Subjects -> ENGINEERING (Total: 2688 journals)
    - CHEMICAL ENGINEERING (229 journals)
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    - ELECTRICAL ENGINEERING (176 journals)
    - ENGINEERING (1325 journals)
    - ENGINEERING MECHANICS AND MATERIALS (452 journals)
    - HYDRAULIC ENGINEERING (56 journals)
    - INDUSTRIAL ENGINEERING (98 journals)
    - MECHANICAL ENGINEERING (115 journals)

ENGINEERING (1325 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 1205 Journals sorted by number of followers
Composite Structures     Hybrid Journal   (Followers: 245)
IEEE Spectrum     Full-text available via subscription   (Followers: 219)
Composites Part B : Engineering     Hybrid Journal   (Followers: 219)
ACS Nano     Hybrid Journal   (Followers: 181)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 173)
IEEE Geoscience and Remote Sensing Letters     Hybrid Journal   (Followers: 150)
Composites Science and Technology     Hybrid Journal   (Followers: 150)
IEEE Instrumentation & Measurement Magazine     Hybrid Journal   (Followers: 148)
IEEE Communications Magazine     Full-text available via subscription   (Followers: 139)
IEEE Engineering Management Review     Full-text available via subscription   (Followers: 117)
IEEE Antennas and Propagation Magazine     Hybrid Journal   (Followers: 112)
IEEE Transactions on Control Systems Technology     Hybrid Journal   (Followers: 111)
IEEE Transactions on Instrumentation and Measurement     Hybrid Journal   (Followers: 106)
IEEE Transactions on Signal Processing     Hybrid Journal   (Followers: 92)
IEEE Antennas and Wireless Propagation Letters     Hybrid Journal   (Followers: 88)
IEEE Industry Applications Magazine     Full-text available via subscription   (Followers: 82)
IEEE Transactions on Antennas and Propagation     Full-text available via subscription   (Followers: 79)
IEEE Transactions on Engineering Management     Hybrid Journal   (Followers: 74)
Engineering Failure Analysis     Hybrid Journal   (Followers: 68)
IEEE Microwave Magazine     Full-text available via subscription   (Followers: 63)
IEEE Signal Processing Letters     Hybrid Journal   (Followers: 60)
IEEE Transactions on Reliability     Hybrid Journal   (Followers: 53)
Experimental Techniques     Hybrid Journal   (Followers: 51)
IET Radar, Sonar & Navigation     Open Access   (Followers: 50)
IEEE Transactions on Microwave Theory and Techniques     Hybrid Journal   (Followers: 49)
Control Engineering Practice     Hybrid Journal   (Followers: 46)
IEEE Journal of Selected Topics in Signal Processing     Hybrid Journal   (Followers: 43)
Biotechnology Progress     Hybrid Journal   (Followers: 42)
IEEE Potentials     Full-text available via subscription   (Followers: 42)
IEEE Journal on Selected Areas in Communications     Hybrid Journal   (Followers: 39)
Heat Transfer Engineering     Hybrid Journal   (Followers: 36)
IET Microwaves, Antennas & Propagation     Open Access   (Followers: 35)
International Journal for Numerical Methods in Engineering     Hybrid Journal   (Followers: 35)
IEEE Microwave and Wireless Components Letters     Hybrid Journal   (Followers: 35)
Digital Signal Processing     Hybrid Journal   (Followers: 34)
IEEE Transactions on Knowledge and Data Engineering     Hybrid Journal   (Followers: 32)
AIChE Journal     Hybrid Journal   (Followers: 31)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 31)
Computers & Geosciences     Hybrid Journal   (Followers: 30)
Flow, Turbulence and Combustion     Hybrid Journal   (Followers: 30)
Coastal Management     Hybrid Journal   (Followers: 29)
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 28)
GPS Solutions     Hybrid Journal   (Followers: 28)
Fluid Dynamics     Hybrid Journal   (Followers: 27)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 27)
Géotechnique     Hybrid Journal   (Followers: 27)
IEEE Transactions on Information Theory     Hybrid Journal   (Followers: 27)
IEEE Transactions on Power Delivery     Hybrid Journal   (Followers: 26)
Applied Energy     Partially Free   (Followers: 26)
Advances in Engineering Software     Hybrid Journal   (Followers: 26)
IEEE Journal of Solid-State Circuits     Full-text available via subscription   (Followers: 24)
Corrosion Science     Hybrid Journal   (Followers: 23)
Engineering & Technology     Hybrid Journal   (Followers: 22)
IET Image Processing     Open Access   (Followers: 22)
Intermetallics     Hybrid Journal   (Followers: 21)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 21)
IEEE Transactions on Electronics Packaging Manufacturing     Hybrid Journal   (Followers: 21)
IET Signal Processing     Open Access   (Followers: 21)
IEEE Transactions on Circuits and Systems II: Express Briefs     Hybrid Journal   (Followers: 20)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 20)
Implementation Science     Open Access   (Followers: 20)
International Journal for Numerical Methods in Fluids     Hybrid Journal   (Followers: 19)
Engineering Optimization     Hybrid Journal   (Followers: 19)
International Communications in Heat and Mass Transfer     Hybrid Journal   (Followers: 19)
Electrophoresis     Hybrid Journal   (Followers: 18)
IET Circuits, Devices & Systems     Open Access   (Followers: 18)
IEEE/ACM Transactions on Computational Biology and Bioinformatics     Hybrid Journal   (Followers: 18)
International Journal of Adhesion and Adhesives     Hybrid Journal   (Followers: 18)
IEEE Transactions on Intelligent Transportation Systems     Hybrid Journal   (Followers: 17)
Experiments in Fluids     Hybrid Journal   (Followers: 17)
Computational Geosciences     Hybrid Journal   (Followers: 17)
Integration     Hybrid Journal   (Followers: 16)
IEEE Transactions on Energy Conversion     Hybrid Journal   (Followers: 16)
Engineering Geology     Hybrid Journal   (Followers: 16)
European Journal of Mass Spectrometry     Hybrid Journal   (Followers: 16)
Energy Conversion and Management     Hybrid Journal   (Followers: 15)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 15)
Coastal Engineering     Hybrid Journal   (Followers: 15)
IEEE Transactions on Magnetics     Hybrid Journal   (Followers: 14)
IEEE Journal of Biomedical and Health Informatics     Hybrid Journal   (Followers: 14)
IEEE Transactions on Automation Science and Engineering     Full-text available via subscription   (Followers: 13)
IEEE Transactions on Evolutionary Computation     Hybrid Journal   (Followers: 13)
Electromagnetics     Hybrid Journal   (Followers: 13)
Computers and Geotechnics     Hybrid Journal   (Followers: 12)
IEEE Transactions on Semiconductor Manufacturing     Hybrid Journal   (Followers: 12)
IET Renewable Power Generation     Open Access   (Followers: 12)
Human Factors in Ergonomics & Manufacturing     Hybrid Journal   (Followers: 12)
IEEE Transactions on Professional Communication     Hybrid Journal   (Followers: 11)
Biomedical Engineering     Hybrid Journal   (Followers: 11)
IEEE Transactions on Education     Hybrid Journal   (Followers: 11)
CIRP Annals - Manufacturing Technology     Hybrid Journal   (Followers: 11)
IEEE Journal of Oceanic Engineering     Hybrid Journal   (Followers: 11)
Heat Transfer - Asian Research     Hybrid Journal   (Followers: 10)
International Journal of Antennas and Propagation     Open Access   (Followers: 10)
Proceedings of the Institution of Civil Engineers - Geotechnical Engineering     Hybrid Journal   (Followers: 10)
IEEE Transactions on Nuclear Science     Hybrid Journal   (Followers: 10)
IEEE Transactions on Plasma Science     Hybrid Journal   (Followers: 10)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 9)
Fuel Cells Bulletin     Full-text available via subscription   (Followers: 9)
Computational Optimization and Applications     Hybrid Journal   (Followers: 9)
Annals of Science     Hybrid Journal   (Followers: 9)
European Journal of Engineering Education     Hybrid Journal   (Followers: 9)
Applied Catalysis B: Environmental     Hybrid Journal   (Followers: 9)
Biomedical Microdevices     Hybrid Journal   (Followers: 8)
IEEE Technology and Society Magazine     Full-text available via subscription   (Followers: 8)
Fuel Cells     Hybrid Journal   (Followers: 8)
Adaptive Behavior     Hybrid Journal   (Followers: 8)
Proceedings of the Institution of Civil Engineers - Bridge Engineering     Hybrid Journal   (Followers: 8)
Energy Engineering     Full-text available via subscription   (Followers: 8)
IEEE Transactions on Advanced Packaging     Full-text available via subscription   (Followers: 8)
Clay Minerals     Hybrid Journal   (Followers: 8)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 8)
Applied Catalysis A: General     Hybrid Journal   (Followers: 7)
International Journal of Applied Ceramic Technology     Hybrid Journal   (Followers: 7)
Basin Research     Hybrid Journal   (Followers: 7)
Discrete Optimization     Full-text available via subscription   (Followers: 7)
Designs, Codes and Cryptography     Hybrid Journal   (Followers: 7)
IEEE Journal of Selected Topics in Quantum Electronics     Hybrid Journal   (Followers: 7)
Environmental and Ecological Statistics     Hybrid Journal   (Followers: 7)
Biomicrofluidics     Open Access   (Followers: 7)
Geothermics     Hybrid Journal   (Followers: 7)
Fuel and Energy Abstracts     Full-text available via subscription   (Followers: 7)
IEEE Vehicular Technology Magazine     Full-text available via subscription   (Followers: 7)
Catalysis Communications     Hybrid Journal   (Followers: 7)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 7)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 6)
Computing and Visualization in Science     Hybrid Journal   (Followers: 6)
Fusion Engineering and Design     Hybrid Journal   (Followers: 6)
Applied Clay Science     Hybrid Journal   (Followers: 6)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Formal Methods in System Design     Hybrid Journal   (Followers: 6)
Acta Geotechnica     Hybrid Journal   (Followers: 6)
Advances in OptoElectronics     Open Access   (Followers: 6)
International Journal of Adaptive Control and Signal Processing     Hybrid Journal   (Followers: 5)
IEEE Transactions on Vehicular Technology     Hybrid Journal   (Followers: 5)
IET Science, Measurement & Technology     Open Access   (Followers: 5)
IEEE Transactions on Applied Superconductivity     Hybrid Journal   (Followers: 5)
International Journal of Architectural Computing     Full-text available via subscription   (Followers: 5)
Finite Fields and Their Applications     Full-text available via subscription   (Followers: 5)
Focus on Powder Coatings     Full-text available via subscription   (Followers: 5)
Engineering With Computers     Hybrid Journal   (Followers: 5)
Proceedings of the Institution of Civil Engineers - Engineering Sustainability     Hybrid Journal   (Followers: 5)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 5)
Active and Passive Electronic Components     Open Access   (Followers: 5)
Proceedings of the Institution of Civil Engineers - Ground Improvement     Hybrid Journal   (Followers: 4)
Frontiers in Energy     Hybrid Journal   (Followers: 4)
Adsorption     Hybrid Journal   (Followers: 4)
Catalysis Today     Hybrid Journal   (Followers: 4)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 4)
Current Applied Physics     Full-text available via subscription   (Followers: 4)
Fluid Phase Equilibria     Hybrid Journal   (Followers: 4)
Graphs and Combinatorics     Hybrid Journal   (Followers: 4)
Filtration & Separation     Full-text available via subscription   (Followers: 4)
Annals of Pure and Applied Logic     Open Access   (Followers: 4)
Grass and Forage Science     Hybrid Journal   (Followers: 4)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Informatik-Spektrum     Hybrid Journal   (Followers: 3)
Engineering Computations     Hybrid Journal   (Followers: 3)
European Journal of Combinatorics     Full-text available via subscription   (Followers: 3)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 3)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 3)
Concurrent Engineering     Hybrid Journal   (Followers: 3)
Focus on Pigments     Full-text available via subscription   (Followers: 3)
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Frontiers of Environmental Science & Engineering     Hybrid Journal   (Followers: 3)
Fuzzy Sets and Systems     Hybrid Journal   (Followers: 3)
Catalysis Letters     Hybrid Journal   (Followers: 3)
IET Generation, Transmission & Distribution     Open Access   (Followers: 2)
Historical Records of Australian Science     Hybrid Journal   (Followers: 2)
IET Optoelectronics     Open Access   (Followers: 2)
Assembly Automation     Hybrid Journal   (Followers: 2)
International Journal of Abrasive Technology     Hybrid Journal   (Followers: 2)
Aerobiologia     Hybrid Journal   (Followers: 2)
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 2)
Comptes Rendus : Mécanique     Open Access   (Followers: 2)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
IEEE Latin America Transactions     Full-text available via subscription   (Followers: 2)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 2)
ESAIM: Control Optimisation and Calculus of Variations     Open Access   (Followers: 2)
Focus on Surfactants     Full-text available via subscription   (Followers: 2)
Engineering Analysis with Boundary Elements     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 1)
Foundations of Science     Hybrid Journal   (Followers: 1)
Forschung     Hybrid Journal   (Followers: 1)
European Journal of Lipid Science and Technology     Hybrid Journal   (Followers: 1)
Antarctic Science     Hybrid Journal   (Followers: 1)
Épités - Épitészettudomány     Full-text available via subscription   (Followers: 1)
Dyes and Pigments     Hybrid Journal   (Followers: 1)
Bautechnik     Hybrid Journal   (Followers: 1)
Biointerphases     Open Access   (Followers: 1)
Designed Monomers and Polymers     Open Access   (Followers: 1)
Color Research & Application     Hybrid Journal   (Followers: 1)
Abstract and Applied Analysis     Open Access   (Followers: 1)
Focus on Catalysts     Full-text available via subscription  
ESAIM: Proceedings     Open Access  
Environmetrics     Hybrid Journal  
COMBINATORICA     Hybrid Journal  
Chinese Science Bulletin     Open Access  
Calphad     Hybrid Journal  
Boundary Value Problems     Open Access  

        1 2 3 4 5 6 7 | Last

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Journal Cover
IEEE Transactions on Antennas and Propagation
Journal Prestige (SJR): 1.309
Citation Impact (citeScore): 5
Number of Followers: 79  
 
  Full-text available via subscription Subscription journal
ISSN (Print) 0018-926X
Published by IEEE Homepage  [228 journals]
  • IEEE Transactions on Antennas and Propagation

    • Free pre-print version: Loading...

      Abstract: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • IEEE Transactions on Antennas and Propagation

    • Free pre-print version: Loading...

      Abstract: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Institutional Listings

    • Free pre-print version: Loading...

      Abstract: Presents a listing of institutions relevant for this issue of the publication.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Algorithm for Fewest Arms of Multiband Linear Dipole Antenna

    • Free pre-print version: Loading...

      Authors: Bing Xiao;Hang Wong;Yichen Wei;Lawrence Kwan Yeung;
      Pages: 3144 - 3152
      Abstract: Multiband linear dipole antennas are necessary for many strip- or bar-shaped gateway devices of the Internet of Things (IoT) for connectivity under various communication protocols. However, the conventional methodology to design multiband dipole antennas is generally empirically based. More frequency bands usually mean even more arms/slots, which results in increasingly bulky size. In this article, we introduce an algorithm to use the fewest arms to design any multiband linear dipole antenna. The algorithm is based on sharing arms after the effective ranges of mode excitation are determined by characteristic mode analysis (CMA). It also applies to multiple wideband or ultrawideband antennas. By this algorithm, an exemplified pentaband dipole antenna is designed, effectively covering 433, 868, 1176, 1575, and 2450 MHz bands for low-power wide-area network (LPWAN), global navigation satellite system (GNSS), and industrial, scientific and medical (ISM) applications. The antenna has only 2.5 pairs of arms. 50% of arms are reduced in comparison to traditional methods. This algorithm significantly simplifies the structure of a multiband dipole antenna, especially suitable for strip- or bar-shaped IoT devices.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Electrically Small Antenna With a Significantly Enhanced Gain-Bandwidth
           Product

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      Authors: Yaqing Yu;Ming-Chun Tang;Da Yi;Dingmou Hong;Ting Shi;Richard W. Ziolkowski;
      Pages: 3153 - 3162
      Abstract: Extremely electrically small antennas (XESAs) exhibit low gain performance, which seriously limits their applications in space-constrained wireless platforms. We report an active transmitting XESA whose gain-bandwidth product (GBWP) exceeds the passive Bode-Fano upper bound. It is realized by incorporating a highly efficient, electrically small, near-field resonant parasitic (NFRP) antenna into the feedback loop of an operational amplifier (OpAmp). Rather than a cascaded configuration, the innovative structural embedding of the NFRP antenna directly with the OpAmp circuit significantly increases its effective gain without consuming any additional real estate. The operating mechanisms of the integrated system are explained with an equivalent circuit model. An optimized prototype was fabricated, assembled, and tested. The electrical size of its radiating element is extremely small with ka = 0.15 at 414 MHz, i.e., $a~approx lambda $ /42. The measured results of this active XESA, in good agreement with their simulated values, demonstrate that its effective gain can be dynamically tuned within a 6.01 dB range. The measured maximum effective gain and, hence, the effective isotropic radiated power (EIRP) witnesses a 9.152 dB (8.23 times) improvement in comparison to its passive counterpart and its measured GBWP surpasses the corresponding passive Bode-Fano upper bound by approximately 15.2 times.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • 3-D-Printed Shaped and Material-Optimized Lenses for Next-Generation
           Spaceborne Wind Scatterometer Weather Radars

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      Authors: Anastasios Papathanasopoulos;Jordan Budhu;Yahya Rahmat-Samii;Richard E. Hodges;Donald F. Ruffatto;
      Pages: 3163 - 3172
      Abstract: Current spaceborne wind scatterometers have shown failure due to mechanical wear from moving parts used to conically scan a directive beam. In order to eliminate the risk of mechanical rotation failure, an antenna design with no moving parts that achieve the conical beam sweep is desirable. In this article, a lightweight, 3-D-printed, inhomogeneous lens antenna is presented as an all-electronic alternative. Compared to the previous on-axis fed lenses, the real-life application requiring conical scanning necessitates significant developments regarding the synthesis, optimization, and prototyping of the off-axis fed lens. The lens antenna is designed using curved-ray geometrical optics coupled to particle swarm optimization to determine the optimum lens surface shapes and material inhomogeneity while obtaining a design with minimum volume and therefore mass. An 18 cm lens is designed using this approach. Instructions on how to 3-D-print the inhomogeneous lens are given using a unit cell design, which permits additive manufacturing using fused deposition modeling (FDM) techniques. The lens is measured for far-field pattern performance at various locations along with the ring-shaped focus of the azimuthally symmetric lens. The measurements agree well with predictions obtained by full-wave simulations. These all-electronic alternatives are expected to prolong the lifetime of future spaceborne wind scatterometers.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Analysis of Hemispherical Dielectric Resonator Antenna With an Imperfect
           Concentric Conductor

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      Authors: Mahesh Singh;Bratin Ghosh;Kamal Sarabandi;
      Pages: 3173 - 3182
      Abstract: This work presents a full-wave Green’s function approach for the rigorous investigation of a probe-coupled dielectric resonator antenna (DRA) configuration with an imperfect inner conductor. The impedance boundary condition is applied over the imperfect conductor in the formulation to derive the fields inside and outside the dielectric region, considering all higher-order modes. The technique enhances the applicability of the full-wave Green’s function in the evaluation of input impedance and radiation characteristics for an antenna structure with imperfectly conducting spherical surface, which to the best of our knowledge has not been reported before in the DRA literature. The role of the surface impedance on the antenna resonance and quality factor is thoroughly characterized. A suitable choice of the surface reactance depending on the radius of the imperfect conductor and dielectric-coating thickness enables the simultaneous reduction in the resonant frequency and quality factor for the antenna configuration. The effect of the surface reactance with varying coating permittivities is also investigated. The parametric variations in the input impedance, reflection coefficient, and antenna bandwidth with change in the surface impedance and coating permittivity for the antenna configuration are analyzed. The radiation characteristics for the antenna configuration are also examined.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • High-Gain Lens-Horn Antennas for Energy-Efficient 5G Millimeter-Wave
           Communication Infrastructure

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      Authors: Thomas A. H. Bressner;Martin N. Johansson;A. Bart Smolders;Ulf Johannsen;
      Pages: 3183 - 3194
      Abstract: Lower efficiencies of power amplifiers and increased path losses at higher frequencies are two reasons why utilizing millimeter-wave frequencies for future wireless communications is challenging. In this article, a high-gain multilens-horn antenna system is presented. The antenna system provides highly effective isotropic radiated power by using only a few high-gain antenna elements, where each element only needs a low transmit power of 26 dBm to reach users at far distances. Moreover, due to channel reciprocity, both down- and uplink benefit from an increased antenna gain. It is shown that a reasonable number of high-gain antennas can provide coverage in a 60° sector with an inter-site distance of 300 m. Based on radio-planning simulations, three horn shapes are identified to provide sufficient coverage. The final optimized dual-polarized multilens-horn design is fabricated and experimentally verified. With a low transmit power at the base station (BS) of 26 dBm, a signal strength of at least −65 dBm is achieved in 98.9% of the sector at 28 GHz under non-line-of-sight conditions for the vertical polarization. For the horizontal polarization, an area of 96.2% is covered.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Aperture-Shared Dual-Band Antennas With Partially Reflecting Surfaces for
           Base-Station Applications

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      Authors: Yue Qin;Ronglin Li;Quan Xue;Xiuyin Zhang;Yuehui Cui;
      Pages: 3195 - 3207
      Abstract: A new approach is proposed to develop aperture-shared dual-band antennas using partially reflecting surfaces (PRSs). A fully aperture-shared dual-band antenna consisting of a low-band antenna (LBA) and a high-band antenna (HBA) right below the LBA is first investigated. The aperture sharing has little influence on the LBA but causes a severe shielding effect on the HBA. To alleviate the shielding effect, a low-pass PRS is inserted between the LBA and HBA, forming an air-filled quasi-Fabry–Perot cavity, which can make compensation for the radiation from the HBA but with little influence on the LBA. The second PRS is introduced above the LBA to enhance the bandwidth (BW) for HBA. It is shown that the fully aperture-shared dual-band antenna achieves an impedance BW ( $vert text{S}11vert < -15$ dB) of ~43.7% (0.68–1.07 GHz) for the LBA and ~45% (1.7–2.7 GHz) for the HBA with an average gain of ~8 dBi and stable radiation patterns. Based on the PRSs, an aperture-shared dual-band antenna subarray is finally developed for base-station applications, which covers the frequency bands of 0.68–0.96 and 1.7–2.7 GHz for 2G/3G/4G mobile communications.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Archimedean Spiral Slotted Leaky-Wave Antenna

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      Authors: Xiaowen Li;Junhong Wang;Zheng Li;Yujian Li;Yunjie Geng;Meie Chen;Zhan Zhang;
      Pages: 3208 - 3222
      Abstract: In this work, a novel leaky-wave antenna (LWA) with Archimedean spiral slots is proposed for realizing high radiation efficiency and stable gain performance in both frequency-controlled and fixed-frequency beam-scanning applications. The structural feature of the proposed Archimedean spiral slot privileges LWA with properties of easy impedance matching and high leakage rate, because it avoids the strong reflection from large-size slots that commonly used in LWA design for high leakage rate. The bandwidths of the final designed Ka-band LWA defined by radiation efficiency larger than 90% and 80% are 13% and 25%, respectively, while the bandwidth defined by return loss less than −10 dB is 29%. And the gain fluctuations between different scanned beams are less than 2.4 dBi in the whole broadband. The LWA is further applied in designing a new-type antenna with double-layer substrate-integrated waveguide (SIW) structures, which has four feeding ports at the ends and a coupling plane in the middle interface and can realize the fixed-frequency beam switching between directions of −46°, −36°, 34°, and 45° at 28 GHz through changing the excitation port. The proposed LWAs are potential candidates for applying in future millimeter wave communication systems where multifunction integrated and multifrequency adaptive antennas are required.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • 28 GHz and 38 GHz Dual-Band Vertically Stacked Dipole Antennas on Flexible
           Liquid Crystal Polymer Substrates for Millimeter-Wave 5G Cellular Handsets
           

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      Authors: In-June Hwang;Ju-Ik Oh;Hye-Won Jo;Kwang-Seok Kim;Jong-Won Yu;Dong-Jin Lee;
      Pages: 3223 - 3236
      Abstract: Minimizing the size of mobile antennas is necessary for integrating the components inside a mobile device. Wideband and multiband antennas are also required to cover various 5G mobile communication frequency spectra. This article presents a vertically stacked dipole antenna array operating in the 28/38 GHz dual-band. The proposed antenna is small and satisfies the need for wide bandwidth in the form of a dual band. The antenna structure has symmetric 38 GHz band radiators positioned above and below a multilayer substrate, and a 28 GHz band radiator positioned on the middle plane, providing a dual-band antenna structure with small lateral width. Herein, two types of antenna structures are proposed, each with a single-ended and differential feed structure for compatibility with various RF front ends. The single antenna yields −10 dB bandwidth for return loss of 23.9% and 14.4%, and gain of 4.8 and 4.6 dBi at 28 and 38.5 GHz, respectively. The 4-element antenna array yields a gain of 9.0 dBi at 28 GHz and 10.3 dBi at 38.5 GHz. It was fabricated on a flexible substrate and can be bent and inserted into the lateral edge of the terminal. The proposed antenna elements and arrays satisfy the performance factors requisite for millimeter wave 5G communication including compact size, wideband, dual-band, and adequate gain.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Back-Fire to Forward Wide-Angle Beam Steering Leaky-Wave Antenna Based
           on SSPPs

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      Authors: Longfang Ye;Zhengyi Wang;Jianliang Zhuo;Feng Han;Weiwen Li;Qing Huo Liu;
      Pages: 3237 - 3247
      Abstract: We demonstrate an efficient back-fire to forward wide-angle beam steering leaky-wave antenna (LWA) based on a large dispersion gradient planar spoof surface plasmon polariton (SSPP) transmission line (TL) with split-ring units. To convert the highly confined SSPP waveguiding mode to a radiation mode, two arrays of metallic patches are periodically arranged on both sides of the SSPP TL. The patches are designed as two combined half-elliptical shapes to mitigate the open stopband effect and enhance the radiation performance. We propose a theoretical method to interpret the mechanism and predict the directional pattern of the LWA. To verify the proposed method, the SSPP TL and LWA prototypes are fabricated and measured. The calculation, simulation, and experimental results match well and show that the main beam of the LWA can steer a wide range of 112° from back-fire (−90°) to the forward quadrant of 22° passing through the broadside in 6.3–11 GHz, demonstrating a large scanning rate of 2.07°/%. Furthermore, the LWA also possesses the advantages of low profile, high average gain (12 dBi), high average efficiency (95%), and low sidelobe level (
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Input Admittance, Directivity, and Quality Factor of Biconical Antenna of
           Arbitrary Cone Angle

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      Authors: Ramakrishna Janaswamy;
      Pages: 3248 - 3258
      Abstract: New analytical expressions and numerical results for the mode coefficients, the directivity, and the quality factor and computationally convenient expressions for the input admittance of a symmetrical biconical antenna of arbitrary length $L$ and cone angle $theta _{0}$ are presented. The quality factor for a wide-angle biconical antenna is evaluated using three alternative formulations: 1) the evanescent energy stored outside the circumscribing sphere; 2) the total evanescent energy stored in all space; and 3) by equivalent circuit model, and these are all compared with Chu’s lower limit for an ideal antenna. Numerical calculations based on the analytical formula for antenna admittance confirm the conjecture that Foster’s reactance theorem remains invalid even for perfectly conducting antennas. Furthermore, the variation of directivity of a wide-angle biconical antenna is a slowly varying function of its electrical length and is shown to depart significantly from that of a thin cylindrical dipole. Finally, the ratio of directivity to $Q$ of an electrically small biconical antenna is shown to approach 78% of the value of an ideal omnidirectional antenna.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Tunable Filtering Antenna Based on Coaxial Cavity Resonators

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      Authors: Kai-Ran Xiang;Fu-Chang Chen;Qing-Xin Chu;
      Pages: 3259 - 3268
      Abstract: In this article, a method for designing a tunable coaxial filtering antenna is presented. The proposed filtering antenna has a simple structure, consisting of a standard waveguide and some metal cylinders. Instead of utilizing traditional coupling irises, an all-cylinder coupling structure is employed for flexible tuning. Thus, the center frequency and bandwidth of the coaxial filtering antenna can be conveniently tuned by adjusting the lengths of the cylinders. Theoretical analysis and design process of the filtering antenna are given in detail. A third-order tunable filtering antenna with Chebyshev response is designed to verify this method. The tunable range of the center frequency is from 9.25 to 10.75 GHz, and the tunable range of the fractional bandwidth (FBW) is from 2% to 8%. The measured gain of the antenna is flat and greater than 6.5 dBi along the tuning range. In addition, the antenna maintains good impedance and radiation characteristics throughout the tuning range.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • High-Impedance Surface-Based Null-Steering Antenna for Angle-of-Arrival
           Estimation

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      Authors: Jo Tamura;Hiroyuki Arai;Tatsuo Itoh;
      Pages: 3269 - 3276
      Abstract: A null-steering antenna with a high-impedance surface (HIS) to improve angle-of-arrival (AoA) estimation is designed and experimentally demonstrated. Because the HIS helps ensure that individual element patterns in an array are identical, the proposed antenna can perform null scanning with a low fluctuation without controlling the amplitude ratio of antenna elements. The simulation results demonstrate that the proposed antenna scans a null in the H-plane in 120° with greater than −30 dB from 2.4 to 2.6 GHz. Furthermore, both the measured S-parameters and element patterns agree well with the simulated results. Overall, the proposed antenna can successfully scan a null greater than −30 dB in 60° at a sampling frequency of 150 MHz.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Low-Profile Multifunctional Pattern Reconfigurable Antenna Using Periodic
           Capacitor-Loaded Surface for 5G and Beyond

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      Authors: Zhan Wang;Shuxuan Liu;Yuandan Dong;
      Pages: 3277 - 3286
      Abstract: This article describes a novel low-profile multifunctional pattern reconfigurable antenna using the periodic capacitor-loaded surface for 5G and beyond applications. A miniaturized periodic surface structure is first proposed using the shunt-loaded capacitor, which is studied by equivalent circuit models. A quarter-wavelength T-shaped director slot is etched on the edge of the ground, which leads to a tilted radiation pattern. By switching the ON-/OFF-states of p-i-n diodes embedded in the director slots, the main direction of the beam of the proposed antenna can be tuned among +35°, 0°, and −35°. To verify the design concept, a multifunctional pattern reconfigurable metamaterial-inspired antenna with a low profile of $0.05~lambda _{0}$ is fabricated and measured. The measured overlapping bandwidth for the eight radiation modes is 3.10–3.85 GHz (21.6%), well covering the 5G-N78 band. The port isolation between the two polarizations in eight modes is higher than 20 dB. The proposed reconfigurable metamaterial-inspired antenna shows the merits of low profile, wide bandwidth, high port isolation, low cost, multifunctional pattern reconfigurable capability, and easy fabrication for 5G and other sub-6 GHz applications.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Transformation-Optics-Based Flat Metamaterial Luneburg Lens Antenna With
           Zero Focal Length

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      Authors: Ruolei Xu;Zhi Ning Chen;
      Pages: 3287 - 3296
      Abstract: The transformation optics (TO) technique has been widely applied in the volume reduction of Luneburg lens (LL) in both optical and microwave regimes. However, it is found that the focus is usually not located on the surface of the transformed LL anymore after applying TO. The focus location shift results in a limited volume reduction, severe reflection from the new lens surface, and limited scanning range with increased spillover loss. This article theoretically studies and proposes a TO-based LL antenna with zero focal length by considering the phase mismatch caused by space discontinuity. The study first reveals that the transformation of an LL alone without sustaining the original boundary inherently deteriorates the original focusing property even before exerting any approximation. To validate the idea, a flat metamaterial LL antenna using TO is proposed, approximated, and fabricated using an integrated dielectric and conductive 3-D printing manufacturing process. The feeding patch antenna remains on the surface of the transformed lens. The thickness of the proposed antenna is reduced to 1/3 of a traditional LL in its boresight, while a ±20° beam scanning range is achieved with linearly shifted feedings. The study verifies that it is essential to ensure phase matching at the radiation boundary to maintain the original focusing property of an LL. The information derived from the study evidences the conditions of the enforcement of TO in electromagnetic problems such as dielectric lenses.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Bandpass Filter Prototype Inspired Filtering Patch Antenna/Array

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      Authors: Shuosheng Ji;Yuandan Dong;Yong Fan;
      Pages: 3297 - 3307
      Abstract: Planar filtering patch antenna and its related array inspired by a novel bandpass filter (BPF) prototype are proposed in this article. It is reasonable to replace the LC tank of a BPF prototype with a half-mode (HM) patch resonator with reference to their lumped circuits. That is, the HM patch would serve as a part of the BPF, as well as a radiator. This design method of implementing the filtering antenna is verified by a newly developed prototype. The physical model is realized in a simple form of a patch antenna fed by differential coupled lines. A microstrip-to-slotline transition is implemented to excite the coupled lines. Two radiation nulls beside the passband are obtained, thereby leading to a sharp band skirt. Based on this filtering antenna, a two-element patch array is designed. A CPW-to-slotline transition is designed to excite the united coupling lines, which serves as both a balun and a power divider. A high out-of-band rejection level within a wide stopband is achieved. For demonstration, the proposed filtering antenna and array are fabricated and measured. Reasonable agreement between the measured and simulated results is observed. Besides, the measured in-band gain of the filtering antenna array is over 10 dBi and flat, whereas the out-of-band rejection level is almost 30 dB.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Filtering Antenna Synthesis Based on Characteristic Mode Theory

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      Authors: Ke Li;Yan Shi;
      Pages: 3308 - 3319
      Abstract: This article developed a topology synthesis method based on characteristic mode theory (CMT) for the design of filtering antenna. The realization mechanism of radiation nulls of the antenna has been revisited and related to the characteristic fields and characteristic currents in the CMT. Two kinds of the methods based on the characteristic fields and the characteristic currents have been proposed to design the filtering antennas. Combined with the nondominated sorting genetic algorithm-II (NSGA-II), a CMT-based optimization procedure for the topology structure has been presented. With the proposed optimization algorithm, two filtering antennas without and with the consideration of the feeding port are designed, respectively, to achieve the radiation nulls at lower and upper band edges. For demonstration, the two proposed filtering antennas have been fabricated and measured. Good agreement between the simulated and measured results is observed to show the effectiveness of the proposed optimization design method for the topology structures with the filtering responses.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Near-Field Focusing Multibeam Geodesic Lens Antenna for Stable Aggregate
           Gain in Far-Field

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      Authors: Omar Orgeira;Germán León;Nelson J. G. Fonseca;Pedro Mongelos;Oscar Quevedo-Teruel;
      Pages: 3320 - 3328
      Abstract: The millimeter-wave band is a very attractive frequency band for the new generations of mobile cellular networks, i.e. 5G and 6G, due to its potential to support extremely high data rate transmissions. Innovative antenna solutions are needed to relieve the higher free space attenuation at these frequencies. Here, we propose a multibeam antenna based on a geodesic lens with stable aggregate gain characteristics in the far-field. An analytical model based on the physical path of the rays inside the lens is applied to achieve the field distribution in the aperture of the lens. This method is used to find the profile of a near-field focusing lens with a widened beam in the far-field. As a proof of concept, a seven-beam antenna has been designed. Due to the rotational symmetry of the geodesic lens, the antenna beams present similar characteristics over an extended sectorial coverage. The lens antenna has been manufactured, and its near-field focusing features were validated. The prototype has been assessed also in the far-field with a good agreement between model, simulations, and measurements. The main novelty of this prototype is to achieve a multiple beam coverage within $pm 67^circ $ in the H-plane and $pm 20^circ $ in the E-plane, with a gain roll-off smaller than 2 dB at 30 GHz and smaller than 3 dB at 35 GHz. These results validate the stable aggregate gain characteristics in the far-field of the proposed solution.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Pareto-Optimal Domino-Tiling of Orthogonal Polygon Phased Arrays

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      Authors: Paolo Rocca;Nicola Anselmi;Alessandro Polo;Andrea Massa;
      Pages: 3329 - 3342
      Abstract: The modular design of planar phased arrays (PAs) arranged on orthogonal polygon-shaped apertures is addressed and a new method is proposed to synthesize domino-tiled arrays fitting multiple, generally conflicting, requirements. Starting from an analytic procedure to check the domino-tileability of the aperture, two multi-objective optimization techniques are derived to efficiently and effectively deal with small and medium/large arrays depending on the values of the bounds for the cardinality of the solution space of the admissible clustered solutions. A set of representative numerical examples is reported to assess the effectiveness of the proposed synthesis approach also through full-wave simulations when considering nonideal models for the radiating elements of the array.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • High-Efficiency Ka-Band Circularly Polarized Radial-Line Slot Array
           Antenna on a Bed of Nails

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      Authors: Jose I. Herranz-Herruzo;Alejandro Valero-Nogueira;Miguel Ferrando-Rocher;Bernardo Bernardo-Clemente;
      Pages: 3343 - 3353
      Abstract: Radial-line slot-array antennas (RLSAs) provide an extremely simple solution to achieve high-gain circularly polarized radiation patterns without the need for complicated feeding networks or polarizers. The dielectric-filled radial waveguide, however, drastically reduces the efficiency that is potentially achievable by RLSA antennas at millimeter waveband. In this article, a novel architecture for an all-metal RLSA is proposed by replacing the dielectric material with a regular bed of metallic nails, thus maintaining the required slow wave characteristic within the radial waveguide. The slot array is efficiently optimized by using an ad hoc method-of-moments solver, based on the definition of an equivalent problem in the waveguide region. This accurate optimization process, along with the all-metal nature of the antenna, allows to reach a measured peak total efficiency above 80% at 30 GHz. The fabricated prototype consists of two pieces: the bottom waveguide with the bed of nails and the top slotted plate, which are easily assembled by means of a few screws. Experimental results report a peak gain of 35.0 dBi for a radiation efficiency of 94%, and a wideband matching performance with a very pure axial ratio, below 0.6 dB.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Single-Layer Dual-Band Array at Low-Frequency Ratio With Concurrent
           Broad Fan Beam and Narrow Pencil Beam

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      Authors: Mei Li;Lin Pu;Ming-Chun Tang;Lei Zhu;
      Pages: 3354 - 3365
      Abstract: A single-layer, dual-band, shared-aperture array with a broad fan beam in the lower band centered at 5 GHz and a narrow pencil beam in the adjacent upper band centered at 5.8 GHz is presented in this article. First, the schematic of a dual-band array with its beamwidth regulation capability is presented. Then, two key components, i.e., a novel dual-band patch antenna element and a compact filtering phase shifter (FPS) are developed. The antenna element has counterintuitive beam patterns with broad azimuthal half-power beamwidth (HPBW) of 183.3° in the lower band but much narrower azimuthal HPBW of 68.5° in the upper band, indicating its excellent ability in beamwidth regulation with a figure of merit (FoM) of 2.31. Meanwhile, the FPS serves as a band-stop filter in the lower band and a phase shifter in the upper band. Furthermore, a two-element series-fed subarray is designed by cascading two properly designed antenna elements through the FPS. Finally, a parallel-series-fed array consisting of four rows of the series-fed subarrays is implemented, and a prototype is fabricated and tested. The measured results, in good agreement with the simulated ones, have demonstrated that the array satisfactorily attains a broad fan beam with azimuthal HPBW of 156° and gain of 11.05 dBi at 5 GHz and a narrow pencil beam with azimuthal HPBW of 30° and gain of 16.23 dBi at 5.8 GHz under a shared aperture of $1.37lambda _{0} times 3.53lambda _{0} times 0.05lambda _{0}$ , indicating an enhanced FoM up to 4.48. The FoM and gain could be further improved by simply expanding the array’s dimension based on the developed array topology.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Reactive Impedance Surface-Loaded Wideband Wide-Scanning Phased Array in
           Triangular Lattice

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      Authors: Binyun Yan;Liangyu Sun;Weixing Sheng;Zhi Ning Chen;
      Pages: 3366 - 3373
      Abstract: A phased array loaded with a reactive impedance surface (RIS) is proposed for wideband wide-scanning performance. The mushroom-like RIS structure, etched on the same printed circuit board (PCB) of the antenna, is introduced as a superstrate over the antenna aperture. The reactance of the RIS structure compensates for the scan impedance variation of the antenna during the beam scanning, explained by the equivalent transmission-line model. A superior scanning performance in all azimuth planes is achieved, and the scan blindness in the H-plane is alleviated, especially. The total compact design is capable of operating over a 2.3:1 (6 –14 GHz) bandwidth in broadside and over a 1.8:1 bandwidth in ±60° E-plane, ±70° D-plane, and ±65° H-plane scanning. The array is implemented in a triangular lattice, and edge elements in the E-plane are connected to metal walls for edge effect elimination. A 45-element ( $5times 9$ ) array prototype is fabricated and measured. Active reflection coefficients are calculated, and scanning patterns are synthesized.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Multi-User Near-Field Focusing Through Time-Modulated Arrays

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      Authors: Rafael González Ayestarán;Marcos Rodriguez Pino;Paolo Nepa;Borja Imaz-Lueje;
      Pages: 3374 - 3384
      Abstract: The feasibility of a novel near-field (NF) focusing technique based on time-modulated arrays (TMAs) is studied. The formulation for an NF transmission problem is developed, showing its interesting potential for multiuser focusing at different frequencies, advantageously exploiting the characteristic TMA side frequencies radiation. Although asking for specific patterns at a set of different radiation frequencies may degrade the overall system performance, it is shown that the required radiated field distributions may still be achieved with acceptable focusing performance. This fact makes TMAs an interesting alternative to other technologies due to their simpler implementation through digital devices and also allowing for an adaptive implementation as required for many real applications. Some illustrative examples are presented.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Nested Optimization for the Synthesis of Asymmetric Shaped Beam Patterns
           in Subarrayed Linear Antenna Arrays

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      Authors: Paolo Rocca;Lorenzo Poli;Nicola Anselmi;Andrea Massa;
      Pages: 3385 - 3397
      Abstract: In this article, a novel clustering method for synthesizing asymmetric shaped beam patterns in subarrayed linear antenna arrays is presented. The definition of the elements aggregations along with the corresponding weighting coefficients is accomplished through two nested iterative loops. An external loop is aimed at determining the optimal excitations of a reference fully populated array that fits user-defined pattern masks, while the internal one is devoted to the synthesis of the best subarrayed layout affording the closest pattern to the reference one by means of a ${k}$ -means-based algorithm that minimizes the total intracluster variations. Representative numerical results are presented and compared with competitive state-of-the-art solutions to assess the effectiveness of the proposed synthesis method.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A mm-Wave Phased-Array Fed Torus Reflector Antenna With ±30° Scan Range
           for Massive-MIMO Base-Station Applications

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      Authors: Amr Elsakka;Amirashkan Farsaei;A. J. van den Biggelaar;Adrianus Cornelis Franciscus Reniers;Martin N. Johansson;Rob Maaskant;Ulf Johannsen;Oleg A. Iupikov;A. Bart Smolders;Marianna V. Ivashina;
      Pages: 3398 - 3410
      Abstract: A phased-array fed reflector antenna system is presented which can be used for mm-wave base station applications. The proposed system is designed to support massive-multi-input–multi-output (MIMO) scenarios within a wide coverage ( $pm 30^circ $ ) in the azimuth plane and a limited coverage at the elevation plane. A design and characterization methodology has been established to optimize the system for the operation in various line-of-sight conditions by adopting the maximum-ratio-transmission (MRT) and zero-forcing (ZF) MIMO algorithms. A two-user MIMO case study has been considered for the evaluation of the key system performance metrics, i.e., the effective isotropic radiated power, power consumption, signal-to-noise-ratio (SNR), and signal-to-interference-plus-noise-ratio (SINR). This study demonstrates that the phased-array fed reflector concept has a major advantage over traditional direct-radiating phased-array (DRPA) antennas to reduce energy consumption. In the present example, it requires 12–14 dB less transmitted power as compared with the MRT-beamformed DRPAs for the same SNR, and 26–27 dB less transmitted power relatively to ZF-beamformed DRPA systems for the same SINR. A prototype, employing a 55 cm diameter torus reflector and operating at 28 GHz-band, has been manufactured and tested. The measurement results agree well with simulations.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • In-Band Scattering Cancellation Techniques for Vivaldi Antenna Array

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      Authors: Zhiyuan Liu;Yikai Chen;Shiwen Yang;
      Pages: 3411 - 3420
      Abstract: Vivaldi antenna array is extremely suitable for airborne installed phased array developments because of its wide bandwidth and wide scanning angle. Despite its great potential, the usage of the Vivaldi antenna array is still limited by its 3-D structure, which will probably produce large electromagnetic scattering and destroy the stealth property of the airborne platform. In this work, two techniques are developed to reduce the in-band scattering of Vivaldi antenna arrays. First, a novel Vivaldi antenna element with an inherent low scattering level is proposed based on the extraction of the scattering and radiating currents. Second, a chessboard artificial magnetic conductor (AMC) surface with a 180° reflection phase difference is developed to cancel out the scattering caused by the antenna array. Due to the two techniques, an average of 5–10 dB in-band monostatic scattering reduction is realized, while the radiation performance of the 6–18 GHz Vivaldi phased array with a ±60° scanning range in the E-/H-planes is preserved. Finally, the prototypes of the proposed $8 times 8$ Vivaldi phased array and a reference array are fabricated and measured to demonstrate the effectiveness of the in-band scattering techniques for both normal and oblique incident waves with HH/VV polarized scattering.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Shaped-Beam Pattern Synthesis With Sidelobe Level Minimization via
           Nonuniformly-Spaced Sub-Array

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      Authors: Zhipeng Lin;Haoquan Hu;Bo Chen;Shiwen Lei;Jing Tian;Yin Gao;
      Pages: 3421 - 3436
      Abstract: This article deals with the low-sidelobe shaped-beam pattern synthesis (SBPS) problem using two nonuniformly spaced subarray configurations, including amplitude and amplitude–phase subarray configurations. An optimization model is proposed for the SBPS problem to minimize the peak sidelobe level by jointly optimizing the subarray configuration and element excitations/positions. A typical advantage of the proposed model is to reduce the system control points while maintaining the benign array performance. However, the formulated problem is a mixed-integer nonconvex one, which makes it challenging. Besides, this problem cannot be directly solved due to the existence of coupling optimization variables. Thus, a set of auxiliary variables is introduced to move the coupling optimization variables into equality constraints. These equality constraints are converted into quadratic penalty forms and are added to the objective function. Then, an efficient iterative algorithm is proposed using the penalty-based optimization method, which solves the original problem by iteratively solving a series of subproblems based on the inexact block coordinate descent technique. Numerical examples with different beam patterns are performed to verify the effectiveness of the proposed algorithm.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Wideband Beampattern Synthesis Using Single Digital Beamformer With
           Integer Time Delay Filters

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      Authors: Qinghui Lu;Guolong Cui;Ruitao Liu;Xianxiang Yu;Xiangrong Wang;Lingjiang Kong;
      Pages: 3437 - 3449
      Abstract: Existing wideband beampattern synthesis methods usually require multiple beamformers, each corresponding to one frequency bin, which results in excessive resource consumption in engineering practice. To alleviate the resource consumption of wideband array beamforming, we propose a novel time-domain wideband digital beamformer that can control the beam shape over the whole bandwidth for interference mitigation by using only one set of amplitude–phase weights and integer time delay filters. To tackle the resultant optimization problem, two effective algorithms are introduced, and both can solve the problem within polynomial time. One is an alternating optimization algorithm that decomposes the original problem into multiple tractable subproblems iteratively. The other is the convex approximation algorithm that transforms the original problem into a series of second-order cone programming problems iteratively. The two algorithms exhibit their respective advantages in terms of convergence and computational complexity. Extensive numerical examples are presented to evaluate the proposed time-domain wideband beamforming strategy, highlighting that it can form a deep notch in any interested spatial–spectral region to suppress the strong interferences.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Fundamental Equations of Electromagnetics Using Field-Impulses as Physical
           Field-Integrators

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      Authors: Eng Leong Tan;
      Pages: 3450 - 3458
      Abstract: As signified by the well-known Aharanov–Bohm effect, the fields only under-describe electromagnetics and are thus not sufficient, while the potentials over-describe electromagnetics and are more than necessary with gauge redundancy. In lieu of the traditional fields and potentials, this article presents new formulations that introduce from the outset the concept and utilization of field-impulses for the fundamental equations of electromagnetics. Unlike the potentials that may or may not be real or causal depending on the gauge, the field-impulses as physical field-integrators (time-integrals) are like fields being physically real, causal, and gauge-independent. Furthermore, the single electric field-impulse/integrator alone through its second-order (wave) equation is capable of aptly describing electromagnetics in all cases of electrostatics, magnetostatics, and electrodynamics. Upon close scrutiny and comparison, the optional static–dynamic decomposition of electric field-impulse can be related to the potentials with source-incorporated gauge condition. Such source-incorporated condition is unlike other popular gauge conditions that are source-free or incorporating the source implicitly. The electric field-impulse as physical field-integrator is necessary and sufficient for many aspects of electromagnetics including field derivation, Lorentz force, momentum, interaction energy, quantum particle–electromagnetic interactions, etc.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Highly Selective Frequency Selective Surface With Ultrawideband Rejection

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      Authors: Tao Hong;Shuai Guo;Wen Jiang;Shuxi Gong;
      Pages: 3459 - 3468
      Abstract: Frequency selective surface (FSS) with ultrawide out-of-band rejection is proposed in this article. For achieving an ultrawide and high-intensity stopband, a common second-order bandpass FSS is designed and then improved by an equivalent circuit model (ECM) design. The hybrid resonator pole separation (HRPS) decoupling method is proposed and applied during the design process. The modified ECM could realize the suppress effect on the unexcepted out-of-band transmission pole caused by coupling between layers and achieve the desired ultrawideband rejection. Furthermore, the corresponding FSS structure is established from the modified ECM through the mapping method. In addition, we conducted a detailed analysis of equivalent circuit design and the required frequency response achieve method. The measured results show that a second-order passband from 3.12 to 4.64 GHz with 0.3 dB insertion loss (IL) in the band is obtained by the proposed FSS. Meanwhile, transition bands from the passband to the stopband are narrow, and the transmission coefficients out of the passband could be suppressed under −20 dB from 5.5 to over 40 GHz. All the results demonstrate that the proposed FSS can realize an excellent out-of-band rejection while maintaining a well passband.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Radiation Properties of Pure Magnetic Dipole Antenna With Spherical
           Current Density via Exact Maxwell Solution

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      Authors: David Alan Garren;
      Pages: 3469 - 3476
      Abstract: A recent analysis has investigated a possible new type of magnetic antenna that is characterized by an electric current that flows azimuthally on the surface of a sphere with a density magnitude that scales as the sine function applied to the spherical polar angle. This analytic theory has yielded an exact solution of the Maxwell equations for the electromagnetic (EM) fields of the resulting radiation for all spatial regions, including that both interior and exterior to the spherical current shell. In the present investigation, the EM fields are expressed in terms of an alternative, and perhaps more intuitive, form such that the radial dependence varies as a product of polynomial and exponential functions. In addition, the subject spherical current density is shown to produce exactly the same purely dipole radiation fields exterior to the spherical current shell as that of an infinitely small magnetic dipole moment antenna. Furthermore, the present analysis calculates various radiation properties corresponding to the subject spherical current antenna concept, including the Poynting vector, radiation impedance, quality factor, and maximum effective area. Finally, the present investigation reveals that the subject spherical electric current density achieves the minimum quality factor that can be attained for all antennas.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Optimization of Electromagnetic Metasurface Parameters Satisfying
           Far-Field Criteria

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      Authors: Stewart Pearson;Sean Victor Hum;
      Pages: 3477 - 3488
      Abstract: Electromagnetic metasurfaces offer the capability to realize arbitrary power-conserving field transformations. These field transformations are governed by the generalized sheet transition conditions, which relate the tangential fields on each side of the surface through the surface parameters. Ideally, designers would solve for the surface parameters based on their application-specific far-field criteria. However, determining the surface parameters for these criteria is challenging without knowledge of the tangential fields on each side of the surface, which are not unique for a given far-field pattern. Current designs are generally restricted to analytical examples where the tangential fields can be solved for, or determined via ad hoc methods, although there has been recent work to circumvent this. This article presents an optimization scheme, which determines surface parameters, such as electric impedance, magnetic admittance, and magnetoelectric coupling, satisfying far-field constraints, such as beam level, sidelobe level, and null locations. The optimization is performed using a method of moments-based model incorporating edge effects and mutual coupling. The surface parameters are optimized for using the alternating direction method of multipliers. Examples of this optimization scheme performing multicriteria pattern forming, extreme angle small surface refraction, and Chebyshev-like beamforming are presented.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Impact of Power Spectrum in Geometrical Coding on the Scattering of Random
           Electromagnetic Coding Metasurface

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      Authors: Xujin Yuan;Hao Zhou;Xiuzhu Ye;Rui Zhang;Mingji Chen;Xiaoyu Zhang;Weiduan Li;Xu Chen;Linling Li;Yixing Huang;Guangyuan Wang;Daining Fang;
      Pages: 3489 - 3494
      Abstract: The mechanism of reflective electromagnetic metasurfaces has potential applications in information transfer and electromagnetic scattering suppression. In this article, the relation between the geometric entropy of the electromagnetic metasurface pattern and the scattering entropy of the metasurface is studied by introducing the power spectrum in the coding sequence generation, considering the correlation nature in the initial random geometric coding. The geometric entropy is found to generate an impact on the scattering form and scattering entropy of the 2 bit order random coding. The 2-D wideband power spectrum with central sunken is found to form the highest entropy in the scattering pattern. A metasurface sample is designed, prepared, and measured in the experiment to validate this theory. The results indicate another possible control parameter in entropy modulation, which has potential uses in multibeamforming and information transfer techniques.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Inverse Design of Multi-Input Multi-Output 2-D Metastructured Devices

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      Authors: Luke Szymanski;Gurkan Gok;Anthony Grbic;
      Pages: 3495 - 3505
      Abstract: In this work, an optimization-based inverse-design method is provided for multi-input–multioutput (MIMO) metastructured devices. Typically, optimization-based methods use a full-wave solver in conjunction with an optimization routine to design devices. Due to the computational cost, this approach is not practical for designing electrically large aperiodic metastructured devices. To address this issue, a 2-D circuit network solver using reduced-order models of the metastructure’s unit cells is introduced. The circuit network solver is used in conjunction with a gradient-based optimization routine that uses the adjoint variable method to solve large-scale optimization problems such as those posed by metastructured devices. To validate the inverse-design method, a planar beamformer and an analog signal processor for aperture field reconstruction are designed and validated with full-wave simulations.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Chiral Absorber-Based Frequency Selective Rasorber With Identical
           Filtering Characteristics for Distinct Polarizations

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      Authors: Weipeng Wan;Yongfeng Li;He Wang;Zhibiao Zhu;Yang Cheng;Lixin Jiang;Lin Zheng;Jiafu Wang;Shaobo Qu;
      Pages: 3506 - 3514
      Abstract: In this article, we propose a new paradigm to design frequency-selective rasorber (FSR) with two-sided efficient absorptions and broadband transmission in a chiral structure. The proposed FSR is implemented via combining two chiral absorber layers with a bandpass frequency-selective surface (FSS). An absorptive split-ring resonator (ASRR) inserted with a resistive film is designed to provide efficient spin-sensitive absorption. Then, four ASRRs are arranged to form a $C_{4}$ symmetric split-ring absorber (SRA) with identical absorption for distinct polarized incident waves. The physical mechanisms of spin-selective absorption and polarization-insensitive absorption are discussed theoretically. The broadband bandpass FSS is introduced to provide a transparent window and ground plane for the absorbers. A prototype is fabricated and measured to verify the feasibility of the method. The simulation and experimental results manifest over 90% absorptive bands of 1.5–3.6 and 15.2–21.6 GHz and a transmission band of 8–12 GHz with insertion loss less than 2 dB. Compared with previous FSRs, the proposed FSR has a broadband transmission, efficient absorptions with high-frequency selectivity, and easy geometric structure.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Eigenmode-BLT-Based Method for Calculating the Coupling to Microstrip
           Antenna Inside a Cavity

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      Authors: Pei Xiao;Jiawei Li;Jinxin Li;Yongfeng Qiu;Zhu Liu;Chao Zhang;Gaosheng Li;William T. Joines;
      Pages: 3515 - 3522
      Abstract: The electromagnetic (EM) coupling effects of microstrip antennas have become increasingly prominent in complicated electric systems. In this article, a hybrid method is proposed based on the combination of cavity eigenmode theory and BLT equation. First, the internal electric field generated by the transmission lines inside the resonant cavity is obtained via cavity eigenmode theory. Then, the coupling mechanism between the electric field and microstrip antenna is established through radiation coupling interference. On this basis, the BLT equation and numerical integration method are applied to determine the induced voltage at the target microstrip antenna. Eventually, the proposed approach is validated by a full-wave simulation method and the impact of the microstrip antenna parameters on the coupling interference is discussed. This article provides an analytical method for calculating the coupling of a microstrip antenna. Compared with numerical simulation, this method has certain potential advantages in solving closed electrically large objects. Furthermore, duplicate modeling can be avoided in the same type of scenario.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Evaluation of 6-D Reaction Integrals via Double Application of the
           Divergence Theorem

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      Authors: Javier Rivero;Francesca Vipiana;Donald R. Wilton;William A. Johnson;
      Pages: 3523 - 3537
      Abstract: This article addresses the problem of efficiently and accurately evaluating the singular or near-singular double volume (6-D) reaction integrals fundamental to the solution of volume integral equations (VIEs) using the method of moments (MoM). VIE techniques based on the MoM are used to obtain accurate solutions for electromagnetic (EM) problems of all types, and the accurate computation of the singular and near-singular reaction integrals that occur in the resulting system matrices is crucial for accurate EM modeling. Here we propose a scheme to treat, as a whole, the 6-D reaction integrals appearing in the MoM. The divergence theorem is directly applied twice in the physical space domain, not a transformed domain, thus eliminating restrictions to well-shaped elements. With appropriate integration reordering, the 6-D volume integrals are expressed as two radial integrals followed by two surface integrals over source and observation domain boundaries. We further smooth the integral by removing the static form of the kernel and evaluating it separately using a semi-analytical approach. The method is numerically validated for static and dynamic kernels arising in the electric field VIEs (i.e., for kernels having $1/R$ singularities) and for linear basis functions.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Comparison of CBFM-Enhanced Iterative Methods for MoM-Based Finite Antenna
           Array Analysis

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      Authors: Tomislav Marinović;Rob Maaskant;Raj Mittra;Guy A. E. Vandenbosch;
      Pages: 3538 - 3548
      Abstract: In this article, we compare different iterative techniques enhanced by the CBFM, which are used to analyze finite arrays of disjoint antenna elements. These are based on the stationary-type methods (Jacobi, Gauss–Seidel, and macroblock Jacobi), the nonstationary GMRES, and the hybrid alternating GMRES-Jacobi (AGJ) method that combines these two types. In each iteration, the reduced CBFM system is constructed based on the previous iterates, the solution of which is used to update the solution vector in the next iteration with improved accuracy. In this way, the convergence of the classical iterative techniques can be greatly improved. The convergence rates and computational costs of the CBFM-enhanced iterative methods are analyzed by considering several MoM-based problems. The GMRES-based method, which employs the block-Jacobi preconditioner, outperforms the other methods when the MoM matrix is ill-conditioned. For well-conditioned MoM matrices with reduced diagonal dominance due to the increased presence of the interelement coupling effects, the AGJ method or the methods based on the stationary-type iterations may require smaller computational effort to converge to the desired solution accuracy in comparison to the GMRES-based approach.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Butterfly-Accelerated Volume Integral Equation Solver for Broad
           Permittivity and Large-Scale Electromagnetic Analysis

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      Authors: Sadeed Bin Sayed;Yang Liu;Luis J. Gomez;Abdulkadir C. Yucel;
      Pages: 3549 - 3559
      Abstract: A butterfly-accelerated volume integral equation (VIE) solver is proposed for fast and accurate electromagnetic (EM) analysis of scattering from heterogeneous objects. The proposed solver leverages the hierarchical off-diagonal butterfly (HOD-BF) scheme to construct the system matrix and obtain its approximate inverse, used as a preconditioner. Complexity analysis and numerical experiments validate the $O(Nlog ^{2}N)$ construction cost of the HOD-BF-compressed system matrix and $O(N^{1.5}log N)$ inversion cost for the preconditioner, where $N$ is the number of unknowns in the high-frequency EM scattering problem. For many practical scenarios, the proposed VIE solver requires less memory and computational time to construct the system matrix and obtain its approximate inverse compared to a $mathcal {H}$ matrix-accelerated VIE solver. The accuracy and efficiency of the proposed solver have been demonstrated via its application to the EM analysis of large-scale canonical and real-world structures comprising of broad permittivity values and involving millions of unknowns.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Method of Moments and T-Matrix Hybrid

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      Authors: Vit Losenicky;Lukas Jelinek;Miloslav Capek;Mats Gustafsson;
      Pages: 3560 - 3574
      Abstract: Hybrid computational schemes combining the advantages of a method of moments formulation of a field integral equation and T-matrix method are developed in this article. The hybrid methods are particularly efficient when describing the interaction of electrically small complex objects and electrically large objects of canonical shapes such as spherical multilayered bodies where the T-matrix method is reduced to the Mie series making the method an interesting alternative in the design of implantable antennas or exposure evaluations. Method performance is tested on a spherical multilayer model of the human head. Along with the hybrid method, an evaluation of the transition matrix of an arbitrarily shaped object is presented and the characteristic mode decomposition is performed, exhibiting fourfold numerical precision compared to conventional approaches.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Simplified Discontinuous Galerkin Self-Dual Integral Equation
           Formulation for Electromagnetic Scattering From Extremely Large IBC
           Objects

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      Authors: Xiao-Wei Huang;Ming-Lin Yang;Xin-Qing Sheng;
      Pages: 3575 - 3586
      Abstract: The mechanism of each term in the discontinuous Galerkin (DG) method is analyzed and studied numerically. A simplified DG self-dual integral equation (SDIE) formulation is proposed for solving electromagnetic scattering from large-scale objects with impedance boundary condition (IBC). Numerical results show that the proposed formulation is more flexible and memory saving than the conventional DG formulations, especially for implementing the multilevel fast multipole algorithm (MLFMA). Moreover, a massively parallel strategy of the MLFMA is employed to further strengthen its capability for electrically large problems. Numerical experiments demonstrate the accuracy and efficiency of the proposed formulation for analyzing electromagnetic scattering problems of IBC objects with billions of unknowns.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Stochastic Method of Moments (SMoM) Analysis of Wire Antenna Arrays With
           Random Elements Locations

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      Authors: Amirali Hatamkhani;Reza Faraji-Dana;
      Pages: 3587 - 3594
      Abstract: In this article, we propose a full-wave numerical approach called stochastic method of moments (SMoM), for analyzing the effects of uncertainties in the locations of elements in a random antenna array on its performance characteristics. Using SMoM with subdomain basis functions converts the governing mixed potential integral equation to a matrix equation consisting of closed-form functions in terms of the random parameters. We then apply MacLaurin’s series expansions on the derived matrix equation to find the stochastic current distributions on the array elements with controllable accuracy using different orders of MacLaurin’s series. In this way, the mean values and standard deviations of the current distributions of array elements, and their other performance characteristics can be determined easily. The proposed method enjoys fast computation as well as controllable accuracy, and its results are compared with those obtained by the Monte Carlo method for verification.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Method of Moments Wide Band Adaptive Rational Interpolation Method for
           High-Quality Factor Resonant Cavities

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      Authors: Hao-Bo Yuan;Wen-Tao Bao;Chung Hyun Lee;Brian F. Zinser;Salvatore Campione;Jin-Fa Lee;
      Pages: 3595 - 3604
      Abstract: A new adaptive rational interpolation method is proposed to obtain the wideband frequency response of a resonant cavity simulated with the method of moments (MoM). This interpolation method uses both the Loewner matrix to construct a rational expression for the solution vector of MoM’s matrix system and an error estimator generated by the solution vectors and their derivatives. This error estimator is implemented in the adaptive procedure to gain a minimum set of frequencies and solution vectors required in the interpolation. The resulting set of frequencies and solution vectors is applied to interpolate other system variables, such as shielding effectiveness and input impedance. Numerical results of a slotted cylindrical cavity supporting high-quality factor resonances are presented, showing that the new rational interpolation method is accurate and efficient in interpolating the complicated resonant response of the solution vector functions.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Gaussian Beam Propagators Scattering by a Fast Moving PEC Wedge

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      Authors: Ram Tuvi;Timor Melamed;
      Pages: 3605 - 3612
      Abstract: We are concerned with the scattering of 3-D Gaussian beam propagators from a perfectly electric conductor wedge in uniform translation. The incident Gaussian beam propagators are the building blocks of the phase-space beam summation method, which is a general framework for analyzing the propagation and scattering of waves. In this article, we use the asymptotic plane wave (PW) scattering from a moving wedge. By applying asymptotic analysis to the PW decomposition of the incident fields, we obtain the closed-form expressions for the wave potentials and the corresponding time-dependent electromagnetic vector operators. The asymptotic scattered potentials consist of relativistic reflected, shadowing, and diffraction waves. These waves are investigated and parameterized to include the velocity-dependent features and wave phenomena corresponding to the wedge speed. Numerical examples are included.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • On the Formulation and Implementation of the Love’s Condition Constraint
           for the Source Reconstruction Method

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      Authors: Mario Phaneuf;Puyan Mojabi;
      Pages: 3613 - 3627
      Abstract: The formulation and implementation of the Love’s condition constraint for the source reconstruction method (SRM) in near-field antenna measurements are analyzed in the context of inverse problems. To this end, the SRM is first analyzed to identify the nonunique or nonradiating (NR) current sources which may be present. Next, the advantages and disadvantages of general regularization techniques, which may address the NR currents, are presented which serve to motivate the use of the Love’s condition constraint. The main methods of formulating the constraint are then presented, one of which is a novel technique developed for this article. Following this, the formulation methods are analyzed in order to predict the similarities and differences of the methods in the context of addressing the NR currents of the SRM. This analysis is reinforced by simulated antenna measurements. In particular, the novel formulation method is demonstrated to provide a greater regularizing effect (in the examples considered), at the cost of computational complexity.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Work-Energy Principle Based Characteristic Mode Theory With Solution
           Domain Compression for Metal-Material Composite Scattering Systems

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      Authors: Ren-Zun Lian;Xing-Yue Guo;Ming-Yao Xia;
      Pages: 3628 - 3642
      Abstract: This article focuses on further improving the characteristic mode theory (CMT) for metal-material composite scattering objects. The improved CMT is alternatively established in a novel work-energy principle (WEP) framework. Under the WEP framework, a novel driving power operator (DPO) is introduced as the generating operator for characteristic modes (CMs). Then, a novel diagonalizing DPO method is proposed to construct the CMs. In addition, a novel solution domain compression (SDC) scheme is developed to suppress spurious modes. Compared with the conventional integral equation (IE) framework, the novel WEP framework more clearly reveals the core physical feature of CMs, and then easily derives the famous Parseval’s identity. Compared with the conventional impedance matrix operator (IMO), the novel DPO is more advantageous in the aspect of distinguishing independent variables from dependent variables, and has a smaller computational burden, and has a more acceptable numerical performance in the aspect of calculating CMs. Compared with the conventional dependent variable elimination (DVE) scheme, the novel SDC scheme is equally effective in the aspect of suppressing spurious mode, and reconfirms the same conclusion that the spurious modes result from ignoring the dependence relationships among the currents contained in DPO.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Resolution Enhancement for Mixed Boundary Conditions in Inverse Scattering
           Problems

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      Authors: Fan Yin;Chang Chen;Weidong Chen;
      Pages: 3643 - 3655
      Abstract: In the mixed boundary inverse scattering problem (ISP), conducting and dielectric scatterers coexist in the same region, which challenges the present quantitative inverse scattering methods. Moreover, to ensure the incident waves penetrating the lossy or high-contrast objects, lower wavelength is applied in most inverse scattering applications. Therefore, methods with wavelength or subwavelength resolution are required for the mixed boundary ISP. In this article, we devise a quantitative inversion scheme alternately updating the contrast of dielectric scatterers and the T-matrix of conducting scatterers. The proposed alternate parameter updating method (APUM) avoids the reconstruction deterioration from both the large imaginary parts of conducting contrasts and the limited expansion order of the T-matrix. Then, we further improve the resolution of the APUM by optimizing the incident fields, which is also a regularization strategy. In particular, we design superoscillatory incident fields to quantitatively converse the high spatial spectrum of objects into low spectrum contrast sources, which can retain the high-frequency information of objects in the low-passband of the Green function. The results with synthetic data and single-frequency Fresnel experimental data verify the effectiveness of the proposed method.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Precise RCS Extrapolation via Nearfield 3-D Imaging With Adaptive
           Parameter Optimization Bayesian Learning

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      Authors: Ling Pu;Xiaoling Zhang;Jun Shi;Shunjun Wei;Tianwen Zhang;Xu Zhan;
      Pages: 3656 - 3671
      Abstract: Nearfield (NF) 3-D imaging provides an effective solution of objects’ radar cross section (RCS) within a compact range. This article proposes a precise RCS extrapolation via NF 3-D imaging with adaptive parameter optimization Bayesian learning (APOBL), i.e., first, in the process of NF 3-D imaging, objects’ scattering centers may vary with the observation angle, while it is hard for the existing Bayesian learning via presetting parameters to reach an optimal estimation. For this issue, we present a parameter self-adaption solution, improving precision, and stability. Second, we also apply a block-based optimization idea in Bayesian-learning-based 3-D imaging, ensuring NF 3-D imaging quality. Third, in the process of RCS extrapolation, we apply a weighted Green’s function operator into the 3-D imaging-based NF-to-far-field (NF–FF) compensation, further ensuring high precision. The simulation and experiment results verify that the proposed method has an advantage in precision over the existing 3-D imaging-based RCS extrapolation methods.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Object Detection of Ground-Penetrating Radar in the Frequency Domain Using
           Three-Antenna System

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      Authors: Chainarong Kittiyanpunya;Monai Krairiksh;
      Pages: 3672 - 3679
      Abstract: An object detection method of ground-penetrating radar (GPR) in the frequency domain using three-antenna system is proposed in this study. The presented methodology utilizes the electromagnetic (EM) scattering from the object for identification using its natural poles. Two schemes of GPR system were examined. The first scheme was the conventional GPR comprising one transmitter and one receiver. The second scheme comprises two transmitters and one receiver, which the transmitters were excited by out-of-phase generators with each other. The simulations were initially performed using the three-antenna system for GPR. The results indicated that the natural poles in the scattering responses changed according to the characteristics of the object. For comparison, the three-antenna system for GPR was fabricated and experimented in comparison with the conventional GPR configuration. The experimental results revealed that the three-antenna configuration was able to mitigate the ground bounce and antenna coupling effects, while the conventional GPR was interfered by the effect of ground reflection and mutual coupling of the antennas. The three-antenna configuration is thus suitable to be the front-end before extracting the natural poles. In addition, the frequency domain method is compatible with the three-antenna system in the determination of the natural poles for identification. As such, the proposed system for investigating the response in the frequency domain is operationally appropriate in GPR system.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Simple and Efficient SBR Implementation for RCS Calculation Using Target
           Scaling

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      Authors: Okyanus Tulgar;Kadir Durgut;A. Arif Ergin;
      Pages: 3680 - 3687
      Abstract: In order to alleviate the computational burden of the shooting and bouncing rays (SBRs) method in the radar cross section (RCS) analysis, an algorithm using target scaling is introduced in this article. This algorithm aims to reduce the number of rays that must be traced with time-consuming ray–triangle intersection tests. In order to achieve this, the target’s electrical length is reduced to a predefined value in each aspect angle. Then, only rays that hit the scaled target is traced without changing the analysis frequency. The RCS values for full-scaled model are estimated by using the ray displacements and field strengths calculated for the scaled model. This algorithm yields a significant decrease in the computational burden with a trade-off between analysis accuracy and time consumption. Analysis results show that the introduced algorithm and original SBR give very similar RCS results except at very low RCS points as depicted in the RCS versus aspect angle graphs. In addition, using a fixed frequency makes the algorithm applicable to not only perfectly electrical conducting (PEC) targets, but also targets coated with radar absorbing materials (RAMs).
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Adaptive Distributed Transceiver Synchronization Over a 90 m Microwave
           Wireless Link

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      Authors: Serge R. Mghabghab;Anton Schlegel;Jeffrey A. Nanzer;
      Pages: 3688 - 3699
      Abstract: We present an adaptive approach for synchronizing both the phase and frequency of radio frequency transceivers over 90 m wireless links to support distributed antenna array applications. To enable phase-coherent distributed operation between separate wireless nodes, the oscillators in the transceivers must operate at the same frequency, and their phases must be appropriately aligned to support beamsteering. Based on a spectrally sparse waveform, a self-mixing frequency demodulation circuit, and an adaptive control loop, we present a system capable of synchronizing the RF oscillators in separate transceivers over distances of 90 m. The approach is based on a multitone waveform designed for joint internode ranging and frequency transfer. A frequency reference is modulated onto one signal of a two-tone waveform transmitted by the primary node and is then demodulated and used to lock the oscillator of the secondary node. The secondary node retransmits the two-tone signal, which the primary node uses for a high-accuracy range measurement. From this range, the phase of the two transceivers can be aligned to support beamforming. We furthermore implemented an adaptive phase control approach to support high-accuracy phase coordination in changing environmental conditions. We demonstrate continuous high-accuracy links over a 90 m distance in an outdoor environment for durations up to seven days, demonstrating sufficient phase coordination in changing weather conditions to support distributed beamforming at frequencies up to 3 GHz.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • mm-Wave Chipless RFID Decoding: Introducing Image-Based Deep Learning
           Techniques

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      Authors: Larry M. Arjomandi;Grishma Khadka;Nemai C. Karmakar;
      Pages: 3700 - 3709
      Abstract: Chipless RFID tag decoding has some inherent degrees of uncertainty because there is no handshake protocol between chipless tags and readers. This article initially compares the outcome of different pattern recognition methods to decode some frequency-based tags in the mm-wave spectrum. It will be shown that these pattern recognition methods suffer from almost 2%–5% false decoding rate. To overcome this misdecoding problem, two novel methods of making images of the chipless tags are presented. The first method is making 2-D images based on side-looking aperture radar concepts, and the second one is making virtual 2-D images from the 1-D backscattering signals. Then, a 2-D decoding algorithm is suggested based on a convolutional neural network to decode those tag images and compare the results. It is shown that this combined decoding method has very high accuracy, and it almost eliminates any ambiguity and false decoding problems. This is the first time a deep learning method is used with image construction methods to decode chipless RFID tags.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Magneto-Mechanical Transmitters for Ultralow Frequency Near-Field Data
           Transfer

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      Authors: Rhinithaa P. Thanalakshme;Ali Kanj;JunHwan Kim;Elias Wilken-Resman;Jiheng Jing;Inbar H. Grinberg;Jennifer T. Bernhard;Sameh Tawfick;Gaurav Bahl;
      Pages: 3710 - 3722
      Abstract: Electromagnetic signals in the ultralow frequency (ULF) range below 3 kHz are well suited for underwater and underground wireless communication thanks to low signal attenuation and high penetration depth. However, it is challenging to design ULF transmitters that are simultaneously compact and energy efficient using traditional approaches, e.g., using coils or dipole antennas. Recent works have considered magneto-mechanical alternatives, in which ULF magnetic fields are generated using the motion of permanent magnets, since they enable extremely compact ULF transmitters that can operate with low energy consumption and are suitable for human-portable applications. Here we explore the design and operating principles of resonant magneto-mechanical transmitters (MMT) that operate over frequencies spanning a few 10 s of Hz up to 1 kHz. We experimentally demonstrate two types of MMT designs using both single-rotor and multirotor architectures. We study the nonlinear electro-mechanical dynamics of MMTs using point dipole approximation and magneto-static simulations. We further experimentally explore techniques to control the operation frequency and demonstrate amplitude modulation up to 10 bits-per-second. We additionally demonstrate how using oppositely polarized MMT modules can permit systems that have low dc-field but do not sacrifice the ac magnetic field produced.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Vector Modulation Approach for Secure Communications Based on 4-D
           Antenna Arrays

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      Authors: Chuanhong Qu;Kejin Chen;Weijun Long;Yikai Chen;Shi-Wei Qu;Jun Hu;Shiwen Yang;
      Pages: 3723 - 3732
      Abstract: A vector modulation approach based on 4-D antenna arrays is proposed for the directional modulation (DM) of physical-layer secure communication. This approach utilizes the time modulation function of 4-D arrays to generate identifiable vector information in desired directions while the vector information is distorted in undesired directions, thus increasing the transmission security as compared to previously reported DM schemes. The mutual coupling of antenna elements is taken into consideration for the accurate analysis of various scenarios. Moreover, in order to achieve multiuser secure communication and improve their security capability simultaneously, the dual-channel DM and dynamic DM are separately proposed and only high-speed radio frequency (RF) modulation switches are needed. Numerical and experimental results are presented for the demonstration of the capability and superiority of the proposed physical-layer secure communication based on 4-D arrays.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Generalized Formulation of Response Features for Reliable Optimization of
           Antenna Input Characteristics

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      Authors: Anna Pietrenko-Dabrowska;Slawomir Koziel;
      Pages: 3733 - 3748
      Abstract: Electromagnetic (EM)-driven parameter adjustment has become imperative in the design of modern antennas. It is necessary because the initial designs rendered through topology evolution, parameter sweeping, or theoretical models are often of poor quality and need to be improved to satisfy stringent performance requirements. Given multiple objectives, constraints, and a typically large number of geometry parameters, the design closure should be carried out through numerical optimization. Unfortunately, standard algorithms entail high CPU expenses and are prone to failure. Feature-based optimization (FBO) is one of the methods developed to alleviate these difficulties by reformulating the design task in terms of the characteristic points extracted from EM-simulated responses. FBO capitalizes on a less nonlinear relationship between the feature point coordinates and antenna dimensions as compared to the original responses (e.g., frequency characteristics). This leads to flattening the functional landscape to be handled, faster convergence of the optimization algorithms, and a possibility of mitigating the issues pertinent to multimodality. Notwithstanding, the response features have to be individually defined for each type of antenna response and tailored to a particular type of design specifications. This requires user experience and hinders the widespread application of FBO. This article proposes a generalized and unified feature point definition, which is suitable for the majority of typical antenna input characteristics (narrowband, multiband, enhanced bandwidth, and wideband) and performance specifications (matching improvement, bandwidth enhancement, and a mixture thereof). Our framework allows for an automated definition of the feature points given the performance specifications, along with their extraction from EM-simulated responses. The operation of the framework is illustrated using a range of planar antennas and favorably compared to conventional (nonfeatur--based) design closure task formulation.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Reconfigurable Dual-Band Capsule-Conformal Antenna Array for In-Body
           Bioelectronics

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      Authors: Denys Nikolayev;Anja K. Skrivervik;John S. Ho;Maxim Zhadobov;Ronan Sauleau;
      Pages: 3749 - 3761
      Abstract: Wireless in-body bioelectronics offer powerful biosensing and therapeutic capabilities. Efficient and robust in-body antenna designs are required to ensure a reliable through-body link, increase data rates, and reduce power budgets. This study proposes and demonstrates a pattern- and frequency-reconfigurable capsule-conformal antenna array that responds to the challenges of next-generation in-body bioelectronics. The array comprises two mirrored dual-band elements operating at 434 MHz and 2.45 GHz ISM bands. Tissue-matched dielectric loading of the array improves the radiation efficiency and ensures quasi tissue-independent operation for both bands. Due to the full ground plane, the antenna is shielded from the capsule payload. The achieved efficiencies are compared to the fundamental limitations and closely approach them. The realized gains are −28.9 and −18.6 dBi at 434 MHz and 2.45 GHz, respectively, when the array is placed in the center of a ø100-mm diameter spherical phantom with muscle-equivalent properties. Using a single switch, the array can be reconfigured to adjust the angular position of the nulls in the radiation pattern in both bands thereby enabling synthesis of an effectively null-free omnidirectional pattern. The array prototypes are fabricated, and the impedance and far-field radiation patterns are characterized to validate the design in tissue-equivalent liquid phantoms.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Optimal Sampling in Spherical Near-Field Antenna Measurements by Utilizing
           the Information Content of Spherical Wave Harmonics

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      Authors: Hamid Reza Behjoo;Abbas Pirhadi;Reza Asvadi;
      Pages: 3762 - 3771
      Abstract: In this article, we propose an efficient method that specifies the minimum number of samples and their locations to measure the spherical near-field (SNF) of antennas utilizing information-theoretic tools. To this end, spherical harmonics are investigated from the information-theoretic point of view. Our study determines the minimum required samples and provides a validation tool to assess the ability of a sampling scheme to recover the antenna characteristics by the measured data. Furthermore, an optimum sampling scheme is proposed by clustering the energy of vector spherical harmonics using the frame theory without any time-consuming iterative, which leads to a highly efficient SNF measurement procedure. The number of samples determined by the proposed method is only 50% of the Nyquist method, which provides significant advantages for storage and processing time. Our method additionally shows a great promise for the recovery of the far-field radiation pattern from near-field samples with the same performance as the Nyquist sampling on a sphere. To derive the proposed sampling scheme with the minimum redundancy, no prior information on the antenna is assumed. Finally, the proposed sampling scheme is validated on measurement data.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Contrast-Enhanced Microwave Cancer Detection Using Angle-of-Arrival
           Approach

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      Authors: Zheng Gong;Yifan Chen;Xiaoyou Lin;Michael J. Cree;
      Pages: 3772 - 3780
      Abstract: This article proposes a novel contrast-enhanced microwave cancer detection (MCD) system to accurately detect the location of a tumor targeted by nanoscale contrast agents. This system adopts the angle-of-arrival (AoA) positioning approach that is conventionally applied to the region where plane waves dominate the propagation. Hence, to ensure the effectiveness of the AoA approach when it is working in close proximity to the human body, a new algorithm is proposed to transfer the antenna’s radiation pattern from the far-field to the detection region where spherical waves can still be observed. This AoA-based MCD system requires fewer antennas than other radar-based positioning approaches, thereby creating a low-profile hardware architecture. In addition, during the detection process, a differential technique is incorporated in order to track the signal change due to the administration of contrast agents, which can significantly suppress the noise inside the biological medium. The AoA-based differential MCD system is numerically studied on an anatomically realistic breast phantom subject to a variety of signal-to-noise ratios (SNRs). The results show that the proposed system can successfully locate the tumor with an average resolution of 0.6 mm. When the SNR in the biological medium is 10 dB, the average positioning error is less than 1.5 mm with sensitivity maintained above 60%, which surpasses the performance of other similar systems. The system is also experimentally validated with a physical breast phantom and stepper-motor-driven rotating antennas, where the reconstructed image shows a minor deviation of 3.61 mm with that of the simulated one.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Design of Miniaturized Incident Angle-Insensitive 2.45 GHz RF-Based Energy
           Harvesting System for IoT Applications

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      Authors: Jeong-Su Park;Yu-Seong Choi;Wang-Sang Lee;
      Pages: 3781 - 3788
      Abstract: Using a license-free industrial, scientific, and medical (ISM) frequency band as 2.45 GHz, a miniaturized incident angle-insensitive radio frequency (RF) energy harvester design for the Internet-of-Things (IoT) applications is proposed. For incident angle insensitivity of ambient RF energy and a low-profile compact design, the proposed harvester is used to a two-layer printed circuit board (PCB) substrate, which consists of orthogonally deployed antennas with an $LC$ balun, impedance matching, and Dickson charge pump circuits at each layer. The dual-polarized antenna for miniaturized design uses a bowtie-shaped meander dipole antenna having orthogonal arrangement. By measuring the efficiency of each diode stage of the rectifier circuit, a two-stage Dickson charge pump circuit with optimal efficiency was selected, and the dc outputs of the two rectifier circuits are connected in parallel. This rectifier circuit has a conversion efficiency of up to 71.4% and harvests approximately 1.6 times more power than a single-polarized circuit from any incident ambient RF signal. Due to its compact size and improved harvesting power at various incident angles, the proposed energy harvester can act as a power source, such as many kinds of ultralow power consumption systems, such as IoT sensors and medical applications.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Active Millimeter Wave Imaging Using Leaky-Wave Focusing Antenna

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      Authors: Kevin Kipruto Mutai;Hiroyasu Sato;Qiang Chen;
      Pages: 3789 - 3798
      Abstract: In this article, an active millimeter-wave imaging system using two rectangular waveguide leaky-wave focusing antennas deployed in a quasi-monostatic transmitter and receiver pair is proposed. The broadband design method of the focusing antenna is presented, where the phase constant is derived from the radiation direction of a rectangular waveguide leaky-wave antenna. To eliminate the effect of mutual coupling between the transmitting and receiving antennas and scattering from the surrounding environment, the scattered field from the object is obtained by subtracting the incident field from the total field. The 1-D detection of conducting sphere, conducting and dielectric cylinders, and a conducting plate is performed by experiment to validate the imaging capability of the proposed system. The 2-D imaging of a conducting cylinder in free space and positioned in front of a human body phantom representing the human body is finally performed to simulate the practical application of the system.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Measurement of the Amplitude and Polarization of the Electric Field by
           Electromagnetic Infrared Thermography

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      Authors: Daniel Prost;
      Pages: 3799 - 3805
      Abstract: The ElectroMagnetic InfraRed (EMIR) method developed and used at ONERA provides a map of the amplitude of the electric field radiated by an antenna: a thin film of low conductivity is placed in front of the EM source, the electric field induces currents which heat the film by Joule effect; this heating is measured by an infrared camera. A low-frequency modulation of the signal associated with synchronous demodulation of the images allows eliminating the parasitic thermal phenomena. By using anisotropic films with conductivity patterns, we propose here for the first time a vector measurement of the electric field. In the case of linear polarization, this technique allows to obtain the field direction, and in the case of circular polarization, to measure the axial ratio. Furthermore, we show, with the help of a patterned array, that we can obtain the spatial structure of the near field, both in amplitude and direction.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Investigation of Axial Mode Dielectric Helical Antenna

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      Authors: Zhiwei Song;Hongxing Zheng;Yongjian Li;Erping Li;
      Pages: 3806 - 3811
      Abstract: An axial mode solid dielectric helical antenna (DHA) has been proposed, which is fabricated by using the 3-D printing technique. Fed manners of this antenna have been studied, including conformal coaxial probe and conformal metal strip line. The operating mode of dielectric helix has been analyzed in detail. Circular polarization is achieved by choosing appropriate sizes of the dielectric helix. Furthermore, a miniaturized axial mode DHA with deployable property is implemented. Measured results indicate that the proposed antenna has good radiation performance, such as circular polarization, high gain, and high radiation efficiency. Specially, the radiation patterns of the DHA have good symmetry in the 2 dB axial ratio range. The significant advantage of miniaturized DHA is light in weight, which is only 2.7% of the weight of a metal helical antenna with similar radiation characteristics. The antenna is a good candidate in wireless communication system.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Wideband Filtering Antenna Fed Through Hybrid Substrate Integrated
           Waveguide and Spoof Localized Surface Plasmon Structure

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      Authors: Zhenzhong Chen;Min Wang;Dongfang Guan;Zuping Qian;Wen Wu;Lei Zhu;
      Pages: 3812 - 3817
      Abstract: In this communication, we propose a novel feeding scheme to design a wideband filtering patch antenna. The antenna is composed of two substrates: the feeding and the radiating ones. Two circular patches are etched on the top surface of the radiating substrate as the radiators and a hybrid substrate integrated waveguide (SIW) and spoof localized surface plasmon (SLSP) structure is used as the feeding scheme. Due to abundant resonant modes and filtering feature of the hybrid SIW-SLSP structure, the antenna can radiate under the triple-mode resonance with high filtering performance. Moreover, the proposed filtering antenna has an independently adjustable capability of both low-band and high-band radiation nulls. The presented antenna is designed, fabricated, and measured. The measured results reveal that the operating bandwidth reaches up to 11.3%, ranging from 7.44 to 8.33 GHz. The peak gain of 10 dBi is obtained in passband with 10 dB gain suppression out of the band. This approach provides a simple way to design wideband filtering patch antenna, which can be easily integrated with planar circuit.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Dual-Band Circularly Polarized Shared-Aperture Antenna for 1U CubeSat
           Applications

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      Authors: Chunling Chen;
      Pages: 3818 - 3823
      Abstract: This communication presents a design of a dual-band circularly polarized antenna with structure reuse for one cubic unit (1U) CubeSat applications. It is a challenging to design an antenna with the limited space of a CubeSat platform. To improve the space utilization, an antenna is designed inspired by the concept of structure reuse. A meshed-like-structure is designed, which works as the radiator of a microstrip antenna at UHF band. However, it works as a partial reflective sheet for a Fabry–Perot resonator cavity antenna at C-band. Therefore, a microstrip patch antenna and a Fabry–Perot resonator cavity antenna share only single aperture. A shaped ground is used to decrease the resonance at the lower band. Then, the aperture of the antenna is only $0.3lambda _{0} ,times , 0.3lambda _{0}$ , which makes it easy to integrate with a 1U CubeSat. The measurement reveals that the antenna has a common bandwidth of ( $vert text{S}_{11}vert < -10$ dB, AR < 3 dB) 1% and 1.4%, an isolation higher than 35 and 20 dB, a peak gain of 5.82 and 13.75 dBic at UHF and C-band, respectively. The frequency ratio of these two bands reaches 6.4. The above properties make the proposed antenna suitable for a CubeSat system.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Circularly Polarized High Gain Coaxial Line Leaky Wave Antenna With
           Backfire Radiation

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      Authors: Yancy Nasirudeen;Mrinal Kanti Mandal;Ravi Shaw;
      Pages: 3824 - 3827
      Abstract: This communication presents a leaky wave antenna based on a standard rigid coaxial cable showing circular polarization (CP) in the backfire direction. Here, CP is achieved by using a sequential rotation scheme. Periodic slots are cut on the outer conductor of the cable leading to radiation from the $n = -1$ th fast space harmonic. The circular geometry of the coaxial cable allows to easily obtain space quadrature by rotating the successive slots by 90° about the cable axis. The required time quadrature for CP is obtained by slot-to-slot separation along the propagation direction. The antenna is designed and fabricated for X-band applications using a low-cost coaxial cable and is excited using a standard SMA connector. The measured gain is 20.26 dBic with 3 dB beamwidth of 14° at 10.26 GHz. The measured axial ratio of the left-handed CP antenna is below 1.8 dB in the backfire direction.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Pattern-Reconfigurable Filtering Patch Antenna Using Embedded Resonators
           and Switchable Elements

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      Authors: Jian An Liu;Yun Fei Cao;Xiu Yin Zhang;
      Pages: 3828 - 3833
      Abstract: In this communication, a pattern-reconfigurable filtering patch antenna is presented which consists of a driven patch, a stacked patch, an embedded filtering feeding line, and two vertical switchable elements with gaps from the suspended patches. Compared with the conventional stacked patch antenna, the proposed antenna does not increase the volume. A novel filtering feeding network is designed which consists of a hairpin-shaped resonator and a half-wavelength coupled microstrip line. It is used to generate the radiation nulls near the lower and higher passband edges. A U-shaped slot is etched on the driven patch to generate another radiation null. Three radiation nulls are excited to realize filtering performance. Meanwhile, the radiation beam of the proposed antenna can be reconfigured by switching the function of switchable elements between a director and a reflector using p-i-n diodes. Good radiation pattern reconfigurability, filtering, and wideband performance can be achieved simultaneously. The simulated and measured results show that the radiation beam can be switched to the directions of −33°, 33°, and 0°. The proposed antenna can maintain a wide operating bandwidth of 2.22–2.84 GHz (25%), out-of-band suppression of over 14 dB, and flat in-band gain of about 8 dBi in different states.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Broadband Polarization Conversion Metasurface for Antenna RCS Reduction

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      Authors: Jie Liu;Jian-Ying Li;Zhi Ning Chen;
      Pages: 3834 - 3839
      Abstract: A broadband polarization conversion metasurface (PCM) is proposed for reducing radar cross section (RCS) of antenna. The unit cell of the PCM consists of two pairs of tapered L-shaped strips, a layer of air, and a ground plane. The PCM unit achieves polarization rotation (PR) bandwidth of 117.2% with the polarization conversion ratio (PCR) of 90%. The broadband characteristics of the PCM are studied by an equivalent circuit. The chessboard PCM reduces RCS under a linear polarized (LP) incident wave. The PCM is integrated into a dual-polarized 2 $times $ 2 H-shaped slot array antenna for RCS reduction. The measured results show that the monostatic RCS of the antenna is reduced by about 10 dB in the frequency range of 9.6–33.1 GHz and 9.8–33.2 GHz for $x$ - and $y$ -polarization under normal incidence, respectively, while the radiation performance of the antenna remains unchanged.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Cavity-Backed Antenna Using SISL Technology for 77 GHz Band Application

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      Authors: Xihui Teng;Yu Luo;Ningning Yan;Kaixue Ma;
      Pages: 3840 - 3845
      Abstract: A cavity-backed antenna based on substrate-integrated suspended line (SISL) technology is proposed for 77 GHz applications. The antenna is designed to be self-packaged using six substrate layers with embedded air cavities. Two rows of metal holes surround the core circuit to form the cavity and reduce the leaked field loss. Patches are printed in G5 and G6 layer and connected by metalized holes to form the double-side SISL with part of the substrate excavation to reduce the substrate loss. Thus, the simulation efficiency of better than 93% is achieved. Because of the cavity structure, the standing wave resonant mode can be obtained and achieve broadside radiation. A predominantly TE710 aperture field is obtained by adjusting the sizes of the backing cavity. The measured result shows that the proposed antenna has a −10 dB bandwidth from 75.6 to 81 GHz, covering 77 GHz automotive radar band and the max gain is 14.4 dBi. Based on this antenna, we design a differential-fed antenna array with a max gain of 17.5 dBi at 79 GHz.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • 5G SAR-Reduction MIMO Antenna With High Isolation for Full Metal-Rimmed
           Tablet Device

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      Authors: Yixiang Fang;Ying Liu;Yongtao Jia;Yunxue Xu;Ben Lai;
      Pages: 3846 - 3851
      Abstract: This communication focuses on the specific absorption rate (SAR) reduction of multiple-input–multiple-output (MIMO) antenna with high isolation for fifth-generation (5G) full metal-rimmed tablet devices. This is the first study to undertake a longitudinal analysis between equalization mode and reduction of SAR. Therefore, the study makes a major contribution to the research on the reduction of SAR by demonstrating the cancellation of inverted phase currents generated by the equalization mode. In addition, the utilization of equalization mode and full metal-rim avoids a 44% decrease in efficiency caused by hand grip. Furthermore, the isolation capacitance is utilized to suppress the traveling wave on the ground plane. As a result, the isolation of the MIMO antenna is improved by 12.94 dB. An $8times 8$ MIMO tablet array antenna is manufactured to validate the simulation. The measured maximum normalized values of 0 mm body SAR averaged over any 1 g tissue is 0.4 W/kg, which is far below the standard of Institute of Electrical and Electronics Engineers (IEEE) and U.S. Federal Communications Commission (FCC). The measured −6 dB impedance bandwidth is 3.4–3.6 GHz and isolation is better than 20.11 dB. The measured efficiency is higher than 53% and envelop correlation coefficient (ECC) is less than 0.17.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Low-Profile Dual-Band Dual-Circularly Polarized Folded Transmitarray
           Antenna With Independent Beam Control

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      Authors: Haoyu Lei;Ying Liu;Yongtao Jia;Zhenzhen Yue;Xing Wang;
      Pages: 3852 - 3857
      Abstract: This communication presents a low-profile, compact, high gain dual-band and dual-circularly polarized (CP) folded transmitarray antenna (FTA) with independent beam control at Ku-band. The element with independent phase control capability in two bands is designed to achieve the functionality of linear polarization to different circular polarization conversion. To reduce the profile of the whole FTA, a dual-band and dual-linearly polarized patch antenna is adopted as the feed source. By controlling the phase distribution and circular polarization of the transmitarray (TA) according to the phase compensation principle, the proposed antenna can radiate left-hand CP (LCP) waves and right-hand CP (RCP) waves at 12 and 15 GHz, respectively. On the basis, three typical FTA prototypes with different beam directions are simulated to validate the capability of independent beam control. Two of the prototypes are fabricated and measured, and the results are shown in reasonable agreement with the simulation. The proposed antenna not only reduces the profile by 2/3 compared to the traditional TA antenna, but also has the advantages of compact planar structure, low cost, high gain, and easy integration, which presents great application potential in two-way satellite communication systems with limited volume and space.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Design of Zero Clearance SIW Endfire Antenna Array Using Machine
           Learning-Assisted Optimization

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      Authors: Jin Zhang;Mobayode O. Akinsolu;Bo Liu;Shuai Zhang;
      Pages: 3858 - 3863
      Abstract: In this communication, a substrate integrated waveguide (SIW) end-fire antenna array with zero clearance is proposed for fifth-generation (5G) mobile applications using machine learning-assisted optimization. In particular, a novel impedance matching architecture that involves three arbitrary pad-loading metallic vias is investigated and adopted for the antenna element. Due to the stringent design requirements, the locations and sizes of the vias and pads are obtained via a state-of-the-art machine learning assisted antenna design exploration method, parallel surrogate model-assisted hybrid differential evolution for antenna synthesis (PSADEA). Keeping a very low profile, the array optimized by PSADEA covers an operating frequency bandwidth from 36 to 40 GHz. The in-band total efficiency is generally better than 60% and the peak gain is above 5 dBi. The beam scanning range at 39 GHz covers from −20° to 35°.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Planar, Polarization-Switchable Endfire and ±Broadside Millimeter-Wave
           Antenna Array Without Lumped Components

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      Authors: Ahmed Abdelmottaleb Omar;Jaehyun Choi;Jonghyun Kim;Junho Park;Beakjun Seong;Jongwoo Lee;Wonbin Hong;
      Pages: 3864 - 3869
      Abstract: A planar antenna array exhibiting polarization-switchable endfire and ±broadside radiation without the employment of lumped components is proposed. The antenna is denoted as symmetrically stacked planar antenna (SSPA), which utilizes the phase difference between the top and bottom patches to enable dual-linear/circular polarized hemispheric radiation. This communication focuses on the dual-linear polarized aspect. One polarization is achieved when a 180° phase difference exists between the first-set of ports, while the perpendicular polarization is accomplished when the second-set of ports are in-phase. A four-element array is constructed to exemplify this concept at 28 GHz, and the main beam is steered across the sphere. A comparison with other designs reported in the literature is conducted to highlight the salient points of the proposed methodology regarding planar, dual-polarized, and lumped-components-free features. To validate the predicted and simulated results, a prototype of the four-element array is fabricated and measured. The measured results show that the proposed array can steer the beam from 0° to 55° in all directions for both linear polarizations.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Differential-Fed Pattern-Reconfigurable Dielectric Patch Antenna and Array
           With Low Cross-Polarization

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      Authors: Xue-Ying Wang;Shi-Chang Tang;Jian-Xin Chen;
      Pages: 3870 - 3875
      Abstract: A novel differential-fed dielectric patch (DP) antenna with beam steering capability is investigated in this communication. The TEmn mode in the DP resonator is theoretically analyzed to provide guidance for the subsequent antenna design. The high-order TE12 mode that can be differentially excited is selected as the operating mode to further enhance the gain. Based on this, three parallel coupling slots loaded with p-i-n diodes are used as a beam steering structure. By controlling the ON-/OFF-state of the p-i-n diodes to change the $E$ -field distribution of the TE12 mode, the main beam can be switched to five directions. The measured gain of each state is higher than 7 dBi, and the peak value reaches 8.1 dBi. The beam steering structure and differential-fed scheme show good coordination, which effectively suppresses the deterioration of cross-polarization caused by structural asymmetry. The cross-polarization of each state is lower than −26 dB. To further verify the scalability of the proposed ideal, a 1 $times $ 4 array fed by two dual Marchand baluns is implemented, which well maintains the beam steering capability and low cross-polarization. Reasonable agreement is obtained between the simulated and measured results. The proposed DP antenna provides a suitable candidate for indoor wireless communication.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • A Wideband Circularly Polarized Magneto-Electric Dipole Antenna Array for
           Millimeter-Wave Applications

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      Authors: Lei Xiang;Fan Wu;Chao Yu;Zhi Hao Jiang;Yu Yao;Wei Hong;
      Pages: 3876 - 3881
      Abstract: A wideband circularly polarized (CP) magneto-electric (ME) dipole antenna is presented in this communication. The uniqueness of this design stands from the fact that the electric dipoles are 3-D-meandered and shorted to the ground plane at the edges of patches, respectively. By this means, two orthogonal ME-dipole modes with similar magnitudes and phase quadrature are well excited. Thus, a wideband CP ME-dipole antenna is achieved. Simulation results indicate that the antenna element achieves a wide impedance bandwidth of 49.6% (24.7–41 GHz) and a 3 dB axial ratio (AR) bandwidth of 50.4% (26.7–44.7 GHz) with a peak gain of 8 dBic. For proof-of-concept demonstration, a 4 $times $ 4 CP ME-dipole antenna array is investigated, implemented, and measured. The measurement results of the antenna array show a wide impedance bandwidth of 50% (24.5–40.8 GHz) and a 3 dB AR bandwidth of 44% (27.5–43 GHz) with a maximum gain of 19.2 dBic. The proposed CP antenna array demonstrates distinctive properties, such as broad impedance and AR bandwidth, stable gain, symmetrical radiation patterns, and ease of integration.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Wideband Circularly Polarized Septum Antenna Array With Ridge Gap
           Waveguide Feeding Network for Wireless Application

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      Authors: Kailai Wu;Yuan Yao;Xiaohe Cheng;Tao Xiu;Junsheng Yu;Xiaodong Chen;
      Pages: 3882 - 3887
      Abstract: A full corporate feeding $8times $ 8 circularly polarized (CP) planar antenna array using septum antenna elements for millimeter-wave (mmWave) frequency band applications is reported. Widebands for both the impedance and axial ratio (AR) bandwidths and high efficiency are guaranteed by the antenna array attributed to septum elements and feeding network based on the metal ridge gap waveguide (RGW). For the analyzing $2times $ 2 sub-array containing a feeding structure, simulated results show that the impedance bandwidth ( $vert S_{11}vert < -10$ dB) of 31.4%, AR bandwidth (AR < 3 dB) of 32.6%, and maximum gain of 29.2 dBic are realized. For the practical fabricated 8 $times $ 8 antenna array prototype, measured results reveal that its impedance bandwidth ( $vert S_{11}vert < -10$ dB) is 31.5%, overlap AR bandwidth (AR < 3 dB) is 33.1%, and maximum measured gain value is 28.4 dBic with a maximum aperture efficiency of 85%. With such performances, the proposed CP antenna array would be a promising candidate for mmWave communication systems.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Synthesis Approach of Quasi-Isotropic Dipole Arrays Based on the Vector
           Effective Height Formulation

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      Authors: Constant M. A. Niamien;
      Pages: 3888 - 3893
      Abstract: This communication presents a synthesis approach of collocated, orthogonal quasi-isotropic antenna arrays of electric dipoles based on the vector effective height formulation. The proposed formulation derives the optimum tripole (3-D) as the best quasi-isotropic antenna, exhibiting “just” a null pair compared with the entire horizontal plane for the well-known turnstile antenna. Full-wave simulations and experiments confirm the theoretical results derived in both $theta $ - and $phi $ -polarizations.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Meta-Surface Cavity-Based Waveguide Slot Array for Dual-Circularly
           Polarized Dual Beam

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      Authors: Yao Kan;Rui Yang;Aofang Zhang;Zhenya Lei;Yongchang Jiao;Jianfeng Li;
      Pages: 3894 - 3898
      Abstract: We introduce a meta-surface cavity into the waveguide slot array design and demonstrate the perfect generation of dual-circularly polarized (CP) dual-beams, where the cavity consists of meta-surface coated dielectric substrate surrounded by metallic vias and metal walls. When integrated with the rectangular waveguide, the meta-surface cavity functions as the leaky wave passage, capable of coupling the linearly polarized incidence from the feed into the cavity and releasing the resonant mode with birefringent radiations of right-hand and left-hand CP waves. Our design, performing the beam splitting and polarization conversion simultaneously as a waveguide slot array, should pave the way for building up more advanced meta-surface-based architectures for the manipulations of electromagnetic fields in the transmission regime.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • High-Efficiency Excitation of Spoof Surface Plasmon Polaritons Through
           Rectangular Waveguide Using Dipole Antenna

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      Authors: Huali Zhu;Yong Zhang;Longfang Ye;Zhang Dang;Ruimin Xu;Bo Yan;
      Pages: 3899 - 3903
      Abstract: In this communication, a high-efficiency rectangular waveguide-to-spoof surface plasmon polaritons transmission line (SSPPs TL) transition operating within terahertz frequencies is demonstrated. Terahertz signal fed by the rectangular waveguide is first coupled to the planar circuit through the dipole antenna. And then a taper and double-sided SSPPs TL are used to transform the resonant mode in the dipole antenna to the SSPPs mode and achieve impedance and momentum matching. The high transmission performance of the SSPPs TL is obtained by etching a series of periodically corrugated grooves on the metal strip in the top layer and a ground pad connected to the convexity of the rectangular waveguide is employed in the bottom layer. A back-to-back transition prototype was fabricated on a $50~mu text{m}$ -thickness quartz substrate and designed for a terahertz device with WR-4.3 standard rectangular waveguide. The measured results show that the insertion loss is lower than 2 dB from 195 to 250 GHz, and the in-band return loss is better than 10 dB. To the best of our knowledge, this work presents the rectangular waveguide-to-SSPPs TL transition using a dipole antenna for the first time, which has potential applications for plasmonic-integrated circuits and systems in the terahertz range.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Maximum Achievable Gain of Annular-Shaped Beams

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      Authors: Arun Bhattacharyya;Joshua Gustafson;Thomas Hand;Joseph Torres;
      Pages: 3904 - 3909
      Abstract: The maximum achievable gain and the corresponding source distribution for an annular or “donut”-shaped beam produced by a circular aperture are studied. Expressing the source in terms of orthogonal basis functions and then applying Lagrange’s multiplier method, the optimum source distribution is determined. The residue calculus is then invoked for the closed-form expressions. Numerical results are shown and discussed. In applications such as direction finding and satellite tracking systems on moving vehicles, a high-gain annular beam is suitable for maintaining uninterrupted connectivity.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Loop-Star Functions Including Multibranch Rao-Wilton-Glisson Basis
           Functions

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      Authors: Shifeng Huang;Gaobiao Xiao;Yuyang Hu;Rui Liu;Junfa Mao;
      Pages: 3910 - 3915
      Abstract: A quasi-Helmholtz decomposition with loop-star basis functions including multibranch Rao-Wilton-Glisson (MB-RWG) basis functions is proposed for electromagnetic scattering problems on an object with multiple surfaces. The loop and star basis functions in the interior region of each surface are generated with RWG functions, and those loop functions and star functions at the bordering lines between different surfaces are constructed with MB-RWG and RWG functions. With MB-RWG functions, the proposed loop-star scheme can be applied to two adjacent surfaces with different mesh resolutions directly. Some numerical examples are presented at low frequencies to verify the accuracy of the method.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Advanced Parallelism of DGTD Method With Local Time Stepping Based on
           Novel MPI + MPI Unified Parallel Algorithm

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      Authors: Zhen Guo Ban;Yan Shi;Peng Wang;
      Pages: 3916 - 3921
      Abstract: In this communication, a novel message passing interface (MPI) parallel algorithm for nodal discontinuous Galerkin time-domain (NDGTD) method has been developed. A unified MPI + MPI technique has been introduced for extreme parallelism on a large-scale computer cluster. Through the data transmission between CPU nodes using MPI persistent nonblocking two-side communication and the direct data connection between processors in the same node via MPI shared memory windows, a two-layered parallel architecture is implemented to minimize the communication. To further accelerate the solution of the multiscale problems, the local time stepping (LTS) technique has been employed in the NDGTD method. A fast time step estimation method has been presented in this communication. With high overlap between the information transmission and the data calculation, the proposed MPI + MPI scheme overcomes the degradation of the parallel efficiency of the pure MPI technique in the scenario of the LTS technique and the large-scale CPU cores. Up to 94% parallel efficiency in 6400 CPU cores is achieved for the average single-core loading about 1700 finite elements, and 18 times acceleration for time step estimation can be obtained with the fourth-order basis function. Three practical complex examples are given to demonstrate a good performance of the proposed method.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Comments on “Development of Cross-Polar Orientation-Insensitive
           Chipless RFID Tags”

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      Authors: O. Rance;N. Barbot;E. Perret;
      Pages: 3922 - 3923
      Abstract: Babaeian and Karmakar present a technique for designing resonant scatterers that display a cross-polarization reflection that remains consistent (i.e., non-zero) regardless of the orientation of the target. The authors claim that this property can be obtained simply by duplicating, rotating, and arranging the position of a unit cell. We will show in this comment that all the design techniques presented by Babaeian and Karmakar in Section III lead to multiple cancellations of the cross-polarization component of the backscattered $E$ -field. Therefore, the measurement results presented by Babaeian and Karmakar cannot be justified by the theory presented in Section III of the same article.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Corrections to “Spherical Mode-Based Analysis of Wireless Power Transfer
           Between Two Antennas” [Jun 14 3054-3063]

    • Free pre-print version: Loading...

      Authors: Yoon Goo Kim;Sangwook Nam;
      Pages: 3924 - 3925
      Abstract: In the above article [1], some equations, sentences, and figures were changed. Furthermore, some sentences were added.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • Frontiers in Computational Electromagnetics

    • Free pre-print version: Loading...

      Pages: 3926 - 3926
      Abstract: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • IEEE Open Access

    • Free pre-print version: Loading...

      Pages: 3927 - 3927
      Abstract: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
  • TechRxiv: Share Your Preprint Research with the World!

    • Free pre-print version: Loading...

      Pages: 3928 - 3928
      Abstract: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.
      PubDate: May 2022
      Issue No: Vol. 70, No. 5 (2022)
       
 
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