiency. The use of the shared patch with four I-shaped slots and the off-diagonal feeds makes the dimension of the proposed four-element antenna module only $30times 30times $ 2 mm3. With the help of multiple regionalized characteristic currents and four grounded short branches, the proposed antenna module shows good simulated isolations of better than 12.5 dB in the −6 dB impedance operating band of 4.25–5.13 GHz. To verify the integration flexibility, an $8times $ 8 MIMO antenna prototype with two proposed modules directly deployed on a phone-size chassis ground was fabricated and measured. The experimental results indicate that the −6 dB impedance operating band can cover the fifth-generation (5G) N79 band (4.4–5 GHz) with isolations of better than 10 dB and efficiencies of 40.3%–48.5%. The diversity performance, the channel capacity, the effects of the user’s hands and head on the antenna performance, and the specific absorption rate (SAR) are analyzed, and the results are acceptable. With the advantages of zero clearance, small size, wide bandwidth, isolation adjustment flexibility, and integration flexibility, the proposed antenna module is potentially applicable in future -obile terminals.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A CRLH-TL Inspired Dual-Band Antenna With Polarization Diversity for
           Wrist-Worn Wireless Body Area Network Devices

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      Authors: Buyun Wang;Sen Yan;Yuchen He;
      Pages: 4812 - 4822
      Abstract: A wrist-worn dual-band smartwatch antenna with polarization diversity is proposed for smartwatches. The antenna has a cylindrical structure with a diameter of 33.6 mm and a height of 6.8 mm. The radiated structure is inspired by composite right-/left-handed transmission lines (CRLH-TLs) to realize a dual-band operation (2.4 and 5.8 GHz WLAN band). The unit cell of the CRLH-TL is analyzed, and its equivalent circuit model and the dispersion curves are studied for mode analyzation. The +1 and −1 modes of CRLH TL are employed for dual-band operating, and two orthogonal-polarized modes are excited with different types of feeding structure to realize the polarization diversity with low coupling and low envelope correlation coefficients (ECCs). The wrist model is built in both simulation and experiment to evaluate the performance of the antenna, which shows a good radiation and diversity performances. The measured degree of freedom (DoF) is 1.92 and the capacity is 17.39 bit/s/Hz with 30 dB signal-noise rate (SNR). The results of specific absorption rate (SAR) are also studied and they are pretty low. These characteristics of the proposed antenna make it a competitive candidate for wrist-worn wireless body area network (WBAN) devices.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Circularly Polarized Metasurface Phased Array Antenna System With Wide
           Axial-Ratio Beamwidth for LEO Mobile Satellite Communication

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      Authors: Yingsong Zhang;Wei Hong;Zhidan Ding;Long Yang;Cheng Zhu;Yun Hu;
      Pages: 4823 - 4833
      Abstract: In this article, a millimeter-wave LHCP $1times32$ with a dummy on both sides phased array antenna is proposed. Multilayer structure and single feed are employed. The antenna patch adopts a $3times $ 3 metasurface. The measured impedance bandwidth is 20%, ranging from 22.5 to 27.5 GHz. The axial ratio (AR) bandwidth with an AR level < 3 dB achieves 3.35 GHz ranging from 24.15 to 27.5 GHz. Relative 3-dB AR bandwidth reaches 13.4%. A total of 37 beams were measured in the anechoic chamber. The results show that whether the phased array antenna system serves as transmitter or receiver, the 3-dB beam angle coverage at 26 GHz reaches from −42° to 45° at $varphi $ = 0° and from −42° to 42° at $varphi $ = 90°. The 3-dB AR beam angle ranges from −80° to 89° at $varphi $ = 0°, and from −45° to 45° at $varphi $ = 90°. Based on this linear array, it is easy to expand to circular polarization planar wide-angle scanning phased array. The antenna system realizes circular polarization with wide angle wide AR beam scanning, which can be used in low Earth orbit (LEO) satellite communication system.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Code-Dependent Beam Shaping and Polarization Control by Binary
           Transmitarray

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      Authors: Xiang Wan;Bai Yang Li;Wen Hao Wang;Zi Ai Huang;Jia Wei Wang;Xu Jie Wang;Qiang Cheng;Tie Jun Cui;
      Pages: 4834 - 4842
      Abstract: A code-dependent methodology is proposed to realize beam shaping and polarization control simultaneously by using binary transmitarray (BTA). The BTA unit elements are divided into two types, which are linearly polarized in orthogonal directions. By individually designing binary code for each type of unit elements, the radiation pattern and polarization of the synthetic field can be simultaneously defined. To verify this mechanism, four BTAs are designed at Ka-band with the same structures but with different binary codes to produce broadside directional beams with horizontal, vertical, left-handed circular, and right-handed circular polarizations, respectively. Furthermore, another BTA is designed to produce two directional beams pointing at different directions with left-handed and right-handed circular polarizations, respectively. Both simulations and measurements have verified that the proposed methodology provides a completely code-dependent mechanism to arbitrarily and independently design radiation patterns and polarizations of the BTAs. This methodology can be readily used to design binary programmable transmit arrays by integrating p-i-n or varactor diodes to the unit elements, so that radiation patterns and polarizations of the transmit arrays can be dynamically configured by merely changing the aperture codes, hence showing great values and potentials in communication and radar applications.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Leay Wave Antenna With Dielectric Superstrate on Perforated Dielectric
           Spacer

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      Authors: Takuya Kaji;Hiroyasu Sato;Qiang Chen;Shimpei Nagae;Akira Kumagai;Osamu Kagaya;
      Pages: 4843 - 4850
      Abstract: In this article, a leay wave antenna with dielectric superstrate (LWADS) on the perforated dielectric spacer is proposed. The LWADS has an asymmetric structure with a half-filled dielectric spacer and with a nonfilled spacer to make a quasi-cutoff region. The half-filled dielectric spacer is periodically perforated, and the beam direction of the leaky wave is controlled by changing the hole radius. In general, the unwanted radiation occurs in the broadside direction when the beam of the leaky wave is tilted at a large angle, and this unwanted radiation is avoided by providing these perforated dielectric spacers. The proposed design is validated by measurements at X-band, and it is shown that a high gain tilted beam pattern with peak gains of 14 dBi is obtained not only at $theta =20^{circ }$ and 40° but also at the wide-angle of $theta =60^{circ }$ . Since the effective permittivity can be controlled by the hole radius, an array of LWADS with different beam angles can be realized with the same height and a multibeam antenna with switched feeding can be realized.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Triple-Band Uni-Cavity Fabry–Perot Cavity Antenna With Hybrid
           Excitation Modes

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      Authors: Qiming Wang;Jiaran Qi;Ari Sihvola;
      Pages: 4851 - 4861
      Abstract: A novel methodology realizing multiband Fabry–Perot cavity antenna (FPCA) is proposed. Different from single transmission-mode (T-mode) or reflection-mode (R-mode) FPCA, the R- + T-mode FPCA employs hybrid excitation modes to the same FPC, reducing the requirement for multiband high-quality feed antennas. To verify this methodology, a triple-band FPCA integrated by two R-mode ones, operating at the middle and the high bands, and a T-mode one working at the low band is designed. A triband partially reflective surface (PRS) offering bidirectional asymmetric transmission for middle and high bands, and partial reflection for the low band, is proposed. Meanwhile, a triband artificial magnetic conductor (AMC) is designed to fulfill the in-phase bouncing condition in a low-profile uni-cavity for all bands. One intercavity feed and two external ones are utilized to complete the hybrid excitation of the FP cavity. Finally, a proof-of-concept prototype is fabricated showing −3-dB gain bandwidths of 7.0% ( $3.02-3.24$ GHz), 16.9% ( $5.38-6.37$ GHz), and 10.0% ( $10.31-11.40$ GHz). Beam-scanning ranges of ±35° and ±30° are also obtained for the middle and the high bands, respectively. The proposed methodology may readily realize an FPCA of even more frequency bands with limited aperture size and a low-profile resonant cavity.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Beamforming Network Design Utilizing Node Microstrip Architectures for
           Dual-Polarized Endfire Millimeter-Wave Antenna Arrays

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      Authors: Shiwen Tang;Yujie Zhang;Junhui Rao;Zixiang Han;Chi-Yuk Chiu;Ross Murch;
      Pages: 4862 - 4873
      Abstract: A node microstrip architecture is proposed for designing a compact Butler matrix (BM) that is integrated with a dual-polarized endfire antenna array. The node microstrip architecture can be used to form a variety of compact 2 × 2 port networks including, but not limited to, couplers and crossovers. By concatenating the 2 × 2 port networks together, a compact BM with any number of ports can be formed. Using the proposed method, a compact 4 × 4 port BM operating in the millimeter wave (mmWave) band is designed and integrated with a dual-polarized endfire antenna array. The size of the compact BM is $2.1lambda times 2lambda $ and the size of the whole dual-polarized endfire antenna array with BM is $2.6lambda times 4.8lambda $ , which is smaller than traditional structures. The measured radiation pattern of the dual-polarized antenna array can achieve beam scanning up to ±38° in the azimuth plane. The two beams in the dual-polarized endfire antenna array can also be independently steered. The optimized compact BM is potentially suitable for use in fifth-generation (5G) wireless communication handsets.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Wideband and High-Gain Circularly Polarized Antenna Array for
           Radio-Frequency Energy Harvesting Applications

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      Authors: Jifei Sang;Libo Qian;Minhua Li;Jian Wang;Zhangming Zhu;
      Pages: 4874 - 4887
      Abstract: A wideband millimeter-wave (mmWave) circularly polarized (CP) complementary antenna array is proposed herein for radio-frequency energy harvesting (RFEH) applications. The element is constructed of a CP magneto-electric (ME)-dipole antenna and innovatively introduces the complementary source technique to improve the CP radiation performance. The detailed analyses are provided to elaborate the operating principles of the element. Simulated results for the element reveal an impedance bandwidth of 25.7%, a 3-dB axial ratio (AR) bandwidth of 24.8%, and a gain of 8.7 ± 1.6 dBic over the spectrum. The element shows the stable radiation pattern and wide AR/impedance overlapping bandwidth (33.87–43.15 GHz) for RFEH applications covering the 35-, 37-, and 39-GHz bands. To enhance the gain for practical applications, the element is employed in the design, fabrication, and testing of a planar $4times $ 4 array fed by a full-corporate substrate-integrated waveguide (SIW) network. Measured results indicate that the array achieves an impedance bandwidth of 20.2%, a 3-dB AR bandwidth of 24.3%, and a 3-dB gain bandwidth of 22.8%. Thus, the proposed array features a low profile and excellent performance, which makes it a desirable candidate for mmWave RFEH applications.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Current Based Automated Design of Realizable Metasurface Antennas With
           Arbitrary Pattern Constraints

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      Authors: Marcello Zucchi;Francesco Vernì;Marco Righero;Giuseppe Vecchi;
      Pages: 4888 - 4902
      Abstract: We present a 3-D method to numerically design a realizable metasurface, which transforms a given incident field into a radiated field that satisfies mask-type (inequality) constraints. The method is based on an integral equation formulation, with local impedance boundary condition (IBC) approximation. The procedure yields the spatial distribution of the impedance, yet the process involves the synthesis of the equivalent current only. This current is constrained to correspond to a realizable surface impedance, i.e., passive, lossless, and with reactance values bounded by practical realizability limits. The current-based design avoids any solution to the forward problem, and the impedance is obtained from the synthesized current only at the end of the process. The procedure is gradient-based, with the gradient expressed in closed form. This allows handling large metasurfaces, with full spatial variability of the impedance in two dimensions. The method requires no a priori information, and all relevant operations in the iterative process can be evaluated with $boldsymbol { O}(N~log~{N})$ complexity. Application examples concentrate on the case of on-surface excitation and far-field (FF) pattern specifications; they show designs of circular and rectangular metasurface antennas of 20 wavelengths in size, with pencil- and shaped-beam patterns, and for both circular and linear polarizations.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Optimal Amplitude–Density Synthesis of Linear Aperiodic Arrays

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      Authors: Piero Angeletti;Giovanni Toso;
      Pages: 4903 - 4918
      Abstract: New deterministic procedures for the design of linear aperiodic arrays are described, which permit exploiting, in a combined way, both the positions and the excitation amplitudes of the array elements obtaining a pattern, which optimally fits, in terms of a weighted L2 norm, the pattern of a reference linear continuous aperture. The first numerical procedure is based on alternating optimization of positions and amplitudes by means of closed-form convex projectors. Sufficient conditions for the solution to be optimal are established. A second numerical procedure is based on a domino-like sequential determination of the unknowns, which can be iterated to convergence. In addition, analytical asymptotic expressions for the optimal interelement spacing and amplitude are derived by means of variational techniques. The optimal asymptotic interelement spacing is demonstrated to be proportional to the reference tapering to the power ( $- frac {2}{3}$ ), while the optimal asymptotic array amplitude is proportional to the reference tapering to the power ( $frac {1}{3}$ ). For aperiodic arrays with equiamplitude excitation, it is proven that the optimal interelement spacing is proportional to the reference tapering to the power (−1). Based on these asymptotic dependencies, closed-form analytical solutions are obtained for amplitudes and positions of the elements. Several numerical results confirm the effectiveness and accuracy of the new procedures.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Synthesis of Near-Field Arrays Based on Electromagnetic Inner Products

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      Authors: Francesco Lisi;Andrea Michel;Paolo Nepa;
      Pages: 4919 - 4931
      Abstract: Near-field (NF) antennas have been successfully adopted in several wireless applications. To exploit the high reconfigurability of array antennas, multiple synthesis techniques for arrays operating in the NF region have been proposed. Building upon previous works on eigenmode expansions of the radiated fields, two synthesis methods for the excitations of NF arrays based on the definition of an inner product on the electromagnetic fields are investigated: the “maximum norm” and “minimum error field norm” methods. The “maximum norm” method computes the array excitations that maximize either the active power flow through a target surface or the electric/magnetic energy stored in an assigned volume, depending on the adopted inner product. The performance of the maximum active power flow method is compared with one of the simpler conjugate phase methods. Furthermore, the limit solution achieved when the target surface reaches the far-field region is compared against the “maximum beam collection efficiency” method. The “minimum error field norm” method allows to synthesize a given target field. As an example, the latter method is used to find the optimal excitation of a plane wave generator with a spherical quiet zone. The effectiveness and performance of the discussed synthesis methods are validated through numerical simulations.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Broadband Low-Profile Dual-Circularly Polarized Reflect-Array Based on a
           Single-Layer Microstrip Patch for Ka-Band Application

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      Authors: Xi Wang Dai;Yu Hui Zhang;Weiliang Yu;Leilei Liu;Guo Qing Luo;
      Pages: 4932 - 4940
      Abstract: A broadband low-profile dual-circularly polarized (dual-CP) reflect-array (RA) cells covering both K- and Ka-bands is presented in this article. As an anisotropic impedance surface, the functional layer is designed based on a multi-resonant structure and printed on a substrate with a thickness of 0.762 mm. The circuit is composed of an elliptical ring, arc-shaped and rectangular metal microstrip lines. The air layer between the functional layer and the metal plate can effectively extend the cell bandwidth (BW), and the overall profile is 1.8 mm. The dynamic phase and Berry phase can be adjusted by changing the size of the arc-shaped microstrip lines and the rotation of the cells. The diffraction results show that the phase of left-handed (LH) circularly polarized (CP) and right-handed (RH) CP waves can be controlled independently and reflected by high purity with the cross-polarization BW of 64% (19.72 $sim $ 38.44 GHz). A dual-CP RA with 1013 cells is designed to realize reflect beams at $theta $ = −20° for LHCP wave and $theta $ = 15° for RHCP wave at 30 GHz. Furthermore, the 3 dB gain BW can cover the Ka-band and is expected to be used in wireless and satellite communication systems.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • SASA: Super-Resolution and Ambiguity-Free Sparse Array Geometry
           Optimization With Aperture Size Constraints for MIMO Radar

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      Authors: Mingsai Huan;Junli Liang;Yifan Wu;Yongkang Li;Wei Liu;
      Pages: 4941 - 4954
      Abstract: To improve the performance of multiple-input–multiple-output (MIMO) radar, various sparse arrays have been used. However, the angular resolution of existing nonuniform arrays optimized by either combinatorial algorithms or heuristic ones is limited by the Rayleigh criterion, which is strictly related to the aperture size. Based on the angular ambiguity function (AAF) analysis, two new models are established in this work for directly optimizing the sidelobe level (SLL) or the main lobe width (MLW) with the constraints of aperture size and element spacing. The aforementioned designs result in non-convex and nonlinear optimization problems, and solutions are derived via the alternating direction multiplier method (ADMM). Furthermore, considering a parametric tradeoff between SLL and MLW, a hybrid algorithm is proposed to search for the SLL-MLW Pareto front boundary. Finally, simulations are provided to demonstrate the high angular resolution and ambiguity-free properties of the optimized sparse arrays.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • An Integrated Dual-Band Dual-Circularly Polarized Shared-Aperture
           Transmit-Array Antenna for K-/Ka-Band Applications Enabled by Polarization
           Twisting Elements

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      Authors: Xuanfeng Tong;Zhi Hao Jiang;Yuan Li;Fan Wu;Jianjun Wu;Ronan Sauleau;Wei Hong;
      Pages: 4955 - 4966
      Abstract: An integrated dual-band dual-circularly polarized (dual-CP) transmit-array (TA) antenna operating at K- and Ka-bands is proposed. Antenna-filter-antenna (AFA) based polarization twisting TA cells possessing high cross-polarized and low copolarized linearly-polarized (LP) transmission characteristics are designed. These TA cells possess highly efficient circular-polarization transmission with flipped handedness without using any 180° phase shifting lines, thus bringing about benefits such as symmetrical structures, design simplification, and more consistent circularly polarized (CP) transmission magnitudes. In addition, the dual-band dual-CP transmissive beamforming characteristics are realized by arranging K- and Ka-band cells in the same aperture and employing a hybrid phase compensation strategy. For reducing the overall device profile, right-handed CP (RHCP) and left-handed CP (LHCP) planar arrays operating at K- and Ka-bands are fabricated as feeds for the TA. A dual-band dual-CP TA antenna with independently controllable beam directions is synthesized and experimentally demonstrated. The measured 2-dB gain and axial ratio (AR) bandwidths are 11.7% and 10.2% for K-band RHCP and LHCP beams, and the two CP beams own bandwidths of about 7.5% at Ka-band. The proposed dual-band dual-CP TA antenna can be a promising candidate for satellite communications and so on.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Efficient Synthesis of Concentric-Rings Plane Wave Generators

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      Authors: Daniele Pinchera;Marco Donald Migliore;
      Pages: 4967 - 4975
      Abstract: In this article, we present an efficient method for synthesizing sparse plane wave generators (PWG) based on concentric ring arrays. In particular, we introduce a novel circularly polarized ring source whose field on a near-field surface can be represented using only three scalar functions. Using this representation, we can simplify the synthesis, reducing substantially its computational complexity, which can be easily handled using an ordinary office PC. After using the ring sources to identify the position and excitation of the PWG elements, we can use discrete linearly polarized sources as feeds or use different kinds of radiators. Some numerical simulations validate the proposed approach, which can obtain planar and volumetric quiet zones (QZs) with good polarization purity.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Homogenization of Periodic Structures Using the Multimodal Transfer Matrix
           Method

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      Authors: Ana C. Escobar;Francisco Mesa;Oscar Quevedo-Teruel;Juan D. Baena;
      Pages: 4976 - 4989
      Abstract: This work presents a method for obtaining the constitutive parameters of periodic structures from the computation of their dispersion relation and average fields. The method uses the scattering parameters (S-parameters) of multiple Bloch modes of a single unit cell. The corresponding multimodal scattering matrix is obtained with a suitable general-purpose electromagnetic software. Further post-processing of this scattering matrix is then carried out, which allows for the computation of the dispersion relation of structures with realistic finite conductivity or made of lossy dielectrics, as well as the calculation of the attenuation constant and the retrieval of the impedance, permittivity, and permeability. The proposed method is applied to homogenize some systems of interest: an artificial electric plasma built with wires, a free-space matched left-handed metamaterial based on two laterally shifted split ring resonators, a high-permittivity artificial dielectric based on densely arranged square metal patches, and a $mu $ -near-zero metamaterial made of metallic cubes embedded in a dielectric. The retrieved material parameters are found to accurately describe the scattering of finite samples of the corresponding homogenized structures. This research is limited to orthorhombic unit cells smaller than half the free-space wavelength to avoid diffracted beams. Besides, since only one propagation direction is considered, only the transverse components of constitutive parameters are retrieved.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Multiple Scattering Model for Beam Synthesis With Reconfigurable
           Intelligent Surfaces

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      Authors: Tommi E. Rimpiläinen;Riku Jäntti;
      Pages: 4990 - 5000
      Abstract: This article presents a method of synthetic beamforming for reconfigurable intelligent surfaces (RIS). The method uses a $T$ -matrix-based multiple scattering model to compute the scattering from the RIS. We assume that the elements of the RIS are infinite circular cylinders. This allows us to make the model 2-D. Furthermore, we assume that the RIS elements satisfy the impedance boundary condition (IBC), the complex parameter of which adjusts the phase shift of the scattered field. We synthesize the beam both analytically and numerically. Both approaches rely on an approximation that assumes RIS elements that are small compared to the wavelength. We demonstrate the efficacy of the beam synthesis by applying it in a test case that features a linear array of RIS elements.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Collective-Coupling Enhanced Ultrabroadband Linear Polarization Conversion
           on Zigzag-Split Metasurfaces

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      Authors: Munan Yang;Feng Lan;Yaxin Zhang;Limei Qi;Guiju He;Yibo Pan;Tianyang Song;Luyang Wang;Pinaki Mazumder;Hongxin Zeng;Ziqiang Yang;
      Pages: 5001 - 5013
      Abstract: Polarization manipulation plays a pivotal role in integrated multifunctional devices. Various metasurface-based polarization converters successfully demonstrated high efficiency and broad bandwidth. However, new mechanisms to aggressively enhance performance are still in dire need. Here, theoretical and experimental evidence corroborates an efficient ultrawideband transmissive polarization converter based on a topological design method. The triple-layer meta-device consists of a layer of anisotropic zigzag-split resonator array amid two orthogonal wire-grating layers. By splitting double zigzag lines into compound 90° V-shaped resonators, the intraunit cross coupling extends to strong interunit cross coupling, giving birth to the multiresonance enhancement and significant bandwidth broadening. This polarization converter can efficiently convert linearly polarized incident waves into 90° cross-polarized transmitted waves, with a conversion efficiency above 80% over 3.98–22.71 GHz, reaching a fractional bandwidth of 140.4%. The proposed meta-device enables strong cross coupling in mutual transition from intraunit to interunit. From a physical viewpoint, the novel mechanism is elucidated by the surface current and electric field distributions upon constructive interferences stemming from V-shape-resonator combinations and the Fabry–Pérot-like cavity effect. With both spectrum and function extensions, the proposed polarization conversion strategy finds essential applications in polarization-related systematic scenarios, such as 6G communication, radar imaging, anti-interference, and chiral sensing.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Hybrid SRR-Based Stacked Metamaterial for Miniaturized Dual-Band Wireless
           Power Transfer System

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      Authors: Xin Jiang;Ramesh K. Pokharel;Adel Barakat;Kuniaki Yoshitomi;
      Pages: 5014 - 5025
      Abstract: A novel stacked wideband metamaterial is proposed for a robust and compact dual-band wireless power transfer (WPT) system. The proposed metamaterial employs split-ring resonator (SRR) unit cells loaded by nonuniform capacitors. First, two types of unit cells that exhibit two resonance frequencies are analyzed. The results show that it can only improve the coupling between the transmitter (Tx) and the receiver (Rx) at the single band. Then, each unit cell is sandwiched with each other, and a hybrid unit cell that indicates three resonance frequencies is finally proposed. The hybrid SRR exhibits near-zero permeability within the wide frequency range of interest. Therefore, the proposed metamaterial is effective at both bands simultaneously. The system was fabricated and tested, including a compact dual-band WPT system. The size of the Tx (Rx) and the metamaterial is $15times15$ and $20times20$ mm, respectively. The measured figures of merit (FOM) are 0.92 at 390 MHz and 0.85 at 770 MHz at a power transfer distance of 20 mm, which is a significant improvement over recently proposed dual-band WPT systems with metamaterials.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Waveguide Antenna Topologies for Distributed High-Frequency Near-Field
           Communication and Localization

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      Authors: Artem Voronov;Oleksiy Sydoruk;Richard R. A. Syms;
      Pages: 5026 - 5035
      Abstract: High-frequency (HF) near-field communication (NFC) is an inherently short-range technology. However, the total capture volume can be increased with traveling-wave antennas. Here, we report on the analysis, design, and measurements of flexible waveguide antennas and discuss their performance for NFC and localization. The antennas comprise sections of coaxial transmission lines loaded periodically with field-generating inductive networks. Several topologies were compared to each other theoretically, and the best-performing candidate was selected to fabricate antennas between 5 and 48 m long, each containing 15 read nodes. Waveguiding properties of the antennas were measured and agreement with the theory was demonstrated. Afterward, each antenna was integrated with a custom NFC reader and shown to be capable of communication with and localization of commercial off-the-shelf transponders compliant with ISO/IEC 14443 Type A protocol. The transverse detection range was 10 cm with 1 W input RF power. Both 1-D and quasi-2-D configurations were tested. The proposed antennas are flexible, scalable, have low loss, and could be used for NFC, identification, and tracking of distributed and mobile tags.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Full-Range Amplitude–Phase Metacells for Sidelobe Suppression of
           Metalens Antenna Using Prior-Knowledge-Guided Deep- Learning -Enabled
           Synthesis

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      Authors: Peiqin Liu;Zhi Ning Chen;
      Pages: 5036 - 5045
      Abstract: A prior-knowledge-guided deep-learning-enabled (PK-DL) synthesis method is proposed to design the metacells with the full-range amplitude and phase control for suppressing the sidelobe levels (SLLs) of a metalens antenna. The PK-DL synthesis method is based on a conditional deep convolutional generative adversarial network (cDCGAN). First, the metacells are pixelated to offer the higher degrees of design freedom and expand their transmission responses to full 2-D coverage of amplitude and phase responses so that a full-range metacell dataset is built up to simultaneously control the amplitude and phase of a single metacell. Conventionally, by optimizing the dimensions of predefined patterns of a metacell, only the phase response of a single metacell is achieved with a specific amplitude response, and vice versa. The metalens design based on the synthesized metacells has much higher degrees of freedom so that the metalens antenna has the potential to break the ceiling of performance and to realize more functions than existing metalens designs. As examples, two types of single-lens metalens antennas are designed for sidelobe suppression using the proposed metacell dataset. The first metalens is excited by a dipole antenna with an omnidirectional radiation pattern to demonstrate the simultaneous control of amplitude and phase responses using the synthesized metacells. The second metalens fed by a standard horn antenna is designed to suppress the SLLs in both the E- and H-planes. The horn-fed square metalens has an aperture of $13.2times 13.2,,lambda _{0}$ at 12 GHz. Measurement shows that the proposed metalens antenna realizes the gain of 26.9 dBi at 12 GHz and the first SLLs in the E- and H-planes are −33.2 and −30.9 dB, respectively. The proposed synthesis method greatly expands the boundary of amplitude and phase responses of a single metacell so that -he metacell dataset offers much higher degrees of freedom for not only metalenses but also other metasurfaces.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Filtenna-Filter-Filtenna-Based FSS With Simultaneous Wide Passband and
           Wide Out-of-Band Rejection Using Multiple-Mode Resonators

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      Authors: Huawei Lin;Sai-Wai Wong;Kam-Weng Tam;Yin Li;Kong Ngai;Chi-Hou Chio;Yejun He;
      Pages: 5046 - 5056
      Abstract: A novel filtenna-filter-filtenna (FA-F-FA)-based frequency-selective surface (FSS) technique is proposed using multiple-mode resonators (MMRs). Based on this method, a bandpass FSS with simultaneous wide passband and wide out-of-band rejection is validated. The MMR unit cell consists of two back-to-back magnetoelectric (ME)-dipole antennas and a filter-embedded GND plane. Four modes are analyzed and used to acquire a wide passband of the FSS. At the same time, wide out-of-band rejections in both lower and upper bands are controlled by the filter-embedded GND plane with four rotationally symmetric quarter-wavelength transmission lines (QWTLs). Moreover, the GND plane plays a crucial role in the impedance matching of the proposed FSS. As a result, four transmission poles (TPs) and three transmission zeros (TZs) of the proposed FSS can be obtained, leading to a fourth-order filtering response and wide out-of-band rejection. An equivalent circuit model, current distributions, and electric field distributions are introduced to illustrate the working mechanism of the FSS. Finally, the proposed FA-F-FA-based FSS with a 50.2% 3-dB fractional bandwidth (FBW $_{mathrm {3 dB}}$ ) in the passband and 53.5% and 119.2% of the 20-dB fractional bandwidth (FBW $_{mathrm {20 dB}}$ ), respectively, in the lower and upper rejection bands is achieved. The S-parameters are stable under an oblique incident angle of 50°. The measured and simulated results are in good agreement. In addition, the proposed FSS has the advantages of low profile, assembly free, and dual-polarization application, which verify the versatility of the FA-F-FA-based MMR FSS.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Low-Scattering Phased Arrays With Reconfigurable Scattering Patterns Based
           on Independent Control of Radiation and Scattering

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      Authors: Zhechen Zhang;Shiwen Yang;Feng Yang;Yikai Chen;Shi-Wei Qu;Jun Hu;
      Pages: 5057 - 5066
      Abstract: A novel approach for the independent manipulation of the in- band scattering and radiation patterns of phased arrays with high radiation efficiency is proposed. The in- band scattering and radiation mechanism of an array element is analyzed first. It is found that the antenna input impedance may lead to different effects on the antenna scattering and radiation patterns. Taking advantage of this difference, an array element incorporated with a biased p-i-n diode is designed, which has two scattering states with 180° phase differences but a stable radiation state. By controlling the biasing state of the p-i-n diode connected to each element, the scattering pattern of the proposed array can be manipulated dynamically. Meanwhile, the stable radiation pattern of the designed element ensures that the proposed phased array can dynamically radiate a beam scanning to a given direction with high efficiency during the manipulation of scattering patterns. The final designed linear array with p-i-n diodes is able to operate at 2.6–3.4 GHz with a radiation beam scanning up to ±45°. Moreover, the reconfigurable scattering beams of the proposed array can point to arbitrary angles within ±60°, thus the in- band scattering is significantly reduced in a broad bandwidth. To validate this design, a prototype array is fabricated and measured. Measured results are in good agreement with the simulated results.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Scalable 3-D-Printable Antenna Array With Liquid Cooling for 28 GHz

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      Authors: Jaakko Haarla;Juha Ala-Laurinaho;Ville Viikari;
      Pages: 5067 - 5078
      Abstract: This article presents a scalable and compact 3-D-printed Vivaldi antenna array with liquid cooling for the frequency band from 24.0 to 29.5 GHz. The proposed design consists of an $8 times 8$ antenna array with commercial beam-forming integrated circuits (ICs) on the antenna side of the PCB for efficient PCB area utilization that enables a high integration level. Scalable liquid cooling is integrated into the 3-D-printed antenna array. The measured temperature with water cooling during operation remains below $50 ^{circ} text{C}$ . The simulated total active reflection coefficient (TARC) of the unit cell is lower than −9.6 dB for beam steering angles up to 57° from the broadside. The effective isotropic radiated power (EIRP) of the prototypes is up to 59.7 dBm.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Can Perfectly Electric Conducting Obstacles Modify the Permeability of
           Metamaterial' An Investigation Using Lorentz, Floquet, and Full-Wave
           Models

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      Authors: Arun K. Bhattacharyya;
      Pages: 5079 - 5088
      Abstract: The Lorentz model shows that the inclusion of perfectly electric conducting (PEC) obstacles in a host medium introduces both electric and magnetic polarizabilities that modify the permittivity and permeability tensors of the composite medium. In contrast, the Floquet eigenmodal analysis shows that the PEC obstacles, while modifying the permittivity tensor, have no effect on the permeability tensor. Interestingly, numerical results obtained from full-wave analyses of metamaterial slabs support the Floquet model. The source for the inaccuracy in the Lorentz model is critically examined. Characteristic features of metamaterials made with nonresonant and resonant types of obstacles are investigated, and the numerical results obtained from four independent models are compared and discussed.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Support Vector Regression Models of Reflectarray Unit Cell in a
           Geometrical 4-D Parallelotope Domain Around a Rectangle of Stability

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      Authors: Daniel R. Prado;Jesús Alberto López-Fernández;Manuel Arrebola;
      Pages: 5089 - 5099
      Abstract: In this work, surrogate models based on support vector regression (SVR) of a multiresonant unit cell in a geometrical 4-D parallelotope domain are trained and used in a reflectarray antenna design. The multiple sharp resonances of the unit cell prevent a suitable training process in the whole orthotope defined by the available degrees of freedom (DoFs). Thus, a strategy to improve the training process and obtain highly accurate models is devised. It consists in defining a parallelotope around a rectangle of stability, which is in turn defined at a lower dimensionality. The SVR models with four geometrical DoF obtained in this parallelotope are shown to provide highly accurate results for the design of a large contoured-beam reflectarray for space applications. The direct optimization with the surrogate models allows to improve the cross-polarization performance by several decibels while considerably increasing computational performance. Furthermore, compared to lower dimensionality models, the 4-D models offer better results when applied to wideband and dual-band reflectarray direct optimization.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Solution to the Dilemma for FSS Inverse Design Using Generative Models

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      Authors: Zheming Gu;Da Li;Yunlong Wu;Yudi Fan;Chengting Yu;Hongsheng Chen;Er-Ping Li;
      Pages: 5100 - 5109
      Abstract: Recently, artificial neural networks (ANNs) show a great potential in frequency-selective surface (FSS) inverse design. However, it is inevitable to encounter the problem of nonunique mapping between inputs and outputs, which cannot be easily solved by the traditional ANNs framework. We analyze this existing dilemma from the perspective of information loss caused by data dimensionality reduction and propose deploying generative models as a solution for the first time. Specifically, two approaches with a novel model based on conditional generative adversarial network (cGAN) are presented to achieve inverse design from the given indexes to FSS physical dimensions. By applying the proposed method, we can immediately obtain the FSS design that meets the industrial demands without complex neural network processing or repeated iterations. Moreover, the proposed method is validated in closed-loop simulations and corresponding experiments, which also paves the way for designing complex FSS structures with the desired electromagnetic responses using deep neural networks.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Microwave Imaging of 3-D Dielectric–Magnetic Penetrable Objects Based on
           Integral Equation Method

    • Free pre-print version: Loading...

      Authors: Yuan He;Li Zhang;Mei Song Tong;
      Pages: 5110 - 5120
      Abstract: Some objects such as mineral substances may be both dielectric and magnetic and their high-resolution inner imaging is very desirable when detecting and analyzing their ingredients. An integral equation method is developed for reconstructing or imaging such objects using microwave illumination. Since the objects are both dielectric and magnetic, full volume integral equations (VIEs) are needed to describe the problem. The objects can be reconstructed by alternatively solving the forward scattering VIEs (FSVIEs) and the inverse scattering VIEs (ISVIEs) under the Born iterative method (BIM) or distorted BIM (DBIM). The Nyström method is used to solve the FSVIEs while a Gauss–Newton minimization method (GNMM) with a multiplicative regularization scheme (MRS) is used to solve the ISVIE. The Nyström method is more suitable for solving the FSVIEs of inverse problems because it is a point-matching method. To accelerate the solution, the multilevel fast multipole algorithm (MLFMA) is incorporated with the Nyström method which is new for solving inverse problems. Also, using the MRS-based GNMM to solve the ISVIEs can facilitate the selection of regularization parameter and reduce the requirements on measured data. Numerical examples are provided to demonstrate the approach and good results have been achieved.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Unified Formulation of Leapfrog Complying Divergence Implicit FDTD Method
           for Lossy Media

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      Authors: Shuo Liu;Eng Leong Tan;Lamei Zhang;Bin Zou;
      Pages: 5121 - 5132
      Abstract: The leapfrog alternating direction implicit finite-difference time-domain (ADI-FDTD) method for lossy media has been found to suffer from the nonphysical field leakage problem in the non-penetrable structures, which gives rise to inaccuracies in modeling lossy media during scattering analyses. To address such problem, in this article, we propose a unified formulation of leapfrog complying divergence implicit (CDI)-finite-difference time-domain (FDTD) method for lossy media without field leakage problem. Several different lossy schemes to incorporate the conductivity terms of lossy media, including exponential time differencing (ETD), averaging, and forward–forward schemes, are integrated into a unified formulation. The proposed leapfrog CDI-FDTD method not only resolves the problem of field leakage but also has complying divergence. Moreover, since the implicit update procedures in the proposed formulation are in the fundamental form with matrix-operator-free right-hand sides (RHS), the floating-point operations (flops) are fewer than that of the conventional leapfrog ADI-FDTD formulation for lossy media. Numerical results are given to demonstrate the advantages of the proposed method over the leapfrog ADI-FDTD method in accuracy, efficiency, complying divergence, and resolving the field leakage problem for lossy media.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Domain-Decomposition-Based Surface Integral Equation Simulator for
           Characterizing EM Wave Propagation in Mine Environments

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      Authors: Weitian Sheng;Abdulkadir C. Yucel;Yang Liu;Han Guo;Eric Michielssen;
      Pages: 5133 - 5144
      Abstract: A domain-decomposition (DD)-based surface integral equation (SIE) technique for simulating electromagnetic (EM) wave propagation in large and realistic mine environments is proposed. After partitioning the mine into subdomains, the simulator characterizes EM wave propagation in each subdomain using a butterfly-based direct solver in conjunction with a fast multipole method (FMM)–fast Fourier transform (FFT) iterative scheme. Next, it constructs and solves a composite system characterizing inter-domain interactions. The simulator requires fewer CPU and memory resources than conventional SIE simulators to analyze EM wave propagation in electrically large mine environments. When applied to mines composed of a small set of identical “building blocks,” the simulator’s computational and memory requirements scale logarithmically as opposed to quasi-linearly with mine size. When used in closed-loop uncertainty quantification or wireless node placement studies, the simulator realizes additional computational savings by recycling many computations performed offline. Numerical results demonstrate the simulator’s accuracy and applicability to mine tunnels and galleries with arbitrary cross sections, rough walls, and debris from a partial cave-in.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • On the Surface Plasmonic Waves Excited by a Dipole Above Anisotropic and
           Spatially Dispersive Two-Dimensional Surfaces of Infinite Extent in
           Planarly Layered Media

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      Authors: Minyu Gu;Krzysztof A. Michalski;
      Pages: 5145 - 5157
      Abstract: The surface plasmonic waves (SPWs) excited by a vertical- or horizontal-oriented Hertzian dipole above anisotropic and spatially dispersive 2-D surfaces of infinite extent embedded in planarly layered uniaxial media are investigated using the dyadic Green function approach. The spectral-domain transmission line analogy Green function formulation and isofrequency-contour equations are derived. The methods to accurately and efficiently evaluate the 2-D Fourier integral arising from the spatial-domain Green function computation are also developed. To resolve the numerical inefficiency due to the highly oscillatory integrand and singularities of SPWs that possess large wavenumber, the methods of extrapolating the real-axis integration combined with singularity subtraction are proposed and found to be applicable to a wide range of observation distances. As an application example of the proposed formulation, we compute the scattered fields of a vertical dipole above the graphene biased by drift current, which exhibits significant spatial dispersion. It is shown that the light–matter interaction of graphene plasmons can be significantly reinforced when placed above uniaxially anisotropic epsilon-near-zero substrates. The proposed formulation may provide the methodology for the computational analysis of 2-D materials and SPWs.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Reduced-Order PCE-Based Time-Domain Method for Large Uncertainties

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      Authors: Kiran Ravindran;Kalarickaparambil Joseph Vinoy;
      Pages: 5158 - 5165
      Abstract: Evaluation of uncertainty in field values at a defibrillator probe embedded inside human heart muscles helps in improving the EMI/EMC design of the implants and setting the right thresholds for its safe operation in an environment with electromagnetic (EM) interference. Large variations in EM properties such as dielectric constant and conductivity are expected in such problems. In this article, a 3-D reduced stochastic radial point interpolation method (R-SRPIM) is developed for uncertainty quantification (UQ) in bioelectromagnetics. Derivatives of field quantities in Maxwell’s equations are obtained using the radial basis function, and stochasticity in the EM properties within the model space is incorporated into this formulation. The number of terms in the polynomial chaos expansion (PCE) and hence the computational complexity increases with large variations. To make the resulting formulation computationally viable, the sparsity of the stochastic matrix is enforced by utilizing the linearization property of the product of three Hermite polynomials and using singular value decomposition (SVD). The accuracy of the proposed approach is validated using the Kolmogorov–Smirnov (KS) test, with Monte Carlo (MC) simulations and COMSOL multiphysics.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Numerical Mode Matching (NMM) Method for Optical Fibers With Kerr
           Nonlinearity

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      Authors: Xue Liang Wu;Junwen Dai;Jie Liu;Jin-Hui Chen;Qing Huo Liu;
      Pages: 5166 - 5177
      Abstract: Recently, the reshaping of the transverse light field profile in nonlinear multimode fibers (MMFs) has attracted great attention. However, the electromagnetic (EM) fields in such nonlinear media cannot be easily and accurately calculated by using the traditional computational EM methods due to the nonlinearity of Kerr optical materials in graded-index (GRIN) MMFs. The iterative division method based on the 2.5-D spectral numerical mode matching (SNMM) method is developed to address this problem. The SNMM method is a semianalytical method, which can effectively reduce the computational costs to obtain highly accurate solutions. Starting from the numerical results of SNMM, the iterative division method solves the EM fields of the linear-to-nonlinear transition process together iteratively. In this work, several improvements are proposed to extend the SNMM for Kerr optical nonlinear MMFs. The governing equations with anisotropic permittivity with Kerr optical nonlinear media are established in the cylindrical coordinate system. The absorbing boundary condition (ABC) is introduced to replace the perfectly matched layer (PML) so that the eigenmodes of a waveguide can be obtained accurately. Numerical results show the validity, accuracy, and advantages of the proposed method in simulated MMFs.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Numerically Stable Calculations of the Spherically Layered Media Theory

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      Authors: Hao Yu Yuan;Wei Zhu;Bo O. Zhu;
      Pages: 5178 - 5188
      Abstract: The electromagnetic (EM) scattering of a layered sphere is a canonical problem. Mie theory is suitable for plane wave incidence cases, whereas spherically layered media theory (SLMT) can deal with arbitrary incident waves. Both Mie theory and SLMT suffer from numerical instabilities due to the involved spherical Bessel functions when the order is large, the argument is small, or the medium is lossy. The logarithmic derivative method had been proposed to solve this numerical issue with Mie theory successfully, while the numerical issue with SLMT has not been solved fully so far. Computations of reflection and transmission coefficients are the key part of SLMT. In this article, we first define the renormalized reflection and transmission coefficients, which enjoy the feature of having an ordinary level of magnitude. Then, borrowing the idea of the logarithmic derivative method, the expressions for the renormalized canonical reflection and transmission coefficients as well as other terms in the theory are rearranged. Recursive formulas for the product or division of Bessel functions with some common combinations of order and argument are derived. Numerical tests show that the proposed approach, validated by the full wave numerical method, is more stable than the conventional formulation.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Short-Term Forecast Method of Maximum Usable Frequency for HF
           Communication

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      Authors: Jian Wang;Yafei Shi;Cheng Yang;Zhigang Zhang;Lin Zhao;
      Pages: 5189 - 5198
      Abstract: To further improve the quantitative forecasting ability of high-frequency (HF) communication frequency, we propose a maximum usable frequency (MUF) adaptive forecasting method. This method has four new features: 1) the Volterra filter is introduced to this method, which is easy to implement due to the simple structure; 2) this method can forecast M(3000)F2 based on past measurements without using any previous or forecast data of geomagnetic and solar activity parameters; 3) the spatial characteristics of the M(3000)F2 can be obtained by the improved reconstruction method based on geomagnetic coordinates (GMCs); and 4) the high prediction accuracy can be obtained by the training dataset on the 27th day (one solar rotation period). Through the statistical analysis of the measurements and predictions, the results show that the forecast values are in good agreement consistent with the measurement during the geomagnetic quiet or the disturbance periods. This method is proven to have good adaptability and usability and has a further performance improvement compared with International Telecommunication Union (ITU) and long-term forecast models. And the root-mean-square error (RMSE) of MUF forecasts decreased by 1.9 and 0.9 MHz on average, and the relative RMSE decreased by 12.6% and 2.9% on average.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Antenna Array Analysis by Iterative DGFM-Based Local Solutions

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      Authors: André S. Conradie;Matthews Chose;Pierre I. Cilliers;Matthys M. Botha;
      Pages: 5199 - 5211
      Abstract: The method of moments (MoM) is well suited to the electromagnetic analysis of antenna arrays, but solution cost grows rapidly with array size. This article concerns efficient MoM analysis of large antenna arrays with identical disjoint elements in arbitrary layouts. The domain Green’s function method (DGFM) is a domain decomposition method (DDM) for such arrays. Its unique benefit is that only local problems are solved to obtain an approximate global solution. Its main drawback is uncontrolled, problem-dependent solution errors. An improved scheme denoted iterative radius-based DGFM (IRB-DGFM) is formulated, in standard and residual-driven (RD) versions. Accuracy is improved by introducing local MoM domains, and solution error control is achieved via an iterative scheme, to obtain the true MoM solution to user-specified tolerance. Various computational cost reduction methods are proposed for the new formulations. Results show that the RD-IRB-DGFM is superior, yielding rapid convergence for diverse arrays. The methods are ideally suited to parallelization.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A 3-D Hybrid Maxwell’s Equations Finite-Difference Time-Domain
           (ME-FDTD)/Wave Equation Finite-Element Time-Domain (WE-FETD) Method

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      Authors: Jiaxuan Wang;Qiang Ren;
      Pages: 5212 - 5220
      Abstract: In this article, a 3-D hybrid Maxwell’s equations finite-difference time-domain (ME-FDTD)/wave equation-based finite-element time-domain (WE-FETD) method is proposed. This method retains the nonconformal mesh and the implicit–explicit time integration scheme. The WE-FETD region is based on the wave equation rather than Maxwell’s curl equations. This method needs to store all the electric fields in the entire region and only the magnetic fields on the interface, which can prominently reduce degrees of freedom (DoFs) and save calculation time. The ME-FDTD region follows Yee’s scheme. A Maxwell’s equations spectral element time-domain (ME-SETD) region and a virtual region are used to combine the ME-FDTD and WE-FETD regions. Consequently, a WE-FETD/ME-SETD/Virtual/ME-FDTD framework is formed. Hybrid Newmark-beta (NB) and Crank–Nicolson (CN) time stepping are employed for implicit WE-FETD and ME-SETD regions. The leapfrog (LF) time integration is used for the explicit virtual and FDTD regions. At the interface, it employs upwind flux in the discontinuous Galerkin (DG) method to couple neighboring regions. Numerical examples are included to demonstrate the accuracy of the proposed method. Several cases exhibit the improved efficiency compared with the hybrid FDTD/FETD method only based on Maxwell’s equations and the pure FETD method.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Multifrequency Wireless Channel Measurements and Characterization in Large
           Indoor Office Environments

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      Authors: Li Zhang;Cheng-Xiang Wang;Zihao Zhou;Xinyue Chen;Jie Huang;Chun Pan;El-Hadi M. Aggoune;Yang Miao;
      Pages: 5221 - 5234
      Abstract: This article performs extensive channel measurements and characteristics analysis to investigate large-scale fading (LSF) and small-scale fading (SSF) of wireless local area network (WLAN) channels in large indoor office environments. Multifrequency single-input–single-output (SISO) channel measurements are conducted at 3, 5.5, and 6.5 GHz under the same conditions to explore the frequency dependence of LSF, delay spread (DS), and $K$ -factor (KF). Then, SISO channel measurements with different half-power beamwidths (HPBWs) of antennas are performed at 5.5 GHz in access point (AP) to user equipment (UE) and AP-to-AP scenarios. The effects of antenna HPBW on LSF, DS, and KF are investigated, thereby inspiring the AP deployment in high-density (HD) scenarios. Finally, $32 times 64$ multiple-input–multiple-output (MIMO) channel measurements at 5.5 GHz are conducted to study the SSF of the time nonstationarity and multilink correlation. The time nonstationarity, including the parameters’ drifting and cluster evolution caused by the movement of the UE, is verified by the measurement results. Multilink correlations are illustrated from the perspectives of the angular power spectral density (APSD) and correlation matrix collinearity (CMC). The results show that the distance between users and separation angle can affect the multilink correlation.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • UTD-Based Ray-Tracing MIMO Channel Modeling for the Next-Generation
           Communications Within Underground Tunnels

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      Authors: Mohamad Ghaddar;José-María Molina-García-Pardo;Ismail Ben Mabrouk;Martine Lienard;Pierre Degauque;
      Pages: 5235 - 5245
      Abstract: Limited work has previously been conducted into deterministic modeling of the fifth generation (5G) millimeter (mm)-wave wireless communications within geometrically nonuniform tunnels. This study predicts and analyzes broadband multiple–input multiple–output (MIMO) propagation in underground mine tunnels for 5G communications and beyond. At extremely short wavelengths, each rugged and uneven surface of the tunnel is modeled as a group of diffracting rectangular prism wedges. A deterministic ray-tracing (RT) MIMO model is developed based on the Uniform Theory of Diffraction (UTD). All predicted MIMO subchannels have been successfully fitted with the experimental measurements. MIMO multipath fading of underground tunnels is found to be lognormally distributed and strongly depends on the tunnel’s size and shape.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Wideband Linear-to-Multi-Polarization Converter Based on Active
           Metasurface

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      Authors: Hongcheng Zhou;Xiaoran Yu;Ping Wang;Yu Wang;Zhongming Yan;
      Pages: 5246 - 5255
      Abstract: This article proposes a transmission-type linear-to-multi-polarization converter based on cascading four-layer metasurface integrated with p-i-n diodes. By controlling the states of the p-i-n diodes, the polarization maintaining (PM) which means transmission without conversion, linear to linear (LTL), linear to right-hand circular polarization (LTRCP), linear to left-hand circular polarization (LTLCP) conversions can be realized. When the PM is realized, the incident wave will pass through the polarizer with low loss over wideband, the isolation is higher than 30 dB. When the linear-to-circular polarization (LTCP) conversion is realized, the incident linearly polarized (LP) wave can be converted to a left-hand circularly polarized (LCP) or right-hand circularly polarized (RCP) wave with a relative bandwidth over 40%. When the LTL polarization conversion is realized, the polarization conversion ratio (PCR) is greater than 0.9 from 2.58 to 3.89 GHz. The overlapping bandwidth of the four operating states is 36%. The detailed design process and equivalent circuit of the proposed polarizer are analyzed in this article. A sample consisting of $10times10$ elements is fabricated. The measured and simulated results are in good agreement. To the authors’ best knowledge, this is the first reported reconfigurable polarizer capable of PM, LTLCP, LTRCP, and LTL polarization conversions within wideband. The proposed device can play an important role in polarization diversity and RF-integrated aperture of wideband channel multiplexing technology.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Multimode OAM Convergent Transmission With Co-Divergent Angle Tailored by
           Airy Wavefront

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      Authors: Yufei Zhao;Ziyang Wang;Yilong Lu;Yong Liang Guan;
      Pages: 5256 - 5265
      Abstract: Wireless backhaul offers a more cost-effective, time-efficient, and flexible solution than wired backhaul to connect the edge-computing cells with the core network. As the amount of transmitted data increases, the low-rank characteristic of the line-of-sight (LoS) channel severely limits the growth of channel capacity in the point-to-point backhaul transmission scenario. Orbital angular momentum (OAM), also known as vortex beam, is considered as a potentially effective solution for high-capacity LoS wireless transmission. However, due to the shortcomings of its energy divergence and the specificity of multimode divergence angles, OAM beams have been difficult to apply in practical communication systems for a long time. In this work, a novel multimode convergent transmission with a co-scale reception scheme is proposed. OAM beams of different modes can be transmitted with the same beam divergent angle, while the wavefronts are tailored by the ring-shaped Airy compensation lens during propagation, so that the energy will converge to the same spatial area for receiving. Based on this scheme, not only is the signal-to-noise ratio (SNR) greatly improved but it is also possible to simultaneously receive and demodulate OAM channels multiplexed with different modes in a limited space area. Through prototype experiments, we demonstrated that three kinds of OAM modes are tunable, and different channels can be separated simultaneously with receiving power increasing. The measurement isolations between channels are over 11 dB, which ensures a reliable 16-QAM (quadrature amplitude modulation) multiplexing wireless transmission demo system. This work may explore the potential applications of OAM-based multimode convergent transmission in LoS wireless communications.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Wigner–Smith Time Delay Matrix for Electromagnetics: Systems With
           Material Dispersion and Losses

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      Authors: Yiqian Mao;Utkarsh R. Patel;Eric Michielssen;
      Pages: 5266 - 5275
      Abstract: The Wigner–Smith (WS) time delay matrix relates a system’s scattering matrix to its frequency derivative and gives rise to the so-called WS modes that experience well-defined group delays when interacting with the system. For systems composed of nondispersive and lossless materials, the WS time delay matrix previously was shown to consist of volume integrals of energy-like densities plus correction terms that account for the guiding, scattering, or radiating characteristics of the system. This study extends the use of the WS time delay matrix to systems composed of dispersive and lossy materials. Specifically, it shows that such systems’ WS time delay matrix can be expressed by augmenting the previously derived expressions with terms that account for the dispersive and lossy nature of the system, followed by a transformation that disentangles effects of losses from time delays. Analytical and numerical examples demonstrate the new formulation once again allows for the construction of frequency stable WS modes that experience well-defined group delays upon interacting with a system.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Simple Link-Budget Estimation Formulas for Channels Including Anomalous
           Reflectors

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      Authors: Sergei Kosulnikov;Francisco S. Cuesta;Xuchen Wang;Sergei A. Tretyakov;
      Pages: 5276 - 5288
      Abstract: Reconfigurable intelligent surfaces (RISs) are a promising tool for the optimization of propagation channels for advanced wireless communication systems. These tools are especially relevant for high-frequency (millimeter-band) links where directive antennas are used. RIS panels act as high-gain passive repeaters, whose reflected waves interfere with the waves reflected from the illuminated spots at supporting walls, creating a complex field pattern in the far zone. In this work, we consider a particular scenario of RISs for anomalous reflection and develop a simple link-budget model for nonline-of-sight (NLOS) channels via reflections from finite-size metasurfaces (MSs) designed as anomalous reflectors or splitters. The developed model takes into account diffraction at the RIS panel edges as well as interference with reflections from supporting structures. We take into account realistic losses and confirm the validity of results by numerical simulations.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Reconfigurable Over-the-Air Chamber for Testing Multi-Antenna Wireless
           Devices

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      Authors: Matthew D. Arnold;Michael A. Jensen;Rashid Mehmood;
      Pages: 5289 - 5298
      Abstract: The reconfigurable over-the-air (OTA) chamber (ROTAC) is a reverberation chamber with antennas positioned along the chamber walls. By controlling the signals driving a small number of these antennas and tunable impedances terminating the ports of the remaining antennas, the ROTAC offers dynamical control of the field incident on a mobile device during OTA testing. This article uses finite-difference time-domain electromagnetic simulations and measurements from a ROTAC prototype in combination with a network model to characterize the fields incident on the device as a function of the excitations and terminations. A gradient search optimization is formulated to determine the excitations and terminations required to approximate specified field characteristics in the chamber test zone, including multipath direction of arrival, signal correlation, and fading statistics. The article further explores the relationship between the field spatial sampling within the test zone and the ability to synthesize a field with the specified characteristics.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Fading of Wideband Signals Due to Propagation Through Equatorial Plasma
           Bubbles and Diversity Mitigation Effects

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      Authors: Emanoel P. O. Costa;Chaosong Huang;Ronald G. Caton;Patrick A. Roddy;
      Pages: 5299 - 5309
      Abstract: Equatorial Plasma Bubbles (EPBs) and their ionospheric density irregularities exhibit structures with scale sizes that can vary from several hundred kilometers to tens of meters. These random irregularities degrade both the performance and the availability of space-based communication and navigation systems in different ways. As examples of effects to be analyzed, wideband Ultra High Frequency (UHF) (360–380 MHz) transmissions received by Ascension Island (7.93 °S, 14.25 °W) monitors during an observational campaign in October 2016 displayed flat-fading and frequency-selective fading conditions. In this report, the ionospheric structures that are responsible for the harmful observed behavior (flat and frequency-selective fading) will initially be identified through the application of a discrete version of the single phase-screen formulation to low- and high-resolution in situ ion density data recorded by the Planar Langmuir Probe (PLP) onboard the Communications/Navigation Outage Forecasting System (C/NOFS) satellite. Next, the resulting hypothesis will be confirmed by the application of the continuous version of the same formulation to single-scale irregularities with different scale sizes. Finally, mitigation effects from space and frequency diversity on the observed behavior will be discussed with basis on the application of the initial formulation to the high-resolution C/NOFS PLP data.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Single-Cut Scattered Field Transformation Applicable for Differences in
           the Radar Ranges of Transmitter and Receiver

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      Authors: Yoshihiko Akamine;Takashi Tomura;Jiro Hirokawa;
      Pages: 5310 - 5321
      Abstract: This article proposes a new single-cut scattered field transformation method. The method extends the existing radiation reflector model to the case where the measurement distances from a target under test to a transmitter (TX) and a receiver (RX) are different. The method is applied to bistatic measurements using the monostatic to bistatic equivalence theorem (MBET). The new method is based on the Born approximation and has features: 1) a scattered field including not only a far-field (FF) but also a near-field (NF) can be predicted from measured NF samples, where the measurement distances from a target under test to the TX and RX can be different; 2) the scattered field with a zero bistatic angle and the field with the nonzero bistatic angle where the MBET holds can be predicted; 3) the computational time is practical for a large target; and 4) the implementation of the code is easy. The algorithm of the method has simply three steps: inverse Fourier transformation (FT) is implemented with the measured NF samples, the samples with inverse FT are multiplied by a novel weighting factor, and the scattered field is predicted by taking FT of the weighted samples. The proposed method is experimentally and numerically verified.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Observed Over-the-Horizon Propagation Characteristics and Evaporation Duct
           Inversion During the Entire Process of Tropical Cyclone Mulan (202207)

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      Authors: Shuwen Wang;Kunde Yang;Yang Shi;Fan Yang;Hao Zhang;
      Pages: 5322 - 5334
      Abstract: An evaporation duct, which often occurs in the air–sea boundary layer, has a considerable impact on the remote sensing detection capability of electromagnetic (EM) systems. Tropical cyclones (TCs) substantially increase the transfer of water vapor and heat in the air–sea boundary and inevitably affect EM propagation environments; however, observations of duct environments and their effects on EM propagation during a TC process have seldom been reported. In this article, X-band EM propagation systems that can operate continuously in the TC environment were specially developed, and observations of multiple over-the-horizon propagation links during TC Mulan (202207) were presented. The path loss (PL) of five links and the surface variations both in Mulan’s area of high wind speed (WS) and eye were recorded. The average PL of a 53-km link was approximately 155 dB in the high WS area, while a 30 dB increase in PL was detected in Mulan’s eye. The inversion and simulation results show that the evaporation duct height (EDH) was high in the high WS area, which led to low PL in EM propagation; conversely, EDH was low inside Mulan’s eye, resulting in high PL.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • On Dynamic Ray Tracing and Anticipative Channel Prediction for Dynamic
           Environments

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      Authors: Denis Bilibashi;Enrico M. Vitucci;Vittorio Degli-Esposti;
      Pages: 5335 - 5348
      Abstract: Ray tracing (RT) algorithms, which can simulate multipath radio propagation in the presence of geometric obstacles such as buildings, objects, or vehicles, are becoming quite popular, due to the increasing availability of digital environment databases and high-performance computation platforms, such as multicore computers and cloud computing services. When objects or vehicles are moving, which is the case of industrial or vehicular environments, multiple successive representations of the environment (“snapshots”) and multiple RT runs are often necessary, which require a great human effort and a great deal of computation resources. Recently, the dynamic RT (DRT) approach has been proposed to predict the multipath evolution within a given time lapse on the base of the current multipath geometry, assuming constant speeds and/or accelerations for moving objects, using analytical extrapolation formulas. This is done without rerunning a full RT for every “snapshot” of the environment, therefore with a great reduction in both human labor and computation time. When DRT is embedded in a mobile radio system and used in real time, ahead-of-time (or anticipative) field prediction is possible, which opens the way to interesting applications. In the present work, a full-3-D DRT algorithm is presented, which allows to account for multiple reflections, edge diffraction, and diffuse scattering for the general case where moving objects can translate and rotate. For the purpose of validation, the model is first applied to some ideal cases and then to realistic cases where results are compared with conventional RT simulation and measurements available in the literature.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Non-Kronecker Structured PFS Method for Channel Emulation in Multiprobe
           OTA Setups

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      Authors: Lijian Xin;Yong Li;Hao Sun;Guiming Wei;
      Pages: 5349 - 5360
      Abstract: The realistic channel environment can be characterized by a geometry-based stochastic channel (GBSC) model composed of multiple clusters, each of which consists of many rays. For the GBSC model, the power angle of arrival (AoA) spectrum of a cluster depends on the power angle of departure-Doppler (AoD-Doppler) spectrum. Hence, this model is non-Kronecker structured. In over-the-air (OTA) testing, the prefaded signal synthesis (PFS) method is valid for emulating the GBSC to measure devices under test (DUTs). However, the emulated channel under the conventional PFS method is a Kronecker case due to the independently and identically distributed (i.i.d.) fading sequences between probes when synthesizing clusters. It will lead to inaccurate link characteristics for emulation. Therefore, a non-Kronecker structured PFS (NKSPFS) method is proposed. Specifically, the rays mapped to probes are individually weighted to ensure that fading sequences between probes are independent but not identically distributed. To determine the ray weights without degrading marginal correlations for emulation, the constraints are introduced on the deviation between the target spatial–temporal correlation and the emulated spatial–temporal correlation according to the emulated spatial correlation and temporal correlation. Simulation results show that the proposed NKSPFS method outperforms the conventional PFS method in OTA testing of multi-antenna devices.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Multimode and Reconfigurable Phase Shifter of Spoof Surface Plasmons

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      Authors: Xinxin Gao;Wen Yi Cui;Ze Gu;Jingjing Zhang;Yi Ren;Qian Ma;Tie Jun Cui;
      Pages: 5361 - 5369
      Abstract: Traditional phase shifters (PSs) are mainly focused on phase performance and rarely consider the phase shift between different electromagnetic (EM) modes, limiting their widespread applications. Spoof surface plasmon polaritons (SSPPs) support EM waves with strong field confinements, giving rise to the time delay of signals. Due to the flexible dispersion behaviors, SSPPs can be engineered at will by designing the plasmonic structure parameters. Benefitting from these characteristics, here we propose a multimode and reconfigurable SSPP PS loaded with varactor diodes. By controlling the dispersion behaviors, phase differences between different SSPP modes can be realized, and the phase shift of each mode can be reconfigured. Experimental results show that the proposed SSPP PS can achieve about 240°, 241°, and 340° phase shifts among the fundamental (even) modes, the high-order (odd) modes, and the fundamental and high-order modes, respectively, by switching the bias voltages applied to the varactors. Additionally, the proposed SSPP PS has the capability to continuously tune the phase difference in each mode. Simulations and measurements have a good consistency. This work lays the groundwork for SSPP applications in large-scale integrated circuits and wireless communication systems and has a promising application in Terahertz circuits.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Over-the-Air Noise Temperature Measurement

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      Authors: Haidong Chen;Shuai Wang;Huixiong Huang;Weijie Lin;Wenquan Che;Quan Xue;
      Pages: 5370 - 5377
      Abstract: Noise temperature is one of the key performances of RF components, such as the amplifiers in those receivers and transmitters. It is essential to measure the noise temperature accurately; however, the traditional conduction method is no longer suitable for those components with integrated antennas, e.g., antennas in packages (AiPs) or antenna on chip (AoC). This article proposes a solution for noise temperature measurement based on the over-the-air (OTA) method. First, the concept and the problem of noise temperature for those devices integrated with RF components and radiation elements are reviewed, the proposed OTA noise temperature measurement and calibration methods are presented, the measurement systems are set up and at both C-band and millimeter-wave band with different measurement distances under both transmitting and receiving states are demonstrated in detail, and the measured results are compared and discussed which verifies that this proposed method is technically feasible for the OTA noise temperatures with high accuracy.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Convolutional Neural Network for Parameter Estimation of the Bi-GTD
           Model

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      Authors: Xiao-Yu Xing;Hua Yan;Hong-Cheng Yin;Chao-Ying Huo;
      Pages: 5378 - 5391
      Abstract: In this article, a novel parameter estimation method based on a convolutional neural network (CNN) is proposed to extract the geometrical features of radar objects. The CNN’s design is inspired by the inversion process of a physically relevant model, called the geometrical theory of diffraction (GTD) model, whose bistatic form can be used to describe the bistatic scattering response from the target in the netted radar system. This model-inspired inversion method can automatically compensate for phase errors between multiple signal channels and obtain better parameter estimation performance than traditional methods, such as the orthogonal matching pursuit (OMP), the estimation of signal parameters via rotational invariance techniques (ESPRIT), and the multiple signal classification (MUSIC). The experimental results not only verify the validity of the proposed intelligent inversion method but also demonstrate the interpretability and generalization ability of the CNN, whose architecture is designed based on mathematical derivation.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Three-Port Pattern- and Polarization-Diversity Rectangular Dielectric
           Resonator Antenna

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      Authors: Bing Zhang;Jian Ren;Tian Yang;Yan-Ting Liu;Zhipeng Zhao;Junfei Zhao;Ying Liu;Yingzeng Yin;
      Pages: 5392 - 5397
      Abstract: In this communication, a compact three-port pattern- and polarization-diversity rectangular dielectric resonator antenna (DRA) is investigated. The antenna is designed based on three TE modes, $text{TE}^{x}_{delta 11}$ mode, asymmetric $text{TE}^{y}_{1delta 1}$ mode, and the presented quasi-omnidirectional mode, symmetrical $text{TE}^{y}_{1delta 1}$ mode. The radiation mechanism of the presented symmetrical $text{TE}^{y}_{1delta 1}$ mode is revealed by the theory of array and the geometric theory of diffraction. The asymmetric and symmetrical $text{TE}^{y}_{1delta 1}$ modes are supported by different boundary conditions. Based on the field-distribution difference between the two modes, an artificial boundary made of metal strips is electroplated on a portion of the side of the DRA to excite the symmetric and asymmetric $text{TE}^{y}_{1delta 1}$ modes simultaneously. For verification, a three-mode diversity DRA $^{^{^{}}}$ is designed at 5.8 GHz. The $text{TE}^{x}_{delta 11}$ , asymmetric, and symmetric $text{TE}^{y}_{1delta 1}$ modes are excited by differential probes, slot in the center, and slots at the periphery, respectively. The overlapping 10-dB bandwidth of the three ports covers from 5.7 to 5.9 GHz. The envelope correlation coefficients and mean effective gain ratios are lower than 0.13 and 1.5 dB, -espectively.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Frequency- and Pattern-Reconfigurable Antenna Array With Broadband Tuning
           and Wide Scanning Angles

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      Authors: Chang Jiang You;Shu Han Liu;Jin Xi Zhang;Xi Wang;Qin Yu Li;Guang Qiang Yin;Zhi Guo Wang;
      Pages: 5398 - 5403
      Abstract: A frequency- and pattern-reconfigurable $1times4$ array is analyzed and designed, which consists of a reconfigurable feed network, 12 rectangular parasitic patches, and four octagonal patch antennas. Characteristic mode analysis (CMA) is used to study the radiation characteristics of the proposed element antenna. By changing the ON–OFF states of 18 p-i-n diodes loaded in the feed network, different combinations of the initial current phase are obtained to realize the reconfiguration of five radiation states. By loading varactor diodes and parasitic patches, frequency reconfigurability is achieved. The measured result shows that the array pattern can be discretely switched in the directions of 0°, ±15°, ±25°, ±30°, and ±55°. The tunable overlapped −10-dB impedance bandwidth is 3.54–4.46 GHz for the five radiation patterns. The maximum gain reaches 7.67 dBi and the overlapped relative bandwidth of five radiation states is more than 22%.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Wideband Differential-Fed Microstrip Patch Antenna Based on Quad-Mode
           Resonance With Radiation Patterns Correction

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      Authors: Shu Feng;Li Zhang;Zibin Weng;Yong-Chang Jiao;
      Pages: 5404 - 5409
      Abstract: A wideband differential-fed microstrip patch antenna (DMPA) based on quad-mode resonance with radiation patterns correction is proposed in this communication. First, the common problems presented in multi-mode resonant microstrip patch antenna (MPA) are introduced: it is difficult for the numbers of operation modes to exceed two, and there are radiation nulls emerged in the broadside. Second, the physical structure and mode combination process of the DMPA are demonstrated in detail. Third, through the equivalent magnetic current array model, we comprehensively introduce the principles and processes of radiation patterns correction. Finally, a prototype is fabricated and measured. The measuring results are consisted with simulation ones. The proposed DMPA achieves 29.4% (3.22–4.33 GHz) impedance bandwidth at the profile of $0.058lambda $ (center frequency wavelength), and it has a stable gain in broadside without radiation nulls.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Metasurface-Covered Planar Endfire Antenna With Vertical Polarization

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      Authors: You-Feng Cheng;Zhi-Heng Gao;Wei-Jun Chen;Cheng Liao;Xiao Ding;
      Pages: 5410 - 5415
      Abstract: A trapped wave-based solution to design compact planar vertically polarized (VP) endfire antennas is proposed in this communication. By placing a four-element series-fed magnetic dipole array with an interspacing of half wavelength within a dual-layer metasurface and loading shorting pin arrays at two edges of the metasurface, the VP radiation is realized in a wide impedance band. In addition, the antenna profile can be further reduced by half according to the electric field distribution within the metasurface. Finally, a VP endfire antenna with a reflection bandwidth of 4.3–5.4 GHz, a peak gain of 9.8 dBi, and a low total profile of $0.065lambda_{0}$ ( $lambda_{0}$ is the free-space wavelength at the center operation frequency) is designed for the validation. The proposed antenna can be used for some wireless communication systems on or near the ground plane, such as the car roof-mounted terminal for vehicle-to-road side unit/base station communication.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Analysis of a Strip Antenna Located at a Plane Interface of Uniaxial
           Metamaterials

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      Authors: Anna S. Zaitseva;Alexander V. Kudrin;Tatyana M. Zaboronkova;
      Pages: 5416 - 5421
      Abstract: A rigorous solution is found to the problem of determining the current distribution and input impedance of a straight strip antenna located at a plane interface of two uniaxial metamaterials. The anisotropy axes of the metamaterials are parallel to each other and to the medium interface. The antenna is oriented perpendicular to these axes and excited by a given time-harmonic voltage. Using the Fourier transform technique, singular integral equations for the antenna current are derived and solved for all possible combinations of the metamaterial parameters. Closed-form representations for the current distribution and input impedance of an infinitely long strip are obtained and their generalization to the case of a finite-length antenna is discussed.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Novel Wideband Tightly Coupled Dual-Polarized Reflectarray Antenna

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      Authors: Wenting Li;Hancheng Tu;Yejun He;Long Zhang;Sai-Wai Wong;Steven Gao;
      Pages: 5422 - 5427
      Abstract: In this communication, a novel tightly coupled dual-polarized reflectarray antenna is presented. The antenna consists of a dual-polarized feed antenna and a wideband dual-polarized reflecting surface. The reflecting surface is composed of dual-polarized tightly coupled unit cells. Each unit cell contains two types of elements, of which the polarizations are perpendicular. Each element contains a dipole and a delay line. For one polarization, the reflecting surface consists of $13 times 34$ elements, while there are $26 times 11$ elements on the reflecting surface for the other polarization. The feed antenna is a wideband dual-polarized horn antenna. The phase error distribution on the reflecting surface is analyzed as well. To verify the design, a prototypical tightly coupled dual-polarized reflectarray antenna operating from 3 to 8 GHz is simulated, manufactured, and measured. The simulated results are in good agreement with the measured results. In the working band, the radiation patterns of the proposed reflectarray antenna are stable.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Low-Profile Polarization-Twisting Cassegrain Antenna for Generating Dual
           Circularly Polarized Multibeam Radiation in Ku-Band

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      Authors: Pei Yang;Bo Dang;Zhiping Ren;Ruirong Dang;
      Pages: 5428 - 5433
      Abstract: In this communication, a low-profile polarization-twisting Cassegrain antenna (LPPTCA) is proposed to generate dual circularly polarized (CP) multibeam radiation by integrating multifunctional metasurface (MM), polarization conversion metasurface (PCM), and multiple microstrip feeds. Considering that the LPPTCA removes the occlusion effect from the traditional Cassegrain antenna, the profile height of LPPTCA will be chosen as 1/3 focal length of PCM and can also be freely adjusted when employing corresponding phase gradient over the MM to mimic the hyperbolic reflector of the traditional Cassegrain antenna. The MM is capable of achieving the functionality of reflecting co-LP waves with performing diverged wave fronts and transmitting cross-LP waves with linear-to-dual-circular polarization conversion. Based on the MM and PCM, the LPPTCA is designed and fabricated; then, measurement results illustrate that the LPPTCA is capable of realizing dual CP multibeam radiation in the range of 13.7–14.7 GHz when employing multiple microstrip antennas as feeds. In the meanwhile, the scanning range of multibeams is ± 20 ° with the minimum feed isolation of 15 dB. The proposed dual CP multibeam LPPTCA integrating the MM and PCM should, thus, pave the way for building up current and future wireless communication systems with millimeter-wave MIMO applications in Ku-band.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Broadband Fixed-Beam Leaky-Wave Antenna

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      Authors: Hang Du;Zheng Li;Meie Chen;Junhong Wang;
      Pages: 5434 - 5439
      Abstract: In point-to-point communication, antennas are often required to radiate a broadband signal in a specific direction. Traditional leaky-wave antennas (LWAs) have the features of low cost and high gain but also the frequency-beam-scanning property, which is not suitable for this demand. In this communication, an LWA with broadband fixed-beam property is designed in millimeter-wave band. The antenna is implemented on a ridge gap waveguide (RGW), and a series of microstrip branches are employed as phase delay lines. The working principle of the antenna is elaborated, and the main beam can be designed in any direction (including broadside and inclined angles) by selecting proper lengths for the microstrip branches. Sidelobe levels (SLLs) can be reduced by using slots with gradually changed lengths to excite the microstrip branches. Three antennas with main beam directions in 0° and ±25° are designed and measured as verifications. In the experiment, the antennas show stable radiation properties (including beam angles and realized gains) over the band from 25 to 39 GHz (a bandwidth of 43%). This LWA shows potentials in millimeter-wave broadband applications.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Broadband, Low-Profile, Planar Reflectarray Antenna Based on an Achromatic
           Metasurface

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      Authors: Jianing Yang;Hai Xin;Ming-Chun Tang;
      Pages: 5440 - 5445
      Abstract: This communication presents a broadband, low-profile, and planar reflectarray (RA) antenna based on an achromatic metasurface. The achromatic metasurface has advantageous broadband focusing capabilities compared to conventional RAs. Six types of unit cells offering versatile phase responses are employed to design an achromatic metasurface optimized by a convolutional algorithm. A broadband achromatic RA antenna with a diameter of 270 mm is simulated, fabricated, and tested. The test results agree well with the simulated results. Notably, the 3 dB realized gain of the RA antenna reaches a fractional bandwidth of 58.2% at a range of 8.9–16.2 GHz. Furthermore, the RA antenna significantly enhances the feeding antenna’s gain from 7.3 to 17 GHz. The reflecting metasurface also has a low profile of $0.11~lambda text{L}$ , where $lambda text{L}$ is the wavelength in free space at 7.3 GHz. With excellent broadband performance, high gain, low profile, and ease of fabrication, the developed RA antenna serves as a promising device for long-distance integrated communication systems.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Control of Time-Reversal Aperture by High-Precision Phase-Modulated and
           Dual-Polarized Metasurface

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      Authors: Xu Han;Shuai Ding;Qing-Song Jia;Wei-Hao Zhang;Hao Tang;Zhengping Zhang;Xiong Wang;Yuliang Zhou;Yong-Mao Huang;Bing-Zhong Wang;
      Pages: 5446 - 5451
      Abstract: In this communication, we propose a novel design concept for the generation of special beams based on time-reversal aperture (TRA) theory. First, different forms of TRAs are investigated to overcome the shortcomings of traditional TRA in special beam generation. Next, a wideband (26.11% for TE and 19.5% for TM, respectively) dual-polarization phase-modulation metasurface (MS) is designed. Subsequently, the designed MS illuminated by TE plane wave will generate sloping Bessel Beam, meanwhile, the accelerating beam will be generated by TM plane wave incident. Compared to the classical methods, the proposed MS not only achieves a dual-polarization independent phase shift range of more than 400° without dimensional changes but also maintains a high transmittance with transmission loss lower than 0.3 dB. Finally, to verify the concept, the MS is manufactured and tested. The measured results show good agreement with the theoretic demonstrations and full-wave simulations.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Fully Analytical Design of Dual-Wire PCB Metagratings for Beam Steering
           and Splitting

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      Authors: Zhen Tan;Jianjia Yi;Xiaoming Chen;Menglan Lin;Zhi Hao Jiang;Douglas H. Werner;Shah Nawaz Burokur;
      Pages: 5452 - 5456
      Abstract: The printed circuit board (PCB)-type metagrating (MG), a periodic microstrip planar structure with discrete distribution of polarization currents, can realize high-angle wavefront shaping with near-unity efficiency for potential application in high beam-steering antennas or reflectors. For large-angle deflection, only a small number of meta-atoms are required in the MG’s period. As such, here, we focus on a reflective PCB MG in the presence of only two meta-atoms, whose complex load impedance densities are explicitly derived from fully analytical expressions. The passive and lossless conditional equations as well as the equations for the power ratio control of the diffraction modes are given, which allows avoiding numerical optimization procedure. Three practical prototypes, including anomalous reflector and beam splitters, are designed, simulated, and measured. The measurement results agree well with the simulation results and are consistent with the theoretical predictions.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Rotated Feed-Combined Reconfigurable Transmit RIS With Disparate
           Deployment of 1-bit Hybrid Units for B5G/6G

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      Authors: Jaehoon Kim;Jinhyun Kim;Jun Hwa Oh;Sang-Hyuk Wi;Jungsuek Oh;
      Pages: 5457 - 5462
      Abstract: This communication presents an initial disparate deployment of 1-bit hybrid units using p-i-n diodes in transmit reconfigurable intelligent surface (TRIS) combined with a rotated feed source to address the gain limitation of the existing 1-bit TRIS. Two types of hybrid units, with a radiation phase difference of 90° by the delay line, are proposed in this study. The TRIS aperture is divided into two sections based on two different radiation centers by rotated feed, and the hybrid units in each Section are initially configured to implement optimized quasi 2-bit beam collimation in the 0° and 40° for enhanced quantization loss. It is found that the array envelope is higher even in radiation directions other than the optimized directions, despite the initial disparate deployment of each section. Beamforming for –theta direction in the H-plane is only considered for the proof of concept with the smallest size of TRIS aperture. A $16times16$ ( $7.6times 7.6,,lambda_{0}$ at 28 GHz) 1-bit hybrid TRIS offers gain enhancement of 0–5.6 dB in −70 ° to −0 ° directions of the array envelope compared with the conventional 1-bit TRIS. The proposed 1-bit hybrid TRIS yields an improved aperture efficiency of 24.4%.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Millimeter-Wave Wide-Angle Scanning Phased Array Antenna Based on
           Heterogeneous Beam Elements

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      Authors: Guiping Jin;Yi Sun;Shaowei Liao;Quan Xue;
      Pages: 5463 - 5468
      Abstract: By imitating the element-inclined beam distribution of a curved surface conformal (CSC) phased array antenna (PAA), a pseudo-CSC (PCSC) PAA realizes wide-angle scanning while maintaining a planar low profile. Inspired by the PCSC PAA, this communication proposes a PAA based on heterogeneous beam elements (HBEs) to realize wide-angle scanning. Using HBEs introduces a new design degrees of freedom (DoFs), namely the element beam shape, to PAA. By optimizing HBEs and their arrangement, the effective aperture of a PAA can be increased at large scanning angles, and thus the scanning range can be improved. To verify the idea, first, a wide-beam $1times4$ -element subarray is developed. Then, a standard $4times4$ -element PAA is implemented using four uniform $1times4$ -element subarrays, achieving a $>pm 60^{circ }$ 3-dB gain variation scanning range. At last, based on the standard PAA, by adjusting its structure to tailor four subarrays’ beam inclinations, a $4times4$ -element HBE PAA is designed. It further improves the scanning range to $>pm 70^{circ }$ at an average cost of ~1.5 dBi broadside scanning gain within the 5G mmWave band (24.25–29.5 GHz, 19.5%). To the authors’ best knowledge, compared with the former planar mmWave PAAs, the proposed design shows the widest scanning range in a wide bandwidth.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Wideband Dual-Polarized Endfire Phased Array Antenna With Small Ground
           Clearance for 5G mmWave Mobile Terminals

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      Authors: Yuqing Zhu;Changjiang Deng;
      Pages: 5469 - 5474
      Abstract: A dual-polarized endfire phased array antenna is presented for 5G mmWave mobile terminal applications. The antenna element combines a pair of top-hat dipoles with an open slot in two substrate layers. The dipole is excited by an open-ended substrate integrated waveguide (SIW) for vertical polarization, and the slot is coupled by a bent stripline for horizontal polarization. Both radiators can provide wide bandwidth, and share a small ground clearance of merely 1.6 mm. A $1times4$ phased array is designed with an element spacing of 6 mm. Decoupling vias and decoupling slots are added between elements to improve port isolation. The simulated and measured overlapped bandwidth of the two polarizations are 21.4% and 14.6%, respectively. The isolation between any two ports is higher than 18 dB. The measured scanning beams of both polarizations are capable of covering ±42° within 3-dB gain variation.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Wideband 1-bit Reconfigurable Electromagnetic Surface for Monopulse
           Radar Applications

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      Authors: Xiangjin Ma;Jiaqi Han;Guanxuan Li;Mingyang Chang;Yucen Tian;Silong Chen;Haixia Liu;Long Li;Tie Jun Cui;
      Pages: 5475 - 5480
      Abstract: We present a wideband 1-bit reconfigurable electromagnetic surface (REMS) for monopulse radar applications at X-band. The proposed REMS element integrates a 1-bit reflection-type phase shifter (RTPS) controlled by a p-i-n diode. By altering the working states of the p-i-n diode, well-defined beam scanning is obtained. Furthermore, selecting different feeding states can realize the sum ( $Sigma$ ) and difference ( $Delta$ ) patterns. The key design issues, including element modeling, coding design, and feed optimization, are studied to obtain good $Sigma $ and $Delta $ beam performance. Experimental results show that REMS achieves a high gain of 23.3 dBi, a low sidelobe level of −15 dB, and a low null depth of −30 dB. The wide-angle monopulse beam-scanning up to ±60° is obtained. The gain bandwidth of −3 dB ranges from 9.35 to 11.75 GHz, with a relative bandwidth of 22.75%. Thus, the proposed multifeed REMS brings new freedom for the $Sigma $ and $Delta $ beam scanning, which provides wide application prospects for the monopulse radar system.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Electromagnetic Transmit Array With Optical Control for Beamforming

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      Authors: Wei Zhang;Javad Meiguni;Yin Sun;Muqi Ouyang;Xin Yan;Xu Wang;Reza Yazdani;Daryl Beetner;Donghyun Kim;David Pommerenke;
      Pages: 5481 - 5486
      Abstract: This proof-of-concept communication demonstrates the feasibility of using a slide projector to steer the beam of a transmit array by adding solar cells and varactor diodes to each unit cell. By irradiating each solar cell with the light of different intensities from a slide projector, the measured phase of the wave transmitted by the $4times4$ transmit array shifts within 92° at 4.26 GHz, while the variation in magnitude is measured within 4 dB. Different light configurations are identified via a searching algorithm to achieve peak/null beamforming in a particular direction. The beam of the prototypical $4times4$ transmit array can be shifted by ±24° in terms of the peaks and −30° to 36° in terms of nulls. The concept of adding light modulation to the transmit array with a slide projector can provide update rates of tens of milliseconds with control of brightness and color distributed over a large area of the array.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Wideband Sherman–Morrison–Woodbury Formula-Based Algorithm for
           Electromagnetic Scattering Problems

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      Authors: Xinlei Chen;Liyang Zhang;Changqing Gu;Zhuo Li;
      Pages: 5487 - 5492
      Abstract: In this communication, a wideband Sherman–Morrison–Woodbury formula-based algorithm (WSMWA) is proposed to efficiently compute the wideband and wide-angle electromagnetic scattering problems. In the proposed algorithm, the standard adaptive cross approximation (ACA) decomposition is only performed at the highest frequency of the frequency band of interest to find the dominant basis functions for each far-block pair. Then, at any frequency within the entire frequency band, the approximate compression of the impedance matrix can be efficiently constructed by using the impedance interpolation method with the dominant basis functions selected at the highest frequency. As a result, the WSMWA avoids performing the standard ACA repeatedly and saves a lot of computational time in comparison with the conventional Sherman–Morrison–Woodbury formula-based algorithm (SMWA) for wideband and wide-angle applications. Numerical results for electromagnetic scattering are given to demonstrate the efficiency and accuracy of the proposed algorithm.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • On Preconditioners of the FFT-JVIE for Inhomogeneous Dielectric Objects

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      Authors: Si-Zhuo Gu;Liang Zhang;Da-Miao Yu;Kui-Wen Xu;Li-Ming Si;Xiao-Min Pan;
      Pages: 5493 - 5497
      Abstract: An improved block-diagonal preconditioner (IBDP) is developed for the fast Fourier transform (FFT) accelerated the volume integral equation formulation based on equivalent volumetric currents (FFT-JVIE). A comparative study on the realistic models is carried out among the IBDP, block-diagonal preconditioner (BDP), the previously developed analytical preconditioner (AnP), and the circulant-based preconditioners (CBPs).
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Surrogate Modeling Approach for Frequency-Reconfigurable Antennas

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      Authors: Yuming Bai;Peter Gardner;Yijing He;Houjun Sun;
      Pages: 5498 - 5503
      Abstract: A novel generalizable surrogate modeling approach is specifically developed for frequency-reconfigurable antennas. The generalizable modeling processes is based on the rigorous mathematical derivation, including the solution of a nonlinear overdetermined system, the optimization in the complex field, and the interpolation in multidimensional continuous space. As a postprocessing method, the approach can convert the discrete data of CAD simulation to a surrogate model. Subsequently, a reconfigurable UWB antenna with a tunable notch band is taken as an example to demonstrate that the surrogate modeling approach is feasible, effective, and precise. It also has the flexible ability to adapt to strict requirements and complicated scenarios. The proposed surrogate model is a good candidate for the interface standard between a reconfigurable antenna and signal processing part in a cognitive radio (CR) system.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Intelligent Prediction for Scattering Properties Based on Multihead
           Attention and Target Inherent Feature Parameter

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      Authors: De-Hua Kong;Wen-Wei Zhang;Xiao-Yang He;Ming-Yao Xia;
      Pages: 5504 - 5509
      Abstract: In this communication, an artificial intelligent method based on the prevailing multihead attention mechanism for prediction of scattering properties of 2-D targets is presented. To make the predicting approach independent of the incident direction of an excitation plane wave, a kind of inherent feature parameters (IFPs) for a specific target is defined and applied as the output of the artificial neural network (ANN). Two types of targets are experimented, one of which is composed of polygons and the other of smooth shapes. Numerical results show that the proposed method has satisfactory prediction accuracy and computing speed, as well as good generalization ability.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • A Simple Way of Applying the Calderón Preconditioner to a Finite-Element
           Boundary-Integral Method

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      Authors: Yiqian Mao;Yang Zhong;Qiwei Zhan;Dezhi Wang;Qing Huo Liu;
      Pages: 5510 - 5515
      Abstract: The Calderón preconditioner effectively improves the convergence of the iterative solution of surface integral equations (SIEs). This work presents an alternative way to apply the Calderón preconditioner to a finite-element boundary-integral system, as well as a twofold iterative solver where the finite-element subsystem and boundary-integral subsystem are preconditioned separately. In this approach, the finite-element domain can utilize second-order basis functions to reduce the number of unknowns required for scatterers with large dielectric constants. Numerical experiments are provided to compare the accuracy and convergence of the proposed method with the approach based on the Poincaré–Steklov (PS) operator.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Sliding Scattering Center Extraction for Streamlined Radar Targets

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      Authors: Kejiang Wu;Wei Cui;Xiaojian Xu;
      Pages: 5516 - 5521
      Abstract: Modern man-made targets with high-speed movement capabilities are often designed as special streamlined structures. As a result, when illuminated by radar, the surface of such targets will produce a sliding scattering center (SSC) whose position changes with the radar line of sight (RLOS). In this communication, we present a feature extraction technique for this kind of scattering center. The trajectory of the equivalent scattering points in the 1-D high-resolution range profile (HRRP) sinogram is first predicted by utilizing the special geometric characteristics of sliding scatterers. The parameters of sliding scattering features are then extracted by combining the basis pursuit algorithm with the predicted trajectory. Examples from both numerical and measured data are presented to demonstrate the usefulness of the proposed technique.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Enhanced Misalignment Estimation of Orbital Angular Momentum Signal Based
           on Deep Recurrent Neural Networks

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      Authors: Jia-Jing Sun;Sheng Sun;Ling-Jun Yang;Jun Hu;
      Pages: 5522 - 5527
      Abstract: This communication presents a deep-learning-based approach to quantitatively extract misalignment information in the orbital angular momentum (OAM) radio communication systems. It is shown that the misaligned field exhibits unique sequence-based features for different misalignment information. Consequently, the recurrent neural network (RNN), a powerful method to deal with sequential data, is introduced to extract its intrinsic features and estimate the misalignment values. To further reduce the total number of parameters as well as to improve the performance, a gated recurrent unit (GRU) is employed to construct the recurrent layer. As far as we know, this is the first use of deep learning for the estimation of the OAM misalignment information in radio frequency (RF). The setup of the training data and the performance of the proposed model under four different misalignment cases are demonstrated. To further validate the reliability of the proposed models, the trained model is evaluated on the sample carrying 20% Gaussian noise. Furthermore, the effects of the position deviation and the number of samples are also investigated. Besides, the comparison with other methods is presented. It is illustrated that the tailored model can reach the same measurement resolution as the previous literature while requiring only one-eighth of the sampling points.
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
  • Special Issue Measurement Technologies for Emerging 5G and Beyond Channel
           Characterization and Antenna Systems

    • Free pre-print version: Loading...

      Pages: 5528 - 5528
      PubDate: June 2023
      Issue No: Vol. 71, No. 6 (2023)
       
 
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