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  Subjects -> ELECTRONICS (Total: 201 journals)
Showing 1 - 200 of 277 Journals sorted alphabetically
Acta Electronica Malaysia     Open Access  
Advanced Materials Technologies     Hybrid Journal  
Advances in Electrical and Electronic Engineering     Open Access   (Followers: 9)
Advances in Electronics     Open Access   (Followers: 99)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Power Electronics     Open Access   (Followers: 39)
Advancing Microelectronics     Hybrid Journal  
American Journal of Electrical and Electronic Engineering     Open Access   (Followers: 28)
Annals of Telecommunications     Hybrid Journal   (Followers: 9)
APSIPA Transactions on Signal and Information Processing     Open Access   (Followers: 9)
Archives of Electrical Engineering     Open Access   (Followers: 15)
Australian Journal of Electrical and Electronics Engineering     Hybrid Journal  
Batteries     Open Access   (Followers: 9)
Batteries & Supercaps     Hybrid Journal   (Followers: 4)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 31)
Bioelectronics in Medicine     Hybrid Journal  
Biomedical Instrumentation & Technology     Hybrid Journal   (Followers: 6)
BULLETIN of National Technical University of Ukraine. Series RADIOTECHNIQUE. RADIOAPPARATUS BUILDING     Open Access   (Followers: 2)
Bulletin of the Polish Academy of Sciences : Technical Sciences     Open Access   (Followers: 1)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 47)
China Communications     Full-text available via subscription   (Followers: 9)
Chinese Journal of Electronics     Hybrid Journal  
Circuits and Systems     Open Access   (Followers: 15)
Consumer Electronics Times     Open Access   (Followers: 5)
Control Systems     Hybrid Journal   (Followers: 302)
ECTI Transactions on Computer and Information Technology (ECTI-CIT)     Open Access  
ECTI Transactions on Electrical Engineering, Electronics, and Communications     Open Access   (Followers: 2)
Edu Elektrika Journal     Open Access   (Followers: 1)
Electrica     Open Access  
Electronic Design     Partially Free   (Followers: 123)
Electronic Markets     Hybrid Journal   (Followers: 7)
Electronic Materials Letters     Hybrid Journal   (Followers: 4)
Electronics     Open Access   (Followers: 108)
Electronics and Communications in Japan     Hybrid Journal   (Followers: 10)
Electronics For You     Partially Free   (Followers: 103)
Electronics Letters     Hybrid Journal   (Followers: 26)
Elkha : Jurnal Teknik Elektro     Open Access  
Energy Harvesting and Systems     Hybrid Journal   (Followers: 4)
Energy Storage     Hybrid Journal   (Followers: 1)
Energy Storage Materials     Full-text available via subscription   (Followers: 4)
EPE Journal : European Power Electronics and Drives     Hybrid Journal  
EPJ Quantum Technology     Open Access   (Followers: 1)
EURASIP Journal on Embedded Systems     Open Access   (Followers: 11)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Foundations and Trends® in Communications and Information Theory     Full-text available via subscription   (Followers: 6)
Foundations and Trends® in Signal Processing     Full-text available via subscription   (Followers: 10)
Frequenz     Hybrid Journal   (Followers: 1)
Frontiers of Optoelectronics     Hybrid Journal   (Followers: 1)
IACR Transactions on Symmetric Cryptology     Open Access  
IEEE Antennas and Propagation Magazine     Hybrid Journal   (Followers: 100)
IEEE Antennas and Wireless Propagation Letters     Hybrid Journal   (Followers: 81)
IEEE Embedded Systems Letters     Hybrid Journal   (Followers: 56)
IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology     Hybrid Journal   (Followers: 1)
IEEE Journal of Emerging and Selected Topics in Power Electronics     Hybrid Journal   (Followers: 52)
IEEE Journal of the Electron Devices Society     Open Access   (Followers: 9)
IEEE Journal on Exploratory Solid-State Computational Devices and Circuits     Hybrid Journal   (Followers: 1)
IEEE Letters on Electromagnetic Compatibility Practice and Applications     Hybrid Journal   (Followers: 2)
IEEE Magnetics Letters     Hybrid Journal   (Followers: 7)
IEEE Nanotechnology Magazine     Hybrid Journal   (Followers: 42)
IEEE Open Journal of Circuits and Systems     Open Access   (Followers: 1)
IEEE Open Journal of Industry Applications     Open Access   (Followers: 1)
IEEE Open Journal of the Industrial Electronics Society     Open Access   (Followers: 1)
IEEE Power Electronics Magazine     Full-text available via subscription   (Followers: 77)
IEEE Pulse     Hybrid Journal   (Followers: 5)
IEEE Reviews in Biomedical Engineering     Hybrid Journal   (Followers: 22)
IEEE Solid-State Circuits Letters     Hybrid Journal   (Followers: 1)
IEEE Solid-State Circuits Magazine     Hybrid Journal   (Followers: 13)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 361)
IEEE Transactions on Antennas and Propagation     Full-text available via subscription   (Followers: 74)
IEEE Transactions on Automatic Control     Hybrid Journal   (Followers: 59)
IEEE Transactions on Autonomous Mental Development     Hybrid Journal   (Followers: 8)
IEEE Transactions on Biomedical Engineering     Hybrid Journal   (Followers: 38)
IEEE Transactions on Broadcasting     Hybrid Journal   (Followers: 13)
IEEE Transactions on Circuits and Systems for Video Technology     Hybrid Journal   (Followers: 26)
IEEE Transactions on Consumer Electronics     Hybrid Journal   (Followers: 45)
IEEE Transactions on Electron Devices     Hybrid Journal   (Followers: 19)
IEEE Transactions on Geoscience and Remote Sensing     Hybrid Journal   (Followers: 219)
IEEE Transactions on Haptics     Hybrid Journal   (Followers: 4)
IEEE Transactions on Industrial Electronics     Hybrid Journal   (Followers: 76)
IEEE Transactions on Industry Applications     Hybrid Journal   (Followers: 40)
IEEE Transactions on Information Theory     Hybrid Journal   (Followers: 26)
IEEE Transactions on Learning Technologies     Full-text available via subscription   (Followers: 12)
IEEE Transactions on Power Electronics     Hybrid Journal   (Followers: 79)
IEEE Transactions on Services Computing     Hybrid Journal   (Followers: 4)
IEEE Transactions on Signal and Information Processing over Networks     Hybrid Journal   (Followers: 14)
IEEE Transactions on Software Engineering     Hybrid Journal   (Followers: 79)
IEEE Women in Engineering Magazine     Hybrid Journal   (Followers: 11)
IEEE/OSA Journal of Optical Communications and Networking     Hybrid Journal   (Followers: 16)
IEICE - Transactions on Electronics     Full-text available via subscription   (Followers: 12)
IEICE - Transactions on Information and Systems     Full-text available via subscription   (Followers: 5)
IET Cyber-Physical Systems : Theory & Applications     Open Access   (Followers: 1)
IET Energy Systems Integration     Open Access   (Followers: 1)
IET Microwaves, Antennas & Propagation     Hybrid Journal   (Followers: 35)
IET Nanodielectrics     Open Access  
IET Power Electronics     Hybrid Journal   (Followers: 59)
IET Smart Grid     Open Access   (Followers: 1)
IET Wireless Sensor Systems     Hybrid Journal   (Followers: 18)
IETE Journal of Education     Open Access   (Followers: 4)
IETE Journal of Research     Open Access   (Followers: 11)
IETE Technical Review     Open Access   (Followers: 13)
IJEIS (Indonesian Journal of Electronics and Instrumentation Systems)     Open Access   (Followers: 3)
Industrial Technology Research Journal Phranakhon Rajabhat University     Open Access  
Informatik-Spektrum     Hybrid Journal   (Followers: 2)
Instabilities in Silicon Devices     Full-text available via subscription   (Followers: 1)
Intelligent Transportation Systems Magazine, IEEE     Full-text available via subscription   (Followers: 13)
International Journal of Advanced Research in Computer Science and Electronics Engineering     Open Access   (Followers: 18)
International Journal of Advances in Telecommunications, Electrotechnics, Signals and Systems     Open Access   (Followers: 12)
International Journal of Antennas and Propagation     Open Access   (Followers: 11)
International Journal of Applied Electronics in Physics & Robotics     Open Access   (Followers: 4)
International Journal of Computational Vision and Robotics     Hybrid Journal   (Followers: 5)
International Journal of Control     Hybrid Journal   (Followers: 11)
International Journal of Electronics     Hybrid Journal   (Followers: 7)
International Journal of Electronics and Telecommunications     Open Access   (Followers: 13)
International Journal of Granular Computing, Rough Sets and Intelligent Systems     Hybrid Journal   (Followers: 3)
International Journal of High Speed Electronics and Systems     Hybrid Journal  
International Journal of Hybrid Intelligence     Hybrid Journal  
International Journal of Image, Graphics and Signal Processing     Open Access   (Followers: 16)
International Journal of Microwave and Wireless Technologies     Hybrid Journal   (Followers: 10)
International Journal of Nanoscience     Hybrid Journal   (Followers: 1)
International Journal of Numerical Modelling: Electronic Networks, Devices and Fields     Hybrid Journal   (Followers: 4)
International Journal of Power Electronics     Hybrid Journal   (Followers: 25)
International Journal of Review in Electronics & Communication Engineering     Open Access   (Followers: 4)
International Journal of Sensors, Wireless Communications and Control     Hybrid Journal   (Followers: 10)
International Journal of Systems, Control and Communications     Hybrid Journal   (Followers: 4)
International Journal of Wireless and Microwave Technologies     Open Access   (Followers: 6)
International Transaction of Electrical and Computer Engineers System     Open Access   (Followers: 2)
JAREE (Journal on Advanced Research in Electrical Engineering)     Open Access  
Journal of Biosensors & Bioelectronics     Open Access   (Followers: 4)
Journal of Advanced Dielectrics     Open Access   (Followers: 1)
Journal of Artificial Intelligence     Open Access   (Followers: 12)
Journal of Circuits, Systems, and Computers     Hybrid Journal   (Followers: 4)
Journal of Computational Intelligence and Electronic Systems     Full-text available via subscription   (Followers: 1)
Journal of Electrical and Electronics Engineering Research     Open Access   (Followers: 37)
Journal of Electrical Bioimpedance     Open Access  
Journal of Electrical Bioimpedance     Open Access   (Followers: 2)
Journal of Electrical Engineering & Electronic Technology     Hybrid Journal   (Followers: 7)
Journal of Electrical, Electronics and Informatics     Open Access  
Journal of Electromagnetic Analysis and Applications     Open Access   (Followers: 8)
Journal of Electromagnetic Waves and Applications     Hybrid Journal   (Followers: 9)
Journal of Electronic Design Technology     Full-text available via subscription   (Followers: 6)
Journal of Electronic Science and Technology     Open Access   (Followers: 1)
Journal of Electronics (China)     Hybrid Journal   (Followers: 5)
Journal of Energy Storage     Full-text available via subscription   (Followers: 4)
Journal of Engineered Fibers and Fabrics     Open Access   (Followers: 2)
Journal of Field Robotics     Hybrid Journal   (Followers: 3)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 181)
Journal of Information and Telecommunication     Open Access   (Followers: 1)
Journal of Intelligent Procedures in Electrical Technology     Open Access   (Followers: 3)
Journal of Low Power Electronics     Full-text available via subscription   (Followers: 10)
Journal of Low Power Electronics and Applications     Open Access   (Followers: 10)
Journal of Microelectronics and Electronic Packaging     Hybrid Journal   (Followers: 1)
Journal of Microwave Power and Electromagnetic Energy     Hybrid Journal   (Followers: 3)
Journal of Microwaves, Optoelectronics and Electromagnetic Applications     Open Access   (Followers: 11)
Journal of Nuclear Cardiology     Hybrid Journal  
Journal of Optoelectronics Engineering     Open Access   (Followers: 4)
Journal of Physics B: Atomic, Molecular and Optical Physics     Hybrid Journal   (Followers: 30)
Journal of Power Electronics & Power Systems     Full-text available via subscription   (Followers: 11)
Journal of Semiconductors     Full-text available via subscription   (Followers: 5)
Journal of Sensors     Open Access   (Followers: 26)
Journal of Signal and Information Processing     Open Access   (Followers: 9)
Jurnal ELTIKOM : Jurnal Teknik Elektro, Teknologi Informasi dan Komputer     Open Access  
Jurnal Rekayasa Elektrika     Open Access  
Jurnal Teknik Elektro     Open Access  
Jurnal Teknologi Elektro     Open Access  
Kinetik : Game Technology, Information System, Computer Network, Computing, Electronics, and Control     Open Access  
Majalah Ilmiah Teknologi Elektro : Journal of Electrical Technology     Open Access   (Followers: 2)
Metrology and Measurement Systems     Open Access   (Followers: 6)
Microelectronics and Solid State Electronics     Open Access   (Followers: 28)
Nanotechnology, Science and Applications     Open Access   (Followers: 6)
Nature Electronics     Hybrid Journal   (Followers: 1)
Networks: an International Journal     Hybrid Journal   (Followers: 5)
Open Electrical & Electronic Engineering Journal     Open Access  
Open Journal of Antennas and Propagation     Open Access   (Followers: 9)
Paladyn. Journal of Behavioral Robotics     Open Access   (Followers: 1)
Power Electronics and Drives     Open Access   (Followers: 2)
Problemy Peredachi Informatsii     Full-text available via subscription  
Progress in Quantum Electronics     Full-text available via subscription   (Followers: 7)
Radiophysics and Quantum Electronics     Hybrid Journal   (Followers: 2)
Recent Advances in Communications and Networking Technology     Hybrid Journal   (Followers: 4)
Recent Advances in Electrical & Electronic Engineering     Hybrid Journal   (Followers: 11)
Research & Reviews : Journal of Embedded System & Applications     Full-text available via subscription   (Followers: 6)
Revue Méditerranéenne des Télécommunications     Open Access  
Security and Communication Networks     Hybrid Journal   (Followers: 2)
Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of     Hybrid Journal   (Followers: 56)
Semiconductors and Semimetals     Full-text available via subscription   (Followers: 1)
Sensing and Imaging : An International Journal     Hybrid Journal   (Followers: 2)
Solid State Electronics Letters     Open Access  
Solid-State Electronics     Hybrid Journal   (Followers: 9)
Superconductor Science and Technology     Hybrid Journal   (Followers: 3)
Synthesis Lectures on Power Electronics     Full-text available via subscription   (Followers: 3)
Technical Report Electronics and Computer Engineering     Open Access  
TELE     Open Access  
Telematique     Open Access  
TELKOMNIKA (Telecommunication, Computing, Electronics and Control)     Open Access   (Followers: 9)
Transactions on Electrical and Electronic Materials     Hybrid Journal   (Followers: 1)
Universal Journal of Electrical and Electronic Engineering     Open Access   (Followers: 7)
Ural Radio Engineering Journal     Open Access   (Followers: 1)
Visión Electrónica : algo más que un estado sólido     Open Access   (Followers: 1)
Wireless and Mobile Technologies     Open Access   (Followers: 6)
Wireless Power Transfer     Full-text available via subscription   (Followers: 4)

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Similar Journals
Journal Cover
IEEE Transactions on Antennas and Propagation
Journal Prestige (SJR): 1.309
Citation Impact (citeScore): 5
Number of Followers: 74  
  Full-text available via subscription Subscription journal
ISSN (Print) 0018-926X
Published by IEEE Homepage  [228 journals]
  • IEEE Transactions on Antennas and Propagation
    • 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: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • IEEE Transactions on Antennas and Propagation
    • 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: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Institutional Listings
    • Abstract: Presents the institutional listings for this issue of the publication.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • In Memoriam: Associate Editor Prof. M. Daneshmand
    • Pages: 631 - 632
      Abstract: It is with heartfelt sadness that we inform you of the tragic loss of our Associate Editor Prof. Mojgan Daneshmand, who was a passenger on the Ukraine International Airlines flight that crashed after takeoff from Teheran International Airport on January 8, 2020. Her husband, Prof. Pedram Mousavi, and their daughters, Darya and Darina, also died in the crash. Prof. Daneshmand and Prof. Mousavi were very active members of the IEEE Antennas and Propagation Society and the IEEE Microwave Theory and Techniques Society. We extend our condolences to their families and friends.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Compact Absorptive Filtering Patch Antenna
    • Authors: Yan-Ting Liu;Kwok Wa Leung;Nan Yang;
      Pages: 633 - 642
      Abstract: This article presents a compact absorptive filtering patch antenna. It consists of a filtering patch antenna and a bandstop filter (BSF), with their transfer functions being complementary to each other. A slot is fabricated in each of the patch and ground, giving a total of two radiation nulls for the lower bandedge. By using a dual-stub feed, two radiation nulls are also obtained for the upper bandedge. For the BSF, a λg/2 defected ground structure (DGS) and a λg/4 defected microstrip structure (DMS) are used in the design. It is terminated by a chip resistor. Since the filtering patch antenna and BSF have complementary transfer functions, the incident energy can be radiated effectively in the passband but largely absorbed by the resistor in the stopbands. As a result, only little energy will be reflected over a wide frequency range, giving a reflectionless characteristic. To demonstrate this idea, an absorptive filtering antenna operating at 5.8 GHz was designed, fabricated, and tested. Its impedance is matched from 5 to 6.5 GHz, with the measured out-of-band suppression being higher than 17 and 20 dB for the lower and upper stopbands, respectively. The measured peak realized gain is 7.28 dBi.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Rigorous Evaluation of Losses in Uniform Leaky-Wave Antennas
    • Authors: Walter Fuscaldo;
      Pages: 643 - 655
      Abstract: General formulas are proposed for thoroughly evaluating the radiation efficiency of traveling-wave antennas operating in any radiating regime. Indeed, existing theoretical models only work in the scanned-beam region, where the radiating mode is considerably above cutoff and the perturbation method applies. The analysis provided here extends the application of the perturbation method close to the cutoff condition, thus providing a correct estimation of the losses even in the case of broadside radiation. This case is particularly important for Fabry-Perot cavity leaky-wave antennas (FPC-LWAs) based on partially reflecting screens (PRSs), which are commonly designed to generate a broadside pencil beam. However, the previous works on FPC-LWAs always assume either a lossless PRS, or a lossless dielectric cover layer thus neglecting metal and dielectric losses: a hypothesis that is no longer fulfilled at high frequencies, such as millimeter-wave and submillimeter-wave frequencies. An original theoretical framework is thus developed to derive analytical formulas for a rigorous evaluation of losses when either lossy PRS or lossy dielectric cover layers are employed. Interestingly, the equivalence between a lossy PRS and a lossy dielectric cover layer is shown from a theoretical viewpoint. All the findings derived here are validated through full-wave simulations to corroborate the proposed analysis.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Longitudinally Slotted SIW Leaky-Wave Antenna for Low Cross-Polarization
           Millimeter-Wave Applications
    • Authors: Dongze Zheng;Yue-Long Lyu;Ke Wu;
      Pages: 656 - 664
      Abstract: A longitudinally slotted TE20-mode-driven substrate integrated waveguide (SIW) leaky-wave antenna (LWA) with low side-lobe and low cross-polarization is proposed and presented for millimeter-wave applications. In this work, a pair of long slots is etched symmetrically on the top broadside of an SIW working in the TE20 mode. With the odd-symmetry of TE20 mode field distribution, the even-symmetrically etched long slots paired along the centerline of the SIW have aperture fields of the same direction, thereby resulting in a constructive superposition of radiation. Thanks to these long slots with a meandering shape that is designed according to a specific aperture amplitude illumination (e.g., -35 dB Taylor line-source distribution) and their even-symmetry with respect to the centerline of the SIW, both low side-lobe and low cross-polarization are simultaneously achieved. Two meandering schemes with respect to the centerline of the SIW are adopted and, thus, two types of the designed LWAs are developed. For experimental prototypes of the proposed LWAs, a 3 dB directional coupler and a 90° phase shifter are combined together to excite the desired TE20 mode of the SIW. The proposed two types of LWAs are modeled, simulated, and fabricated. Both the simulated and measured results are in a good agreement.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Low-Profile Wideband Hybrid Metasurface Antenna Array for 5G and WiFi
    • Authors: Nian-Sheng Nie;Xue-Song Yang;Zhi Ning Chen;Bing-Zhong Wang;
      Pages: 665 - 671
      Abstract: A hybrid metasurface (HMS) is proposed to form a low-profile wideband antenna array. The antenna element is an array of 4 × 4 square metal patches and fed by a 50 Ω microstrip line through an H-shaped coupling slot on the ground plane. Only are the edge patches of HMS antenna element grounded by shorting pins for the suppression of surface waves and crosspolarization levels as well as the enhancement of the gain. With the HMS antenna element, a compact 2 χ 2 array with an overall size of 1.58λ0× 1.58λ0 ×0.068λ0 (λ4 is the free-space wavelength at 5.0 GHz) is designed, where the adjacent elements share the edge patches of the elements. The measurement shows the impedance bandwidth of 28% (4.41-5.85 GHz) for S11 ≤ -10 dB is obtained, and the boresight gain is greater than 8.4 dBi across the operating band, covering both fifth-generation (5G) sub 6 GHz and WiFi bands.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Low-Profile and High-Gain Frequency Beam Steering Subterahertz Antenna
           Enabled by Silicon Micromachining
    • Authors: Adrian Gomez-Torrent;María García-Vigueras;Laurent Le Coq;Adham Mahmoud;Mauro Ettorre;Ronan Sauleau;Joachim Oberhammer;
      Pages: 672 - 682
      Abstract: A very low-profile sub-THz high-gain frequency beam steering antenna, enabled by silicon micromachining, is reported for the first time in this paper. The operation bandwidth of the antenna spans from 220 to 300 GHz providing a simulated field of view of 56°. The design is based on a dielectric filled PPW leaky-wave antenna fed by a pillbox. The pillbox, a two-level PPW structure, has an integrated parabolic reflector to generate a planar wave front. The device is enabled by two extreme aspect ratio, 16 x 16 mm large perforated membranes, which are only 30 μm thick, that provide the coupling between the two PPWs and form the LWA. The micromachined low-loss PPW structure results in a measured average radiation efficiency of -1 dB and a maximum gain of 28.5 dBi with an input reflection coefficient below -10 dB. The overall frequency beam steering frontend is extremely compact (24 x 24 x 0.9 mm) and can be directly mounted on a standard WM-864 waveguide flange. The design and fabrication challenges of such high performance antenna in the sub-THz frequency range are described and the measurement results of two fabricated prototypes are reported and discussed.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Miniaturized RFID Reader Antennas Based on CRLH Negative Order Resonance
    • Authors: Zhan Wang;Yuandan Dong;
      Pages: 683 - 696
      Abstract: This article presents a type of miniaturized high-efficiency patch antennas for UHF radio frequency identification (RFID) reader applications based on the composite right-/left-handed (CRLH) negative order resonance. Miniaturization is achieved by using the first negative order resonance (-1st mode). These proposed CRLH resonators are realized by etching gap on the patch surface, which acts as a series left-handed (LH) capacitor as well as an effective radiator, and using metallic screws on the corner as steadying posts while also providing an LH inductor. Different from the traditional mushroom structures, these screws are placed on the two sides or corner of the unit cells allowing unobstructed current and field flowing inside the cavity. This enhances the quality factor and radiation efficiency. In addition, only metallic sheets, screws, and one thin substrate are used in the design, therefore dielectric loss is basically eliminated. Overall, these proposed antennas achieve a miniaturized size, as well as a high gain and radiation efficiency. The radiation characteristics of these RFID antennas are similar to the conventional patch antennas due to the -1st-order operation. Four antennas, including linearly polarized, circularly polarized (CP), frequency-tunable, and polarization/frequency-reconfigurable antennas, are carefully designed, investigated, and experimentally verified. Remarkable agreement has been observed between simulation and measurement. These antennas well cover 902-928 MHz UHF band. RF range tests are carried out for application verification. They demonstrate a compact size, low-cost, low-loss, and high efficiency with easy implementation. The CP antennas exhibit a good bandwidth and an excellent axial ratio in the whole upper semisphere. They have been selected for mass production, which illustrates a good engineering application example of CRLH metamaterial antennas.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Dynamic Dual Tapered 3-D Printed Nested Helical Antenna
    • Authors: Youssef Tawk;
      Pages: 697 - 702
      Abstract: In this article, a new 3-D printed dual tapered nested antenna design is presented. The antenna is composed of two tapered helical arms that wrap around each other in opposite orientations to exhibit orthogonal circular polarization schemes. The nested tapered helices are 3-D laser printed with copper platting. The outer helical arm is tailored to resonate at 2.4 GHz, while the inner arm is designed for operation at 5.4 GHz. The overall antenna structure is then arranged as an array of elements that can dynamically alter its lattice in either linear or triangular topologies in order to achieve reconfiguration in the radiation pattern. The change in topologies is driven by programmable robots that can reshape the antenna array's radiation pattern dynamically and on demand. The whole system is measured and tested for various arrangements where the measured results show good agreement with the simulated data.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Two-Dimensional Pattern-Reconfigurable Cross-Slot Antenna With Inductive
           Reflector for Electromagnetic Torso Imaging
    • Authors: Amin Darvazehban;Sasan Ahdi Rezaeieh;Omid Manoochehri;Amin M. Abbosh;
      Pages: 703 - 711
      Abstract: A wideband and low-profile cross-slot pattern reconfigurable antenna for electromagnetic imaging systems is proposed. The antenna is designed to cover the human chest area with steerable unidirectional radiation patterns at 0.7-0.9 GHz. The antenna is comprised of a corrugated cross-slot as the main radiator, and four parasitic slots with four p-i-n diodes operating as reflectors. An embedded feeding network with six p-i-n diodes is used to feed the main slot and switch the feeding path to modify the direction of the radiated beam (vertical/horizontal). In addition, an inductive mesh-grid surface is used to reduce the back lobe and enhance the operating frequency bandwidth. The antenna dimensions are 0.8λ0×0.8λ0×0.18λ0 (where λ0 is the wavelength of the lowest frequency operation). By turning the parasitic slot p-i-n diodes to ON/OFF modes, the main beam can be steered along five distinctive positions at 0°, and at ±30° in two perpendicular planes. The antenna achieves a peak gain of 9 dBi at 0.8 GHz with 1 dB gain variations over the band of operation with a peak front-to-back ratio of 20 dB.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Miniaturized Triple-Band Highly Transparent Antenna
    • Authors: Reza Yazdani;Mahdi Yousefi;Hadi Aliakbarian;Homayoon Oraizi;Guy A. E. Vandenbosch;
      Pages: 712 - 718
      Abstract: In this article, a novel on-glass antenna which is transparent, miniaturized, and multiband is presented. First, the antenna achieves more than 80% transparency. This is realized by removing as much as possible the metal pattern, without compromising the operational electric current flow. Second, the antenna is electrically small, $0.13lambda times 0.19lambda $ at 0.95 GHz. This is realized by choosing a proper topology for the remaining metal pattern. Third, the antenna is triple band, covering the ranges 0.88-1.03 GHz, 1.47-2.74 GHz, and 3.32-5.97 GHz. The radiation is omnidirectional in all bands, which is suitable for GSM900/1800, 3G, 4G, 5G (2.55-2.65 GHz), WLAN (2.4/5.2/5.8 GHz), and WiMAX (2.5/5.5 GHz). The maximum gain in the three bands is equal to -0.18, 3.66, and 4.35 dBi with corresponding radiation efficiencies of 66%, 87%, and 88%. A prototype is made by first printing a metallic circuit on a thin FR-4 substrate and then gluing it on a glass substrate. The measurement results are in good agreement with simulations.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Metasurface Lens for Ultra-Wideband Planar Antenna
    • Authors: Omer Yesilyurt;Gonul Turhan-Sayan;
      Pages: 719 - 726
      Abstract: In this article, an ultra-wideband metasurface lens is designed and integrated into an antipodal Vivaldi antenna (AVA) to improve its radiation directivity without affecting its efficiency and return loss characteristics. The metasurface lens consists of high permittivity metamaterial unit cells which resonate at frequencies far away from the operation bandwidth of 1-6 GHz. Electric field distributions of the antennas show that the near-field behaves more planar for the metasurface lens loaded AVA, as compared to conventional AVA. Both the original antenna and the newly proposed antenna are simulated, fabricated, and tested. The measurements are found in very good agreement with the simulation results. In the operation bandwidth of 1-6 GHz, the return loss is less than -10 dB for both antennas. As verified by far-field measurements, the metasurface loaded AVA has achieved higher gain in the operation bandwidth. Additionally, the half power beamwidth of the AVA is significantly reduced by the inclusion of the metasurface lens.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • ${X}$+ -Band+and++$Ka$+ -Band&rft.title=IEEE+Transactions+on+Antennas+and+Propagation&rft.issn=0018-926X&rft.date=2020&rft.volume=68&rft.spage=727&rft.epage=735&rft.aulast=Freebury;&rft.aufirst=Nacer&rft.au=Nacer+Chahat;Jonathan+Sauder;Matthew+Mitchell;Neal+Beidleman;Gregg+Freebury;">One-Meter Deployable Mesh Reflector for Deep-Space Network
           Telecommunication at ${X}$ -Band and $Ka$ -Band
    • Authors: Nacer Chahat;Jonathan Sauder;Matthew Mitchell;Neal Beidleman;Gregg Freebury;
      Pages: 727 - 735
      Abstract: This article presents the design and optimization of a deployable 1 m mesh reflector compatible with a 12U-class CubeSat. This antenna is designed for telecommunication and is compatible with NASA's deep-space network (DSN) at X-band (i.e., uplink: 7.145-7.19 GHz; downlink: 8.4-8.45 GHz) and Ka-band frequencies (i.e., uplink: 34.2-34.7 GHz; downlink: 31.8-32.3 GHz). Three right-handed circularly polarized (RHCP) antennas, both transmit and receive, are introduced here: X-band only, Ka-band only, and X-/Ka-band. For the X-band-only antenna, a gain of 36.1 and 36.8 dBic is achieved at uplink and downlink frequency bands, respectively. This translates into an aperture efficiency of 72% and 62%. For the Ka-band-only antenna, a gain of 48.4 and 48.7 dBic is obtained at downlink and uplink frequency bands, which translate into an aperture efficiency of 62% and 72%, respectively.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Novel E-plane-Focused Cylindrical Luneburg Lens Loaded With Metal Grids
           for Sidelobe Level Reduction
    • Authors: Pengfei Liu;Xiao-Wei Zhu;Yan Zhang;Zhi Hao Jiang;Xiang Wang;Wei Hong;Trong Hieu Le;
      Pages: 736 - 744
      Abstract: A novel cylindrical Luneburg lens operating at 26 GHz-band using hole drilling technology are reported, aiming at proper radiation patterns. The cylindrical Luneburg lens antenna converge microwaves in the plane perpendicular to the generatrix of the cylinder. An E-plane-focused cylindrical Luneburg lens antenna with the thickness of 20 mm and diameter of 88.2 mm is proposed for working at 26 GHz. Feed of the lens antenna is a conventional rectangular waveguide. Furthermore, in order to compensate the phase of the microwave in the nonconverging plane (H-plane in this case), a pair of printed circuit boards (PCBs) etched with particular metal grids is attached to the side faces of the lens. With optimized design for the grids, a narrower beam is obtained in the H-plane while the sidelobe level (SLL) of the cylindrical Luneburg lens could be drastically reduced compared with lens antenna without the special metal grids. Measured results of the fabricated lens antennas are in a good agreement with the simulation, proving its effectiveness and practicability that the designed grids benefit the radiation pattern performances. With an appropriate pattern for the H-plane achieved, proposed cylindrical Luneburg lens operating at millimeter-wave (mmW) band is a suitable candidate for multibeam communication systems.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Wideband Circularly Polarized 3-D Printed Dielectric Rod Antenna
    • Authors: Jin Huang;Shengjian Jammy Chen;Zhenghui Xue;Withawat Withayachumnankul;Christophe Fumeaux;
      Pages: 745 - 753
      Abstract: This article presents a 3-D-printed dielectric rod antenna with wideband circular polarization. The proposed dielectric device comprises two main components: a launching part and a radiating part. The launching part consists of three cylindrical sections with stepped permittivity for wideband impedance matching to the rectangular waveguide feed. The radiating part is a tapered dielectric rod with two helical grooves that generate circular polarization. The experimental results verify that the proposed antenna exhibits a wide impedance bandwidth of 60.3% from 4.05 to 7.55 GHz, a wide 3 dB axial ratio bandwidth of 57.0% from 4.20 to 7.55 GHz, a high realized gain varying within 8.3 and 11.5 dBiC over the whole band, and the desired stable endfire radiation patterns. The 3-D printing technology provides a viable approach to realization of the proposed complicated geometry in a single piece with high accuracy and great flexibility.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Bow-Tie-Shaped Radiating Element for Single and Dual Circular Polarization
    • Authors: Eduardo Garcia-Marin;José Luis Masa-Campos;Pablo Sanchez-Olivares;Jorge A. Ruiz-Cruz;
      Pages: 754 - 764
      Abstract: A fully metallic radiating element is presented in this article for single and dual circular polarization applications. The shape of the radiating element corresponds to a bow-tie-shaped field rotator designed to generate two orthogonal modes in quadrature as a basis for circular polarization. The bow-tie-shaped basic element is able to provide low axial ratio with a compact, easy-to-manufacture profile. In addition, it allows diverse ways of operation: feeding through a rectangular waveguide provides single circular polarization, while square waveguide is used for dual circular polarization. The radiating element has been designed at the Ku band and validated by the competitive experimental results. In the case of single circular polarization, over 21% bandwidth has been obtained under 15 dB return loss and 3 dB axial ratio criteria, with a radiating element height of 0.75λ0 (free-space wavelength) at 18 GHz. The dual circularly polarized version achieves 18.3% bandwidth when 15 dB return loss and 3 dB axial ratio are established. In this case, the required antenna height is slightly higher than λ0 at 18 GHz.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Compact Magnetic Loop Antenna for Omnidirectional On-Metal UHF Tag Design
    • Authors: Shin-Rou Lee;Wai-Hau Ng;Eng-Hock Lim;Fwee-Leong Bong;Boon-Kuan Chung;
      Pages: 765 - 772
      Abstract: For the first time, a planar and low-profile magnetic loop antenna is proposed for designing an omnidirectional metalmountable radio frequency identification (RFID) tag antenna. The proposed tag antenna, which consists of an annular slot exciter, a shorted patch, two shorting stubs, and four notches, can be easily made on one side of a flexible polyimide film. It has a dimension of 38 mm × 38 mm × 1.6 mm (0.116λ x 0.116λ x 0.0049λ). The tag antenna is able to generate stable omnidirectional read patterns when placed on metal. The notches are not only employed for bringing down the tag's resonant frequency to the ultrahigh (UHF) RFID band, but they can also be used for effectively reducing the gain fluctuation in the azimuth plane. Good maximum power transmission of ~90% is attainable. Measurements are conducted with reference to a transmitting power of 4W EIRP, and it has been shown that the proposed tag antenna is able to generate omnidirectional radiation patterns with a stable read distance of 5.29-5.65 m on metal in all directions in the azimuth plane. The tag's resonant frequency is also very stable with a maximum fluctuation of only 0.22%.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Fundamental Bounds on Transmission Through Periodically Perforated Metal
           Screens With Experimental Validation
    • Authors: Andrei Ludvig-Osipov;Johan Lundgren;Casimir Ehrenborg;Yevhen Ivanenko;Andreas Ericsson;Mats Gustafsson;B. L. G. Jonsson;Daniel Sjöberg;
      Pages: 773 - 782
      Abstract: This article presents a study of transmission through arrays of periodic sub-wavelength apertures. Fundamental limitations for this phenomenon are formulated as a sum rule, relating the transmission coefficient over a bandwidth to the static polarizability. The sum rule is rigorously derived for arbitrary periodic apertures in thin screens. By this sum rule we establish a physical bound on the transmission bandwidth which is verified numerically for a number of aperture array designs. We utilize the sum rule to design and optimize sub-wavelength frequency selective surfaces with a bandwidth close to the physically attainable. Finally, we verify the sum rule and simulations by measurements of an array of horseshoe-shaped slots milled in aluminum foil.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • $S$+ -/+$C$+ -Band+Antenna+Array+With+Dual+Polarization+and+Modularity&rft.title=IEEE+Transactions+on+Antennas+and+Propagation&rft.issn=0018-926X&rft.date=2020&rft.volume=68&rft.spage=783&rft.epage=794&rft.aulast=Gong;&rft.aufirst=Mahmoud&rft.au=Mahmoud+Shirazi;Junyi+Huang;Tianjiao+Li;Xun+Gong;">A Switchable $S$ -/ $C$ -Band Antenna Array With Dual Polarization and
    • Authors: Mahmoud Shirazi;Junyi Huang;Tianjiao Li;Xun Gong;
      Pages: 783 - 794
      Abstract: A switchable S-/C-band antenna array is presented with dual polarization and modularity. A 2 × 2 S-band antenna array can be reconfigured into a 4 × 4 C-band antenna array within the same physical aperture. A narrow ground strip inside the slot-ring antenna is used to reduce the mutual coupling between antenna elements and suppress the null in the radiation patterns in the C-band array. In addition, the vertical coaxial-tomicrostrip transition allows for feeding the antenna array from behind the ground plane, making it modular. Dual polarization capability is achieved in each band. This antenna array shows 64.3% and 66.7% fractional bandwidth with 8.4 and 14.3 dBi gain in the Sand C-band operating states, respectively. The isolation between different antenna ports, radiation patterns at different frequency points, and input third-order intermodulation product of the antenna is measured. A triangular lattice is implemented for the S-band array to minimize the physical spacing between the antenna elements, and therefore enable beam steering to large angles.angles.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Miniaturized Dual-Band Dual-Polarized Band-Notched Slot Antenna Array
           With High Isolation for Base Station Applications
    • Authors: Min Li;Rong Wang;Jamal Muhammad Yasir;Lijun Jiang;
      Pages: 795 - 804
      Abstract: In this article, a miniaturized dual-band dual-polarized slot antenna array is proposed for base station applications. It consists of two closely located $1 times 4$ subarrays for the digital cellular system (DCS) and wideband code division multiple access (WCDMA) operations. The band-notched slot antenna (BNSA) is designed and adopted as the subarray element with radiation-suppression characteristic at notch frequencies. The notch frequency for one subarray is designed at the center operating frequency of the other subarray. As a result, the radiation from DCS subarray could be effectively suppressed within the WCDMA band and vice versa, resulting in high isolation between two subarrays with a small separation distance. By using the artificial magnetic conductor (AMC) reflector, the array height could be reduced by half, as compared with the perfect electric conductor (PEC) counterpart. In addition, a four-way unequal power divider is designed for the array's beam-pattern synthesis. For the demonstration, the proposed array is fabricated and measured. The measurement results show that the dual-band array achieves the impedance bandwidths of 1.65-1.88 and 1.89-2.22 GHz, the isolations over 25 dB, the realized boresight gains of 12.2-12.8 and 12.3-13.2 dBi, and the sidelobe levels below -18 dB. The results indicate that the proposed array is a promising candidate for base-station applications.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • High-Gain Filtering Reflectarray Antenna for Millimeter-Wave Applications
    • Authors: Geng-Bo Wu;Yuan-Song Zeng;Ka Fai Chan;Bao-Jie Chen;Shi-Wei Qu;Chi Hou Chan;
      Pages: 805 - 812
      Abstract: This article presents a novel design of filtering reflectarray antenna, an integrated module for the combination of filtering and high-gain radiation performance. The filtering reflectarray consists of two-section metal pixel waveguide elements, which can realize the optimized aperture reflection phase distributions in the operating band f1 ≤ f ≤ f2 to yield high-gain radiation. Below the lower cutoff frequency f1, the reflection phase distributions drastically deviate from the required ones. Above the upper cutoff frequency f2, both the amplitude and phase distributions fail to provide strong coherent radiation. In the reflectarray synthesis process, a multi-frequency phase matching method (PMM) is further developed, in which the phase compensation for each pixel is implemented at three simultaneous in-band frequencies. Meanwhile, the effects of incident angle for elements are also taken into consideration during the reflectarray synthesis. The design of an 11λ× 11λ filtering reflectarray operating from 55 to 65 GHz was conveniently fabricated by 3-D printing technology, followed by metal coating with advantages of rapid prototyping, lightweight, and low cost. Both the simulated and measured results show that the proposed reflectarray can realize high-gain radiation within the desired frequency band but presents effective suppression of out-of-band signals, demonstrating its filtering capability.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Low-Profile Light-Weight Wideband Connected Parallel Slot Array for
           Wide-Angle Scanning
    • Authors: Yan Li;Shaoqiu Xiao;Chang-Hai Hu;Zhixin Yao;
      Pages: 813 - 823
      Abstract: A novel wideband-connected parallel slot array for wide-angle scanning applications is proposed in this article. Different from conventional connected slot arrays, the proposed array consists of dual parallel slots, where the introduced parasitic slot acts as an additional series capacitor. The connected parallel slot array can realize low and moderate active input impedances and achieve wide bandwidth without using any complex balun. To improve the wide-angle impedance matching issue and avoid an increase in the array profile, a mixed periodic metallic strips layer with almost zero height and weight was adopted. The metallic strips layer can be regarded as a shunt capacitance between the array and free space. Additionally, equivalent circuit models were established to analyze the function of the introduced parasitic slot and metallic strips layer. The proposed connected parallel slot array achieves a concurrent bandwidth of approximately 69.2% (1.35-2.78 GHz), while covering a scanning area of ±60° in the E-, H-, and D-planes. The profile is only 0.088 λL, where λL is the wavelength of the lowest operation frequency in free space. Besides, low cross-polarization in principal planes, planar and simple structure, and light weight are also the merits of the proposed antenna array.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Complete and Unified Time- and Frequency-Domain Study on 4-D Antenna
           Arrays Including Mutual Coupling Effect
    • Authors: Feng Yang;Shiwen Yang;Weijun Long;Yikai Chen;Fang Wang;Shiwei Qu;
      Pages: 824 - 837
      Abstract: A complete and unified time- and frequency-domain study on 4-D antenna arrays including mutual coupling effect is presented in this article. The “instantaneous” active reflection coefficient (ARC) or power pattern as a function of time and the “averaged” ARC or power pattern as a function of frequency are introduced to evaluate the port matching and the mutual coupling in 4-D arrays, respectively. The two analysis approaches from different viewpoints are demonstrated to be unified and complementary through Fourier transform. Based on the Fourier transform, five unified equations corresponding to the power pattern, ARC, input power, reflected power, and radiated power are shown to explain the working principle of 4-D arrays from time domain and frequency domain. Other antenna parameters including directivity, efficiency, and gain are also thoroughly investigated. A novel optimization method is proposed to synthesize a 16-element 4-D linear array with tightly coupled elements, and the results are used to validate the five unified equations and illustrate its working principle. Moreover, an S-band eight-element 4-D linear array is constructed and measured to demonstrate these studies.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Self-Curing Decoupling Technique for MIMO Antenna Arrays in Mobile
    • Authors: Jiangwei Sui;Yuhang Dou;Xide Mei;Ke-Li Wu;
      Pages: 838 - 849
      Abstract: The self-curing decoupling technique is substantially extended to apply to multi-input multi-output (MIMO) antenna arrays in mobile terminals. Using this proposed technique, the mutual coupling between antennas can be reduced by inlaying lumped element capacitors on the ground plane. The decoupling method does not require any physical connection or obstruction between coupled antennas. The significance of the proposed decoupling technique is fourfold: 1) it works for inverted-F antennas (IFAs), monopole antennas, and loop antennas, the most three commonly used antenna forms for mobile terminals; 2) the inherent improvement on matching conditions after decoupling; 3) the flexibility in implementation owing to its detachment from the antenna body; and 4) the applicability to an array with more than two elements. Four demonstrating examples, including two IFAs, two monopole antennas, two loop antennas, and a MIMO array with four elements of different antenna types are studied by EM modeling, passive tests, and MIMO over-the-air (OTA) measurements. The experimental results show that significant improvements in port isolation (from 9 to 30 dB), total efficiency (from 53% to 69%), and above all, the system data throughput can be achieved. The working mechanism of the method is revealed and justified through the partial element equivalent circuit (PEEC) model in the fifth example.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • $S$+ -Parameter+Characterization&rft.title=IEEE+Transactions+on+Antennas+and+Propagation&rft.issn=0018-926X&rft.date=2020&rft.volume=68&rft.spage=850&rft.epage=858&rft.aulast=Marnat;&rft.aufirst=Laurent&rft.au=Laurent+Dussopt;Kossaila+Medrar;Loïc+Marnat;">Millimeter-Wave Gaussian-Beam Transmitarray Antennas for Quasi-Optical $S$
           -Parameter Characterization
    • Authors: Laurent Dussopt;Kossaila Medrar;Loïc Marnat;
      Pages: 850 - 858
      Abstract: This article presents the design and demonstration of Gaussian-beam transmitarray antennas at millimeter-wave frequencies. The main design tradeoffs and theoretical performances are first investigated numerically. Next, two antenna prototypes are designed in V-band and fabricated in printedcircuit-board technology. These prototypes are validated experimentally through transmission measurements in face-to-face configuration (Gaussian coupling) and near-field measurements. Experimental results are in good agreement with simulations predicting a Gaussian efficiency better than 90% and an antenna efficiency of 61.2% at 61.5 GHz. Near-field measurements demonstrate a Gaussian field distribution and a nearly planar wavefront in the focal plane at 57-66 GHz. Finally, the Gaussian beam transmitarrays are demonstrated in a V-band quasioptical vectorial S-parameter measurement setup. Transmitarray unit-cells are characterized in reflection and transmission at 50-70 GHz and experimental results exhibit a very good agreement with simulations.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • $Ka$+ -Band+Applications&rft.title=IEEE+Transactions+on+Antennas+and+Propagation&rft.issn=0018-926X&rft.date=2020&rft.volume=68&rft.spage=859&rft.epage=872&rft.aulast=Hong;&rft.aufirst=Zhi&rft.au=Zhi+Hao+Jiang;Yan+Zhang;Jun+Xu;Yingrui+Yu;Wei+Hong;">Integrated Broadband Circularly Polarized Multibeam Antennas Using
           Berry-Phase Transmit-Arrays for $Ka$ -Band Applications
    • Authors: Zhi Hao Jiang;Yan Zhang;Jun Xu;Yingrui Yu;Wei Hong;
      Pages: 859 - 872
      Abstract: In this article, integrated millimeter-wave (mmW) broadband circularly polarized (CP) single-beam/multibeam antennas (MBAs) are reported. The antennas comprised a Berryphase (BP) transmit-array (TA) containing three layers of slotted elliptical metallic resonator arrays and a cluster of substrate integrated waveguide (SIW) -fed CP source radiators with an anisotropic impedance surface (AIS) superstrate. By utilizing broadband mmW CP radiators, BP-based transmission phase compensation, and tailoring the dispersive transfer function of the TA cell, broadband CP high-gain beams can be generated with improved gain flatness and an antenna profile of only 2.6λ0. Moreover, by employing multifocal strategies in the design of TAs, the scanning loss for the multifeed MBAs can be alleviated, expanding their range of coverage. Two Ka-band prototypes were fabricated and characterized. The single-feed single-beam antenna experimentally achieves a peak gain of 22.6 dBic and a 2 dB gain bandwidth of 20.7%, within which the S11 is below -10 dB and axial ratio (AR) is smaller than 3 dB. The second prototype, which contains five source radiators and a bifocal TA, generates five pencil beams that cover a range between ±33°. It features a peak broadside gain of 22.2 dBic, a joint AR
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Conformal Circularly Polarized Series-Fed Microstrip Antenna Array
    • Authors: Stanislav Ogurtsov;Slawomir Koziel;
      Pages: 873 - 881
      Abstract: A conformal circularly polarized (CP) series-fed microstrip array design for broadside radiation is presented. The array aperture under design is conformal to a cylindrical surface of a given radius. The approach we present primarily addresses focusing of the CP major lobe of the conformal array by proper dimensioning of the aperture spacings. The proposed analytical models yield the values of the element spacings within the series-fed conformal array aperture and element-specific spacings of the patch radiators within each CP element. These spacings are critical to produce a broadside CP major lobe at the design frequency. Subsequently, each array element is equipped with an in-line matching quarter wave transformer. The measured characteristics of the X-band conformal array validate the proposed design approach.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Compact Beam-Scanning Flat Array Based on Substrate-Integrated Waveguide
    • Authors: Houtong Qiu;Xue-Xia Yang;Yingjie Yu;Tian Lou;Zhangfei Yin;Steven Gao;
      Pages: 882 - 890
      Abstract: A compact beam-scanning flat antenna array with high gain based on the substrate- integrated waveguide (SIW) is presented in this article. The radiation elements are the continuous transverse stub (CTS) constructed by SIW, which are arrayed on the substrate. The SIW-CTS array has a 4 dB higher gain than the traditional CTS array with the metal parallel plate waveguide and the theoretical explanation is analyzed. A new compact corporate-feed network consisting of an SIW-horn and a flat lens is also proposed. The flat lens could convert the cylindrical wavefront generated by the feed probe and the SIW-horn to a planar wavefront for feeding the CTS array. The Taylor distribution of the feed level made the array has a low sidelobe and high gain. The beam scanning of the array could be realized by simply moving the small SIW-horn along the line across the focal point. An eight-element array is designed, simulated, and fabricated to verify the design. The measured results show that the scanning range is from -35° to 35° with the highest gain of being 20.6 dBi and the sidelobe level of -25.2 dB at the broadside.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • An Integrated Coding-Metasurface-Based Array Antenna
    • Authors: Peng Xu;Wei Xiang Jiang;Xiao Cai;Shi Hao Bai;Tie Jun Cui;
      Pages: 891 - 899
      Abstract: We present a novel antenna based on 2 bit digital coding metasurface and perform convolution operations on the coding antenna to manipulate the radiation waves. Different from the conventional array antennas, we propose to use the metasurface to change the radiation phase of elementary antenna (EA) in a more modular and simpler manner. The radiation beams can be arbitrarily controlled by designing the 2 bit digital coding sequence, and the center operating frequency of the coding antenna is designed at 7.29 GHz. The experimental results of the fabricated prototype antenna show good agreement with the numerical simulations. The proposed 2 bit coding antenna has been demonstrated to possess the capability of achieving beam deflection, multibeam, and perform Fourier operations on the coding antenna. This article raises a new design method of antenna array to control radiation beams.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Towards a Low-SWaP 1024-Beam Digital Array: A 32-Beam Subsystem at 5.8 GHz
    • Authors: Arjuna Madanayake;Viduneth Ariyarathna;Suresh Madishetty;Sravan Pulipati;Renato J. Cintra;Diego Coelho;Raíza Oliviera;Fábio M. Bayer;Leonid Belostotski;Soumyajit Mandal;Theodore S. Rappaport;
      Pages: 900 - 912
      Abstract: Millimeter-wave communications require multibeam beamforming to utilize wireless channels that suffer from obstructions, path loss, and multipath effects. Digital multibeam beamforming has maximum degrees of freedom compared to analog-phased arrays. However, circuit complexity and power consumption are important constraints for digital multibeam systems. A low-complexity digital computing architecture is proposed for a multiplication-free 32-point linear transform that approximates multiple simultaneous radio frequency (RF) beams similar to a discrete Fourier transform (DFT). Arithmetic complexity due to multiplication is reduced from the fast Fourier transform (FFT) complexity of O(N log N) for DFT realizations, down to zero, thus yielding a 46% and 55% reduction in chip area and dynamic power consumption, respectively, for the N = 32 case considered. This article describes the proposed 32-point DFT approximation targeting 1024 beams using a 2-D array and shows the multiplierless approximation and its mapping to a 32-beam subsystem consisting of 5.8 GHz antennas that can be used for generating 1024 digital beams without multiplications. Real-time beam computation is achieved using a Xilinx field-programmable gate array (FPGA) at 120 MHz bandwidth per beam. Theoretical beam performance is compared with measured RF patterns from both a fixed-point FFT and the proposed multiplier-free algorithm and is in good agreement.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Generalized Design Methodology of Mode Conversion Based on Transmissive
    • Authors: Jianing Zhao;Tianming Li;Hao Li;Yihong Zhou;Haiyang Wang;Biao Hu;Huan Zou;Qiao Liu;
      Pages: 913 - 918
      Abstract: A novel and generalized methodology of mode conversion based on the transmissive metasurfaces is studied in this article. The mathematic formulations, the design criterions, and procedures have been presented in detail. To further demonstrate the proposed methodology, four typical examples are designed. Subsequently, a prototype with the input mode of circular waveguide TM0,1 mode is designed, fabricated, and measured at X-band. The simulated and measured results show that the input mode has been converted into the Guassian-like mode, which could verify the correctness of the proposed design methodology. In addition, due to the rich applications of the transmissive metasurfaces, the proposed methodology will start a new page to realize the mode conversion, especially for the high-frequency case.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • ${N}$+ -Layer+Structure+by+the+Ray-Series+Method&rft.title=IEEE+Transactions+on+Antennas+and+Propagation&rft.issn=0018-926X&rft.date=2020&rft.volume=68&rft.spage=919&rft.epage=926&rft.aulast=Bute;&rft.aufirst=Ugur&rft.au=Ugur+Cem+Hasar;Musa+Bute;">Temporal Behavior of Plane Waves Within an ${N}$ -Layer Structure by the
           Ray-Series Method
    • Authors: Ugur Cem Hasar;Musa Bute;
      Pages: 919 - 926
      Abstract: The ray-series (RS) method, which is practically more tractable and feasible than the transfer matrix (TM) method for the time-domain analysis, is examined and applied for investigation of temporal reflection and transmission responses of an N-layer structure for a plane wave incidence. These responses are represented by reduced reflection and transmission coefficients associated with unit step functions with different effective time periods and weightings depending on electromagnetic properties of the layers constituting the N-layer structure. Numerical and simulation analyses in line with the residue theorem and Bromwich integral were performed to validate our formalism and practically demonstrate its applicability for temporal analysis.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Modal Tracking Based on Group Theory
    • Authors: Michal Masek;Miloslav Capek;Lukas Jelinek;Kurt Schab;
      Pages: 927 - 937
      Abstract: Issues in modal tracking in the presence of crossings and crossing avoidances between eigenvalue traces are solved via the theory of point groups. The von Neumann-Wigner theorem is used as a key factor in predictively determining mode behavior over arbitrary frequency ranges. The implementation and capabilities of the proposed procedure are demonstrated using characteristic mode decomposition as a motivating example. The procedure is, nevertheless, general and can be applied to an arbitrarily parametrized eigenvalue problem. A treatment of modal degeneracies is included and several examples are presented to illustrate modal tracking improvements and the immediate consequences of improper modal tracking. An approach leveraging a symmetry-adapted basis to accelerate computation is also discussed. A relationship between geometrical and physical symmetries is demonstrated on a practical example.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Time-Domain Electromagnetic-Field Transmission Between Small-Loop Antennas
           on a Half-Space With Conductive and Dielectric Properties
    • Authors: Martin Štumpf;Giulio Antonini;Ioan E. Lager;Guy A. E. Vandenbosch;
      Pages: 938 - 946
      Abstract: The pulsed EM-field signal transfer between two co-planar small-loop antennas located on a half-space with dielectric and conductive properties is analyzed analytically with the help of the Cagniard-DeHoop technique and the Schouten-Van der Pol theorem. The analysis yields a closed-form time-domain expression for the open-circuit voltage induced across the ports of the receiving antenna. Limiting cases considering the mutual coupling between two loops placed in free-space and on a dielectric half-space are discussed. The obtained results are validated using analytical expressions for the special cases and with the aid of a 3-D EM computational tool.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Fast Numerical Method for the Galvanic Measurement in Hydraulic Fracture
    • Authors: Yuan Fang;Yunyun Hu;Qiwei Zhan;Dezhi Wang;Runren Zhang;Qing Huo Liu;
      Pages: 947 - 957
      Abstract: Hydraulic fracturing is critical for unconventional oil and gas production. Recently, galvanic methods, including borehole-to-surface and surface-to-borehole electromagnetic methods, have been applied in hydraulic fracture evaluation. However, conventional computational electromagnetic methods require huge computational cost to simulate the common galvanic fracture model, which consists of a long cased borehole, 3-D thin fractures, and an underground stratified medium. More seriously, modeling both vertical and horizontal energized cased boreholes in layered media is exceptionally difficult. In this article, we present a hybrid numerical mode matching method with stabilized bi-conjugate gradient fast Fourier transform method (NMM-BCGS-FFT) as the forward solver to efficiently model 3-D fractures in the galvanic survey. Both vertical and horizontal energized cased boreholes are modeled in the forward solver. The numerical results show the accuracy and efficiency of the hybrid forward solver. The realistic field galvanic detection model analysis will show the practicability of the forward solver.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Fast 3-D Volume Integral Equation Domain Decomposition Method for
           Electromagnetic Scattering by Complex Inhomogeneous Objects Traversing
           Multiple Layers
    • Authors: Dezhi Wang;Yunyun Hu;Yuan Fang;Qiwei Zhan;Runren Zhang;Wei-Feng Huang;Qing Huo Liu;
      Pages: 958 - 966
      Abstract: In many applications, electromagnetic scattering from inhomogeneous objects embedded in multiple layers needs to be simulated numerically. The straightforward solution by the method of moments (MoM) for the volume integral equation method is computationally expensive. Due to the shift-invariance and correlation properties of the layered-medium Green's functions, the stabilized-biconjugate gradient fast Fourier transform (BCGS-FFT) has been developed to greatly reduce the computational complexity of the MoM, but so far this method is limited to objects located in a homogeneous background or in the same layer of a layered medium background. For those problems with objects located in different layers, FFT cannot be applied directly in the direction normal to the layer interfaces, thus the MoM solution requires huge computer memory and CPU time. To overcome these difficulties, the BCGS-FFT method combined with the domain decomposition method (DDM) is proposed in this article. With the BCGS-FFT-DDM, the objects or different parts of an object are first treated separately in several subdomains, each of which satisfies the 3-D shift-invariance and correlation properties; the couplings among the different objects/parts are then taken into account, where the coupling matrices can be built to satisfy the 2-D shift-invariance property if the objects/subdomains have the same mesh size on the xy plane. Hence, 3-D FFT and 2-D FFT can respectively be applied to accelerate the selfand mutual-coupling matrix-vector multiplications. By doing so, the impedance matrix is explicitly formed as one including both the selfand mutual-coupling parts, and the solver converges well for problems with considerable conductivity contrasts. The computational complexity in memory and CPU time for self-coupling matrix-vector multiplication are O(Nzq Nx Ny) and O(NzNx Ny log(NzNx Ny)) respectively, and for mutual-coupling matrix-vector multiplication are O(NpzpNzqNxNy) and O(NzpNzqNxNylog(NxNy)), respectively, for the proposed method, where Nx and Ny are the cell numbers of all the subdomains in the xand y-directions, and Nzp and Nzq the cell numbers of different subdomains in the z-direction. Several results of different subsurface sensing scenarios are presented to show the capabilities of this method.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Automatic Localized Nonconformal Mesh Refinement for Surface Integral
    • Authors: Jorge A. Tobon Vasquez;Zhen Peng;Jin-Fa Lee;Giuseppe Vecchi;Francesca Vipiana;
      Pages: 967 - 975
      Abstract: We propose an automatic, solution based, localized meshing refinement for increasing the accuracy of integral-equation solution for multi-scale electromagnetic problems. The procedure starts with a local measure of the boundary condition error, via testing on zero-order basis functions defined on the finest level mesh. Then, the adaptive mesh refinement (h-refinement) is obtained by nonconformal submeshing with Discontinuous Galerkin formulation in order to achieve the desired accuracy. Numerical experiments show the effectiveness of the approach in the cases of cubic geometry and realistic multi-scale structures.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Large Time Step and DC Stable TD-EFIE Discretized With Implicit
           Runge–Kutta Methods
    • Authors: Alexandre Dély;Francesco P. Andriulli;Kristof Cools;
      Pages: 976 - 985
      Abstract: The time domain-electric field integral equation (TD-EFIE) and its differentiated version are widely used to simulate the transient scattering of a time dependent electromagnetic field by a perfect electric conductor (PEC). The time discretization of the TD-EFIE can be achieved by a space-time Galerkin approach or, as it is considered in this contribution, by a convolution quadrature using implicit Runge-Kutta methods. The solution is then computed using the marching-on-in-time (MOT) algorithm. The differentiated TD-EFIE has two problems: 1) the system matrix suffers from ill-conditioning when the time step increases (low frequency breakdown) and 2) it suffers from the DC instability, i.e., the formulation allows for the existence of spurious solenoidal currents that grow slowly in the solution. In this article, we show that 1) and 2) can be alleviated by leveraging quasi-Helmholtz projectors to separate the Helmholtz components of the induced current and rescale them independently. The efficacy of the approach is demonstrated by numerical examples including benchmarks and real-life applications.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Spectral Numerical Mode-Matching Method for 3-D Layered Multiregion
    • Authors: Jie Liu;Na Liu;Qing Huo Liu;
      Pages: 986 - 996
      Abstract: The spectral numerical mode-matching (SNMM) method is developed to simulate the 3-D layered multiregion structures. The SNMM method is a semi-analytical solver having the properties of dimensionality reduction to reduce the computational costs; it is especially useful for microwave and optical integrated circuits where fabrication is often done in a layered structure. Furthermore, at some layer interfaces, very thin surfaces such as good conductor surfaces and metasurfaces can be deposited to achieve desired properties such as high absorbance and/or anomalous reflection/refraction. In this article, the 3-D SNMM method is further extended from a single interface to multiple layers so that the electromagnetic propagation and scattering in the longitudinal direction is treated analytically through reflection and transmission matrices by using the eigenmode expansions in the transverse directions. Therefore, it effectively reduces the original 3-D problem into a series of 2-D eigenvalue problems for periodic structures. We apply this method to characterize metasurfaces and lithography models and show that the SNMM method is especially efficient when the longitudinal layer thicknesses are large compared with wavelength. Numerical experiments indicate that the SNMM method is highly efficient and accurate for the metasurfaces and the lithography models.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Study of Diffuse Scattering in Massive MIMO Channels at Terahertz
    • Authors: Fawad Sheikh;Yuan Gao;Thomas Kaiser;
      Pages: 997 - 1008
      Abstract: The use of massive multiple-input multiple-output (MIMO) systems is becoming progressively feasible, as well as progressively important, as the carrier frequency increases. Terahertz (THz) frequencies lead to smaller-sized RF components including antennas, so that even antenna arrays with a large number of antennas have a reasonable form factor while providing large beamforming gain and multi-user MIMO (MU-MIMO) capability. However, the THz propagation mechanisms differ in various ways from previously explored channels. In fact, reflections by a rough surface and diffuse scattering mechanisms are the most critical features contributing to spatial and temporal dispersion at THz frequencies. For this article, first, we develop a hybrid modeling approach of 3-D ray-tracing simulations in a realistic office room at 300 and 350 GHz to obtain estimates of the impact of surface roughness on the channel capacity which depends on generic channel characteristics. Then, the indoor multipath propagation and its impact on massive MIMO channels considering smooth and rough surfaces are investigated by employing the Beckmann-Kirchhoff (B-K) model. Finally, channel capacities of indoor THz massive MIMO channels with different surface roughnesses for both line-of-sight (LoS) and non-LoS (NLoS) scenarios are calculated. Though based on modeling results, the scattering properties of materials can favorably be exploited to maximize spatial multiplexing gains, especially in LoS scenarios.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • 3-D Electromagnetic Scattering and Inverse Scattering by Magnetodielectric
           Objects With Arbitrary Anisotropy in Layered Uniaxial Media
    • Authors: Jiawen Li;Jianliang Zhuo;Zhen Guan;Feng Han;Qing Huo Liu;
      Pages: 1009 - 1022
      Abstract: 3-D electromagnetic (EM) scattering and inverse scattering of magnetodielectric objects with arbitrary anisotropy embedded in layered uniaxial media are studied. The stabilized biconjugate gradient fast Fourier transform (BCGS-FFT) method is employed to solve the forward scattering problem formulated by the combined field volume integral equation (CFVIE). In the inversion, we use the variational Born iterative method (VBIM) enhanced by the structural consistency constraint (SCC) to reconstruct eighteen unknown dielectric parameters of the scatterers simultaneously. In order to further improve the accuracy of the reconstructed permittivity, permeability, and conductivity of the scatterers, we propose the structural continuity scanning (SCS) technique. Comparisons between the BCGS-FFT solution and simulated results from finite element method (FEM) are performed to verify the reliability and accuracy of the forward solver. Meanwhile, we reconstruct the multiple anisotropic parameters of several typical structures embedded in layered uniaxial media to show the feasibility and anti-noise ability of the inversion algorithm.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Sufficient Conditions for Zero Backscattering by a Uniaxial
           Dielectric-Magnetic Scatterer Endowed With Magnetoelectric Gyrotropy
    • Authors: Hamad M. Alkhoori;Akhlesh Lakhtakia;James K. Breakall;Craig F. Bohren;
      Pages: 1023 - 1030
      Abstract: As vector wavefunctions are available to represent incident and scattered fields in an isotropic dielectric-magnetic medium endowed with magnetoelectric gyrotropy, a transition matrix can be conceptualized to relate the scattered field coefficients to the incident field coefficients for scattering by an arbitrary scatterer composed of a linear medium. The elements of the transition matrix must satisfy certain conditions for zero backscattering. For a scatterer composed of a uniaxial dielectric-magnetic medium endowed with magnetoelectric gyrotropy, the extended boundary condition method (EBCM) can be formulated to determine the transition matrix. The numerical results obtained thereby lead to the formulation of a sufficient set of three zero-backscattering conditions: (i) the scatterer is a body of revolution with the incident plane wave propagating along the axis of revolution; (ii) the impedances of both mediums are identical; and (iii) the magnetoelectric-gyrotropy vectors of both mediums are aligned along the axis of revolution, whether or not both magnetoelectric-gyrotropy vectors are co-parallel.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Generalized Parametric Prediction Model of the Mean Radiative Temperature
           for Microwave Slant Paths in All-Weather Condition
    • Authors: M. Biscarini;F. S. Marzano;
      Pages: 1031 - 1043
      Abstract: The mean radiative temperature (Tmr) is a key function controlling the sky noise temperature in microwave receiving systems. A generalized parametric prediction (GPP) model of Tmr for microwave slant paths in all-weather conditions is formulated and presented. The proposed GPP model is aimed at being multifrequency and surface-temperature scaled, valid for elevation angles from 5° to 90° and for frequencies ranging from 5 to 95 GHz within the three transmission windows delimited by the water vapor and the oxygen absorption peaks. The core of the GPP model is a parametrization driven by a physically based radiative transfer approach taking into account extinction, emission, and multiple scattering. The expression of Tmr is normalized to the surface temperature of the considered site. The GPP model is verified with measurements available from the multi-instrument Italian Satellite (ITALSAT) campaign in Spino d'Adda, Milan, Italy, in 1994-1997, obtaining a fractional mean error ranging from 0.045 to 0.068. A comparison of the GPP model with the current ITU-R model shows a reduction in the root mean square error up to about 20 and 30 K, depending on the considered frequency.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Mid- and Low-Latitude Ionospheric D Region Remote Sensing by Radio
    • Authors: Feng Han;Bingyang Liang;Jiawen Li;Feifan Liu;Gaopeng Lu;Qing Huo Liu;
      Pages: 1044 - 1054
      Abstract: Radio atmospherics (sferics for short) are electromagnetic (EM) pulses discharged by lightning return strokes and can be used for D region remote sensing. A frequency-domain full-wave (FDFW) numerical model is developed to simulate sferics propagation in earth ionosphere waveguide (EIWG). For a certain sampling frequency, EM fields of sferics are decomposed into a series of plane waves in the spectral domain via 2-D spatial Fourier transforms. The magnetized cold plasma medium of ionosphere is divided into several thin layers with the arbitrary anisotropic dielectric constant for each layer. The EM fields at the sferics receiver site are evaluated by recursively computing the reflection and transmission matrices in all layer boundaries for all the plane wave components and performing 2-D numerical integration in the spectral domain. The earth flattening technique is adopted and the horizontal wave vector of each plane wave component is directly modified in the spectral domain to compensate for earth curvature effects. Interactions between plane waves and the magnetized cold plasma of ionosphere are analyzed and discussed. Comparisons between the FDFW computation and finite-difference time-domain simulation as well as field measured sferics are implemented to verify the accuracy and reliability of the proposed new model.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Numerical and Experimental Study on Backscattering Doppler Characteristics
           From 2-D Nonlinear Sealike Surface at Low Grazing Angle
    • Authors: Yidong Hou;Biyang Wen;Caijun Wang;Yingwei Tian;
      Pages: 1055 - 1065
      Abstract: This article studies both experimentally and numerically the backscattering radar cross section (RCS) and Doppler spectrum characteristics from 2-D linear and nonlinear time-varying sea-like surface at UHF band under low grazing incidence. The small slope approximation and choppy wave model are applied to solve rough surface scattering and generate nonlinear sea waves, respectively. A coherent Doppler radar operating at 340 MHz was deployed at the tip of Huangqi peninsula in the southeast coast of China to measure the echo spectrum from the actual sea surfaces. At the same time, an ocean buoy was placed in the radar coverage to monitor the sea states. The RCS and Doppler spectrum are analyzed and compared comprehensively between radar measurements and numerical predictions. After compensating the influence of wind direction, the responses of radar echo power and numerical predicted RCS to wind speed are basically consistent and are more sensitive in low sea states. The correlation of Doppler spectra between radar measurements and numerical simulations exceed 0.96 during the whole experiment. The intensity of the high-order peaks increases rapidly with the wind speed, while the intensity of the Bragg peak decreases slightly. Doppler spectrum will be shifted by an amount proportional to radial surface current.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Doppler Characterization in Ultra Wideband BAN Channels During Breathing
    • Authors: Rubén-Gregorio García-Serna;Concepción García-Pardo;José-María Molina-García-Pardo;Leandro Juan-Llácer;Narcís Cardona;
      Pages: 1066 - 1073
      Abstract: Monitoring the physical parameters from devices inside the body, using ultra wideband (UWB) technology, enables the development of high bandwidth demanding applications in real time. The relative movement of the nodes deployed in the body, due to breathing, can give rise to a frequency shifting effect, increasing the fading level in the propagation channel during transmissions. In this article, therefore, we present a study of the frequency effects on the propagation channel derived from the relative movement between two nodes of a wireless body area network (WBAN), at least one of them placed inside the human body, caused by breathing. The study is performed on the basis of the Doppler spectrum characterization in terms of the shape fitting and frequency spread parameter derivation. Continuous wave (CW) signals have been used to cover the UWB range at four selected frequencies: 3.1, 4.8, 6, and 8.5 GHz, and a liquid phantom has been employed for emulating the dielectric properties of the high water content tissues at the considered UWB frequencies.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Characterization of Propagation Phenomena Relevant for 300 GHz Wireless
           Data Center Links
    • Authors: Chia-Lin Cheng;Alenka Zajić;
      Pages: 1074 - 1087
      Abstract: This article presents details about an extensive channel measurement campaign and subsequent statistical channel models for the characterization of 300 GHz channels for wireless rack-to-rack (R2R) and blade-to-blade (B2B) communications in a data center-like environment. Measurements were conducted in various scenarios such as R2R line-of-sight (LoS), R2R obstructed-LoS (OLoS), R2R reflected-non-LoS (RNLoS), R2R obstructed-RNLoS (ORNLoS), B2B RNLoS, B2B ORNLoS, and B2B LoS scenarios. In the aforementioned scenarios, we explored the impact of transmitter (Tx)/receiver (Rx) misalignment and obstructions such as cables, metal cabinets, and mesh structures on terahertz (THz) propagation, as well as feasibility of using existing metal objects as reflectors for NLoS links. For the R2R LoS scenario, an optical lens was used to extend the Tx-Rx separation distance. This led to a waveguide effect in the channels measured thereby resulting into a path loss exponent (PLE) of 1.48 with a shadowing gain of 0.7 dB. When obstructions of cables are present, ORNLoS link outperforms OLoS link with 2.5 dB lower shadowing gain and weaker multipath. Reflector in the RNLoS link has reflection coefficients very close to 1 for all incident angles. For the B2B scenario, a dual-reflector THz transceiver rack system is proposed to enable wireless links across vertically stacked servers and allow easy maintenance and repair of servers. The measured path loss closely follows the Friis values in the LoS link and in the RNLoS link with hollow vertical ground plane. When obstructions of cables are present, the ORNLoS link experiences 5-10 dB higher path loss and on average 0.25 GHz lower coherence bandwidth than the RNLoS link. The measured statistical channel properties show that the shadowing gain caused by cable clusters follows the log-normal distribution.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Plane Wave Scattering Dedicated Integral Equation
    • Authors: Benjamin Alzaix;Luc Giraud;Bastiaan L. Michielsen;Jean-René Poirier;
      Pages: 1088 - 1097
      Abstract: We present a variant of a boundary integral equation proposed by M. Herberthson in 2008-2010 for high-frequency plane wave scattering by perfectly conducting obstacles. This integral equation, as some of its predecessors, is entirely dedicated to a single direction of incidence. A significant reduction in the system size can then be obtained by looking for a pseudo-current, which is the actual surface current multiplied by the conjugate of the incident wave's phase function. This advantage is mostly lost when multiincidence problems have to be solved because, in addition to the source terms, the discretized operator must be recomputed for every new incidence. In this article, we make an explicit representation of the new operator as the sum of a conventional electric field integral equation (EFIE) which is independent of the direction of incidence, and an additional operator, which is dependent on the direction of incidence. The latter can be computed very efficiently such that a net performance gain is obtained with respect to the EFIE even for multiincidence problems.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Near-Field Wireless Power Transfer to Deep-Tissue Implants for Biomedical
    • Authors: Ke Zhang;Changrong Liu;Zhi Hao Jiang;Yudi Zhang;Xueguan Liu;Huiping Guo;Xinmi Yang;
      Pages: 1098 - 1106
      Abstract: Wireless power transfer (WPT) plays critical roles in powering deep-tissue implants, which also contributes to several emerging advances for biomedical engineering. To enable a high-power density region in implants, this article presents a method, termed the self-phasing technology, to focus electromagnetic fields from various paths at a deep-tissue spot. By performing the phase-conjugated operation on the incident signal and then retransfer back to the source, coherent RF power can be achieved without learning the precise or even dynamic locations of sources and concerning inhomogeneous medium perturbations. An external slot antenna array placed above skin surface 4 mm is considered as a transmitter and an implanted rectenna consisting of a magnetic resonant coil and an RF-to-dc rectifier circuit is treated as a receiver. The conversion efficiency of the rectifier circuit is optimized within the received power range and the measured efficiency of 50% can be achieved at 0 dBm. To visualize the transceiver effects of the integrated system under safety thresholds, a light-emitting diode (LED) is soldered at the terminal of the rectenna and measurements show that smooth drive can be achieved. Certain brightness of LED can demonstrate that the self-phasing technology can support WPT for biomedical applications.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Incorporating Spatial Priors in Microwave Imaging via Multiplicative
    • Authors: Nozhan Bayat;Puyan Mojabi;
      Pages: 1107 - 1118
      Abstract: This article presents a microwave imaging (MWI) algorithm that can incorporate prior structural information, also known as spatial priors (SP), about the object being imaged to enhance the achievable image quantitative accuracy. This algorithm: 1) is fully automated and 2) can work with both complete and partially available structural information. The core idea of this imaging algorithm is to use a multiplicative regularization term to incorporate SP, and a second regularization term to handle the lack of structural information in a given part of the imaging domain. This algorithm, which has been implemented for the 2-D transverse magnetic case, is evaluated against single-frequency and multiple-frequency synthetic and experimental MWI data sets.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Achieving Wider Bandwidth With Full-Wavelength Dipoles for 5G Base
    • Authors: Can Ding;Hai-Han Sun;He Zhu;Y. Jay Guo;
      Pages: 1119 - 1127
      Abstract: A new method of designing full-wavelength dipoles (FWDs) is presented. A dual-polarized antenna is built based on FWDs for base station applications as an example. The antenna has four FWDs arranged in a square loop array form. The employed FWDs are bent upward to maintain a small aperture size, so that the realized element still fits in traditional base station antenna (BSA) array. The antenna is first matched across the band from 1.63 to 3.71 GHz, which can cover both the LTE band from 1.7 to 2.7 GHz and the 5G (sub-6 GHz) band from 3.3 to 3.6 GHz simultaneously. Then, band-stop filters are inserted in the feed networks of the antenna to suppress the radiation between 2.7 to 3.3 GHz. The antenna is fabricated and tested. Experimental results validate the simulation results. Comparing with the previously available FWD that has a bandwidth of 32%, the FWD proposed in this article exhibits a much wider bandwidth of 78%. Moreover, this bandwidth is also comparable to and wider than those of the state-of-the-art BSAs based on half-wavelength dipoles (HWDs). The bandwidth enhancement and footprint reduction of the FWD in this article demonstrate a high potential of FWDs to be used in other applications.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Shared-Surface Dual-Band Antenna for 5G Applications
    • Authors: Teng Li;Zhi Ning Chen;
      Pages: 1128 - 1133
      Abstract: A shared-surface dual-band antenna is proposed for 5G operation using characteristic mode analysis (CMA). The surface is the integration of a metasurface at the S-band and a partially reflective surface (PRS) at the Ka-band. The resonant mode of the metasurface is excited by a microstrip-fed slot, and the PRS with a pair of substrateintegrated waveguide (SIW)-fed slots are employed to form a Fabry- Perot resonator antenna (FPRA). Measurements realized on a physical prototype of the antenna show a 10 dB impedance bandwidth of 23.45% and 9.76% and a realized gain that varies from 7.27 to 10.44 dBi and from 11.8 to 14.6 dBi, over the S-band (3.2-4.05 GHz) and the Ka-band (26.8-29.55 GHz), respectively.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Design of Compact, Single-Layered Substrate Integrated Waveguide Filtenna
           With Parasitic Patch
    • Authors: Kun-Zhi Hu;Ming-Chun Tang;Dajiang Li;Yang Wang;Mei Li;
      Pages: 1134 - 1139
      Abstract: A compact, single-layered substrate-integrated waveguide (SIW) filtenna with parasitic patch is synthesized and designed. A half-mode substrate-integrated rectangular cavity (HMSIRC) is adopted as the first stage resonator to reduce the circuit size. A parasitic patch functioning as the last stage resonator as well as the radiator is arranged closely to the HMSIRC so as to enhance the operational bandwidth and facilitate the filtering performance. Two broadside radiation nulls are realized at both the upper and lower band-edges to sharpen the band-edge roll-off rate: one is generated by the interaction between the HMSIRC and the parasitic patch, and the other is introduced by placing two pairs of shorting posts under the parasitic patch. The standard filter synthesis technology is utilized to guide the filtenna design. The optimized prototype was fabricated and measured. The measured results, in good agreement with simulated values, indicated the proposed filtenna provides a 5.1% fractional bandwidth, a maximum realized gain of 6.3 dBi, and a flat passband gain response along with excellent out-of-band selectivity, even with ultralow profile 0.015 λ0 and small volume 0.005 λ03.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Metamaterial-Loaded Compact High-Gain Dual-Band Circularly Polarized
           Implantable Antenna System for Multiple Biomedical Applications
    • Authors: Muhammad Zada;Izaz Ali Shah;Hyoungsuk Yoo;
      Pages: 1140 - 1144
      Abstract: This communication presents a metamaterial (MTM)-loaded compact dual-band circularly polarized antenna system suitable for multiple bio-telemetric applications. The proposed antenna system operates in the industrial, scientific, and medical (ISM) bands with center frequencies: 915 MHz (902-928 MHz) and 2450 MHz (2400-2480 MHz). The integration of an MTM structure with epsilon-very-large property on the superstrate layer of the antenna produces significant gain enhancement and strong circular polarization (CP) behavior at both the operating frequencies. The key features of the proposed antenna system are its compact size (7 mm × 6 × 0.254 mm), dual-band CP characteristics, significantly high gain values (-17.1 and -9.81 dBi in the lower and upper bands, respectively), and slot-less ground plane that reduces the complexity and backscatter radiation. The performance of the MTM-loaded antenna system is validated experimentally. The antenna is fabricated and integrated with dummy electronics and batteries and is enclosed in a 3-D printed device. The hermetically sealed device is tested in minced pork muscle to validate the simulation results. The measured impedance bandwidths of 35.8% and 17.8% are obtained in the lower and upper ISM bands, respectively. The specific absorption rate of the antenna system is evaluated at both frequencies in different tissues. Additionally, to determine the wireless communication range, the link margin is estimated at data rates of 100 kbps and 1 Mbps.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Wideband Circularly Polarized Substrate-Integrated Embedded Dielectric
           Resonator Antenna for Millimeter-Wave Applications
    • Authors: Mei-Di Yang;Yong-Mei Pan;Yu-Xiang Sun;Kwok-Wa Leung;
      Pages: 1145 - 1150
      Abstract: A singly fed wideband circularly polarized (CP) substrate-integrated dielectric resonator antenna (SIDRA) is proposed for millimeter-wave (mm-wave) applications. The SIDRA consists of an inner cylindrical dielectric resonator (DR), an outer ring DR, and a substrate-integrated waveguide (SIW) cavity. To generate CP fields, a cross-slot formed by two rectangular slots with different lengths is utilized to feed the DRA at its bottom. It has been found that owing to the embedded structure, the fundamental HEM11δ mode of the inner DR and the higher order HEM12δ+1 mode of the entire DR can be excited simultaneously, at adjacent frequencies. Moreover, owing to the different loading effects of the two feeding slots, the resonance frequencies of the nearly degenerate DR modes excited by the two slots are slightly different from each other. The two nearly degenerate modes lead to the wide impedance and axial ratio (AR) bandwidths of 34.6% and ~30%, respectively. In addition, due to the surrounding SIW cavity, the directivity of the antenna is greatly improved as compared with that of the isolated counterpart, with the maximum gain given by 8.15 dBic.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Compact Frequency-Reconfigurable Antenna With Independent Tuning for
           Hand-Held Wireless Devices
    • Authors: Sangeetha Subbaraj;Malathi Kanagasabai;M. Gulam Nabi Alsath;Sandeep Kumar Palaniswamy;Saffrine Kingsly;Indhumathi Kulandhaisamy;Arun Kumar Shrivastav;Rajesh Natarajan;Shanmugapriya Meiyalagan;
      Pages: 1151 - 1154
      Abstract: This communication presents the design of a compact loop antenna with independent frequency tuning. The proposed antenna consists of a feed line fed by a 50 Ω coaxial probe and four resonating arms on the adjacent sides of the feed line. The two outer resonating arms are directly coupled to the feed line and the other two inner resonating arms are coupled to the outer arms. The proposed antenna has a footprint of 25 mm × 10 mm × 0.2 mm. The designed antenna operates at 0.9, 2.4, 3.5, and 5.5 GHz. Each of these bands is individually tuned using varactor diodes. Thus, the aggregation of these tunable bands provides wide bandwidth. The impedance bandwidth and percentage bandwidth of the antenna are 270/1000/400/700 MHz and 33%/47.6%/11%/12.7%, respectively. Furthermore, the gain and efficiency of the antenna are 1.7/1.3/2.1/2 dBi and 60%/63%/65%/69%, respectively. The prototype antenna is fabricated and tested. The measured impedance and radiation characteristics of the antenna are in good correlation with the simulation results.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Wideband Resonant Cavity Antenna With Compact Partially Reflective
    • Authors: Fanji Meng;Satish K. Sharma;
      Pages: 1155 - 1160
      Abstract: A novel wideband resonant cavity antenna (RCA) with compact partially reflective surface (PRS) is presented, which is composed of a superstrate and a feed antenna. The superstrate is a dielectric slab with double-deck periodic array structure, where the superstratum is composed of square loop cells and substratum is composed of square loop aperture cells. This shows positive reflection coefficient phase, which in turn helps in obtaining wider RCA bandwidth. Contrary to the patch cell periodic array, a periodic array composed of square loop cells provides further compact structure. The feed system is a wideband aperture-coupled patch antenna, which is composed of square patch, ground plane with I-shaped slot, and fork-shaped feed network. This dual-arm feed network helps in obtaining the maximum gain at the center frequency. The superstrate with positive reflection coefficient phase provides the minimum gain at the resonant frequency. This in turn helps RCA in obtaining invariant gain in the operation band. Experimental verification was performed and the results show that this RCA offers fractional bandwidth of around 23.6% at X-band (8.88-11.25 GHz, S11 ≤ -10 dB) and gain (13.36-13.92 dBi) is almost invariant over the bandwidth. The measured patterns are symmetric with low cross-polarization levels.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • A Miniaturized Dual-Band Implantable Antenna System for Medical
    • Authors: Farooq Faisal;Muhammad Zada;Asma Ejaz;Yasar Amin;Sadiq Ullah;Hyoungsuk Yoo;
      Pages: 1161 - 1165
      Abstract: In this communication, a biotelemetry device for scalp implantation is proposed with an ultraminiaturized and simple-structured implantable antenna that exhibits dual-band characteristics in the industrial, scientific, and medical bands (915 MHz and 2.45 GHz). The proposed system incorporates two batteries and microelectronic components in a total volume of 434.72 mm3. The recommended antenna has a reduced volume of 9.8 mm3 (7 mm $times7$ mm $times0.2$ mm), which is the smallest antenna presented so far. In homogeneous and heterogeneous environments, the designed antenna system has peak gain values of −28.04 and −28.94 dBi, respectively, at 915 MHz, and −23.01 and −23.06 dBi, respectively, at 2.45 GHz. For validation, the prototype of the antenna and corresponding system are immersed in a 3-D head phantom (saline solution), and the measured results are found in close agreement with the simulation results. Additionally, the data communication range is analyzed through a link budget calculation at several data rates and an input power of −16 dBm. The radiation of the antenna system in the two principal planes (E and H) are similar to being omni-directional and directed away from the anatomical human body model as mandatory for the telemetry applications. Hence, the proposed antenna system can be employed in scalp implantation, especially for intracranial pressure monitoring.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Improved Model for Inclined Coupling Slots in the Feed of a Planar Slot
    • Authors: Jacob C. Coetzee;Soumya Sheel;
      Pages: 1166 - 1169
      Abstract: The conventional design equations for centered-inclined slots of a planar array feed network rely on certain assumptions regarding the phase relationship between the elements of the scattering parameters of coupling junctions, and do not account for higher-order coupling between tilted slots. Phase variations between S-parameters give rise to excitation errors in the radiating branches, and discounting the effects of higher-order coupling causes the input reflection coefficient minimum to deviate from the design frequency. In this communication, we derive new design relations which accommodate phase differences between individual scattering parameters and compensate for higher-order coupling. Compensation is achieved with the addition of closed-form terms in the expression for the equivalent impedance of the coupling slots. The effectiveness of the proposed procedure is demonstrated by means of an illustrative design example.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Pattern-Reconfigurable Planar Array Antenna Characterized by Digital
           Coding Method
    • Authors: Xin Ge Zhang;Wei Xiang Jiang;Han Wei Tian;Zheng Xing Wang;Qiang Wang;Tie Jun Cui;
      Pages: 1170 - 1175
      Abstract: We propose a low-profile and high-gain pattern-reconfigurable planar array antenna (PRPAA) based on digital coding characterization. The radiating elements in the PRPAA are designed ingeniously to realize digital “0” and “1” elements. By dynamically encoding the digital radiating elements with different coding patterns, various radiation beams can be achieved and switched in real time based on one antenna aperture. More importantly, for different coding patterns, the number and direction of the radiation beams of the digital PRPAA can be well predicted. We fabricate such a PRPAA and validate its digital-controllable radiation patterns experimentally. This communication provides many opportunities to realize low-cost, lightweight, high-gain, and multi-unit PRPAA, which offers promising applications in massive multi-in multi-out (MIMO) antenna array system, smart antenna, radar system, and dynamic microwave imaging.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Metrics for Localized Beams and Pulses
    • Authors: Walter Fuscaldo;Santi C. Pavone;
      Pages: 1176 - 1180
      Abstract: Geometric and energy metrics are here proposed to gauge the confinement properties of localized electromagnetic beams (e.g., Bessel beams) and pulses (e.g., X-waves) in both the nondispersive and dispersive cases. As is well known, the frequency superposition of Bessel beams sharing the same axicon angle leads to the generation of tightly bounded wavepackets, namely X-waves, with remarkable spatio-temporal confinement properties. In the nondispersive case, the axicon angle does not change with frequency, and these features can be predicted by closed-form expressions. Remarkably, it is found that the volumetric confinement of such pulses can be optimized for a specific axicon angle. Since the geometric metrics do not account for the unavoidable presence of energy tails outside the main spot, energy metrics are here introduced and compared with the purely geometric definition. Finally, the dispersive case is investigated, accounting for the typical wavenumber dispersion of radial waveguides. As a result, the axicon angle changes with the frequency, and fundamental limits exist for the maximum theoretical fractional bandwidth. Interestingly, design criteria based on approximate analytical expressions are derived to optimize the confinement, even in the dispersive case.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • An Analytical Solution of Electromagnetic Radiation of a Vertical Dipole
           Over a Layered Half-Space
    • Authors: Mohsen Eslami Nazari;Weimin Huang;
      Pages: 1181 - 1185
      Abstract: An analytical solution for the wave scattering generated by a vertical dipole above horizontally stratified media is proposed. The solution to the problem is given in terms of 2-D Fourier transforms, which leads to Sommerfeld-type integrals. The solution is decomposed into three terms and an analytical closed-form solution as a function of physical layers specification for the electric field intensity is deduced from the results. Two terms are expressed with hyperbolic functions and the third term is presented using the Gauss error function. A numerical evaluation of the integrals that constitute the formal result of the problem validates the accuracy and efficiency of the proposed solution at various frequencies as well as at different distances from the source. The presented solution is also implemented for the particular case of surface ocean scattering in the high frequency (HF) band and the overall behavior of the solution, which consists of three terms, is evaluated by their distance from the antenna in the near field and far-field regions.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Wideband and Wide-Angle Single-Layered-Substrate Linear-to-Circular
           Polarization Metasurface Converter
    • Authors: Hong Bin Wang;Yu Jian Cheng;Zhi Ning Chen;
      Pages: 1186 - 1191
      Abstract: A wideband and wide-angle linear-to-circular polarization converter (LCPC) based on a single-layer dielectric substrate is proposed. The converter element consists of a metal strip cross backed by a strip horizontally and centrically located on the other metallic layer. The vertical arm of the strip across the whole surface performs as a highpass filter with a wide passband above a low cutoff frequency. Meanwhile, the horizontal strip resonates at a high out-of-band frequency and also offers a wideband response below the resonant frequency. Another two short strips vertically and horizontally placed around the crosses increase the phase shift caused by the crosses and improve both the passbands. Using equivalent circuit models and ANSOFT HFSS, an example of LCPC is designed with the overall element size of only 0.11λ0 × 0.21λ0 for a 90° phase difference and wide-angle stability over the wide operation band. The prototype shows the simulated / measured axial ratios (ARs) below 3 dB over the bandwidth of 69%/74% for a normal incidence wave and 54% for the oblique incident angle of 55° in yz plane, respectively. With the insertion loss of less than 3 and 2 dB, the measured 3 dB AR bandwidth keeps 70% and 55%, respectively.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Frequency-Selective Structures With Suppressed Reflection Through Passive
           Phase Cancellation
    • Authors: Yuping Shang;Xue Lei;Cheng Liao;Jianlin Chen;
      Pages: 1192 - 1197
      Abstract: Multilayered frequency-selective structures with checkerboard arrangement are presented to demonstrate the application of passive phase cancellation to reduce the strong reflection from a traditional 2-D single-layer slot-type frequency-selective surface (FSS). The simple square slot is used as the basic unit to construct the involved supercells which are further combined to achieve the multilayered structures. The properly selected spacing between layers is mainly responsible for producing supercells with out-of-phase reflections, which establishes the destructive interference of reflected waves. In comparison with the traditional FSS, a band of reflection reduction is observed below the passband through the principle of phase cancellation. Meanwhile, the multilayered structures can maintain a passband with small insertion loss for transmission. The effect of increased supercell types on the bandwidth enhancement of reflection reduction and that of checkerboard arrangement on the angular performance are considered. A good agreement between simulation and measurement validates the observations.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • An Optimized One-Step Leapfrog HIE-FDTD Method With the Artificial
           Anisotropy Parameters
    • Authors: Yong-Dan Kong;Chu-Bin Zhang;Qing-Xin Chu;
      Pages: 1198 - 1203
      Abstract: By introducing the artificial anisotropy (AA) parameters, a 3-D one-step leapfrog hybrid implicit-explicit finite-difference time domain (HIE-FDTD) method is proposed, which can reduce the numerical dispersion error without increasing the computational cost. The formulation of the AA one-step leapfrog HIE-FDTD method is obtained by introducing the relative permittivity and permeability tensors in the original one-step leapfrog HIE-FDTD method. The Courant-Friedrichs-Lewy (CFL) stability condition of the AA one-step leapfrog HIE-FDTD method is close to that of the original one-step leapfrog HIE-FDTD method. In addition, the proposed HIE-FDTD method has lower numerical dispersion error and higher calculation accuracy than that of the one-step leapfrog HIE-FDTD method. Finally, to testify the characteristics of the proposed HIE-FDTD method, numerical simulation experiments are given.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • 2-D Coherence Factor for Sidelobe and Ghost Suppressions in Radar Imaging
    • Authors: Shiyong Li;Moeness Amin;Qiang An;Guoqiang Zhao;Houjun Sun;
      Pages: 1204 - 1209
      Abstract: The coherence factor (CF) is defined as the ratio of coherent power to incoherent power received by the radar aperture. The incoherent power is computed by the multi-antenna receiver based only on the spatial variable. In this respect, it is a 1-D CF, and thereby the image sidelobes in down-range cannot be effectively suppressed. We propose a 2-D CF by supplementing the 1-D CF by an incoherent sum dealing with the frequency dimension. In essence, we employ both spatial diversity and frequency diversity which, respectively, enhance imaging quality in cross-range and range. Simulations and experimental results are provided to demonstrate the performance advantages of the proposed approach.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Corrections to “An Effective-Current Approach for Hallén’s Equation
           in Center-Fed Dipole Antennas With Finite Conductivity” [Jun 19
    • Authors: Themistoklis K. Mavrogordatos;Anastasios Papathanasopoulos;George Fikioris;
      Pages: 1210 - 1210
      Abstract: Provides corrections to errors in the original paper. Corrected equations (17) and (18) are presented here.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Comments on “Frequency Diverse Array Antenna Using Time-Modulated
           Optimized Frequency Offset to Obtain Time-Invariant Spatial Fine Focusing
    • Authors: M. Fartookzadeh;
      Pages: 1211 - 1212
      Abstract: In the recent articles [1]–[4], including the abovementioned article, time-modulated frequency diverse arrays (FDAs) have been presented to obtain time-invariant spatial patterns. The presented FDAs in [1]–[3] have the feature of time-invariant spatial focusing, which means they have a constant maximum in a time duration T at a point with desired range r and angle $theta $ . In [4], the pattern is time invariant, yet not focused. However, in this communication, it is indicated that the patterns are obtained using the incorrect definition of time in some equations. The equation system of [3] is explained here, which can be extended to [1], [2], and [4], explicitly.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Reply to Comments on “Frequency Diverse Array Antenna Using
           Time-Modulated Optimized Frequency Offset to Obtain Time-Invariant Spatial
           Fine Focusing Beampattern”
    • Authors: Wen Wu;Da-Gang Fang;
      Pages: 1213 - 1213
      Abstract: We thank Fartookzadch [1] for reading our article [2] and giving positive comments on the optimized method in [2] to be interesting and useful, especially for the comments on the time-invariant issue, which give us the opportunity to correct some results and to discuss some considerations on time-invariant focusing beampattern that actually we borrowed from [3].
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Comments on “Wideband Radiation Reconfigurable Microstrip Patch Antenna
           Loaded With Two Inverted U-Slots”
    • Authors: Seyed-Ali Malakooti;Christophe Fumeaux;
      Pages: 1214 - 1215
      Abstract: This comment investigates some missing fundamental simulation and measurement results affecting the practical performance of the antenna presented in [1]. In order to properly demonstrate the practical consequences of these omissions, we provide simulation results as well as experimental validation using a prototype with the exact dimensions as in [1], fed with an ultrawideband coupler [2], as shown in Fig. 1. Radavaram and Pour [1] have claimed 68% fractional bandwidth for a multiport antenna based only on a single-port input reflection coefficient (S11). Unfortunately, the mutual coupling between the antenna ports (S21) is not shown in their article. We have performed corresponding simulations using Ansys HFSS and found that the missing coupling coefficient between the elements within the band of interest has a magnitude close to 0 dB, which is validated by the experimental results, as illustrated in Fig. 2(a). This suggests that the proposed design is operating as a wideband bandpass filter in lieu of a radiating element. The clear misunderstanding in the scattering performance arises from the fact that for dual-port antennas fed by in-phase and out-of-phase inputs, the active scattering parameters are of fundamental importance. Active scattering parameters for dual-port devices are defined as the combinations of S11 and S21 (some references, such as [4] and [5], use differential and common mode scattering parameters or Sdd and Scc). They determine the overall scatte-ing performance when a feeding network is connected to a multiport antenna. For instance, [3] (see [1, Ref. 20]), [4], and [5] are aimed at reducing Sdd11 to below −10 dB for the differential S-parameter. They use the correct definition of Sdd11, as given in the following [3, eq. (8)]:
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Reply to Comments on “Wideband Radiation Reconfigurable Microstrip Patch
           Antenna Loaded With Two Inverted U-Slots”
    • Authors: Sai Radavaram;Maria Pour;
      Pages: 1216 - 1218
      Abstract: We appreciate the comments given in [1] on active scattering parameters and realized gain of the antenna in [2]. In this correspondence, we would like to address the aforementioned parameters, which were simply overlooked in [2], by slightly modifying the antenna structure in [2]. The resultant antenna is now capable of radiating both the broadside and conical patterns over a 45% active impedance bandwidth, which is still much greater than that of the microstrip patch antennas with reconfigurable radiation patterns reported in [3]–[13]. The modifications to [2] to improve the isolation between the two ports include incorporating an H-shaped stub, inspired by the one in [14], at the center of the patch, as shown in Fig. 1(a), and placing shorting vias at appropriate positions on the antenna, which extends from the top layer of the patch to the ground plane. These vias, along with the narrow slits at the center of the patch, considerably aided in reducing the mutual coupling between the probes. The H-shaped stub and the shorting vias on it facilitated in improving the impedance matching. In the interest of maximizing the overall active reflection coefficients of both the modes of operation, i.e., SUM and DIFFERENCE modes, L-shaped probes are used to excite the antenna stru-ture in lieu of the SMA probes. To integrate the L-probes, the profile of the antenna is now increased from $sim 0.02lambda _{mathrm {d}}$ to $sim 0.08lambda _{mathrm {d}}$ , where $lambda _{mathrm {d}}$ is the dielectric wavelength at the center frequency of operation.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Comments on “Broadband Symmetrical E-Shaped Patch Antenna With Multimode
           Resonance for 5G Millimeter-Wave Applications”
    • Authors: Wonpyo Kwon;Junho Park;Wonbin Hong;
      Pages: 1219 - 1219
      Abstract: In [1], it was stated “As shown in Fig. 3(a), near the longitudinal slot, the electric field is zero in the direction of the z-axis, and the resonance frequency f1 of the TM10 mode can be derived as (1), where c represents the speed of light in a vacuum, $varepsilon _{e}$ represents the effective dielectric constant, $Delta l$ represents the extending length due to the effect of the fringing field [2], W represents the patch width, $W = 2w_{2} + 2w_{3} + w_{4}$ , as shown in Fig. 1, and $Delta w$ represents the length when the electric field is zero in the direction of the z-axis, as shown in Fig. 3(a)”
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
  • Reply to Comments on “Broadband Symmetrical E-Shaped Patch Antenna With
           Multimode Resonance for 5G Millimeter-Wave Applications”
    • Authors: Jiexi Yin;Qi Wu;Chen Yu;Haiming Wang;Wei Hong;
      Pages: 1220 - 1220
      Abstract: We acknowledge the anonymous reader’s comments on the above article [1]. We have carefully checked the equations in [2] as well as the corresponding computer code. Equation (1) in [2] is incorrect, as kindly pointed out in the above-mentioned comments. It should be corrected as (2) in the comments. However, in our computer code, we used the correct equation. Thus, parameters f1 and W in [2] are both correct.
      PubDate: Feb. 2020
      Issue No: Vol. 68, No. 2 (2020)
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