Recent Articles
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Transparent Graphene-Based RIS for 6G Communications in the THz Spectrum
29 October 2024 I. Marasco, C. Cantore, G. V. Bianco, G. Bruno, A. D'Orazio and G. Magno present a numerical investigation and the optimized design of a transparent graphene-based RIS operating in the THz spectrum. The aim of the paper is twofold: the former is to demonstrate the reconfigurability of the proposed RIS by exploiting two methods, referred to as “digital” and “analogical”. The latter is to demonstrate the effects of the losses and of the mutual coupling among unit cells on the power flow pattern. This aspect is crucial in the design of the RIS and cannot be overlooked, differently from other papers reported in the literature which analyze the RIS as an “ideal” structure evaluating only an analytical estimation of the array factor and neglecting the interaction among the unit cells.
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An Efficient Curvature-Based Synthesis Methodology for Rotationally Symmetric Shaped Reflector Antennas
25 October 2024 Manushanker Balasubramanian and Douglas H. Werner extend and apply a previously proposed B-spline curvature-based synthesis technique to the design of rotationally symmetric reflector antennas with shaped beam patterns. The approach is based on representing a reflector as a single curve that can be modified to alter the reflector’s shape. The curvature is evaluated and represented using B-spline polynomials. First, the control points of the spline curve are defined as variables and then a new curvature profile is generated. Following this step, the corresponding curve is synthesized using the proposed iterative algorithm. This process of optimizing the curvature using B-spline polynomials offers the ability to better control the shape of a reflector with very few design variables.
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Wireless Multi-Coil Transmission With a Rotating Part of the Internal Winding
24 October 2024Josef Pokorny, Premysl Dohnal and Petr Marcon discusse the basic principles of concentrating the radiated near non-radiant magnetic field by changing the angle of the winding sector of the spiral coils designed on a substrate for a standard PCB (printed circuit board). The relevant principles include: 1) Changing the shape and design of the movable inner part of the coil winding; together with the static part, the moving item can form a concentrated magnetic field in space, thus creating a magnetic vector. 2) The 2×2 matrix of these coils comprises individual resonators changing the shape of the magnetic field according to the shape, distance, and position of the receiver.
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H-Matrix Accelerated Direct Matrix Solver for Maxwell’s Equations Using the Chebyshev-Based Nyström Boundary Integral Equation Method
24 October 2024 Jin Hu, Emrah Sever, Omid Babazadeh, Ian Jeffrey, Vladimir Okhmatovski and Constantine Sideris formulate, test, and profile an H-matrix accelerated direct solver employing the high-order Chebyshev-based Boundary Integral Equation (CBIE) method for performance on high contrast dielectric materials and electrically large perfect electric conductor objects. The matrix fill performance of the CBIE proves to be fast for small to moderately sized problems compared to its counterparts, e.g., the locally corrected Nyström (LCN) method, due to the way it handles the singularities by means of a global change of variable method.
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A mmWave Transmitting Time Modulated Array Using Bespoke GaAs Integrated Circuits—Prototype Design and Laboratory Trials at 73 GHz
16 October 2024 Edward A. Ball and Sumin David Joseph present a prototype design and testing of an E band mmWave Time Modulated Array (TMA). The PCB based array has a 3 dB RF bandwidth of 71-73 GHz and a peak gain of −2 dBi on the first harmonic steered beam. The TMA second harmonic beam gain is within 0.9 dB of a conventional phase-shifter based array, in a like-for-like theoretical comparison. An array gain of +11.5 dBi is predicted for a full on-chip implementation. Good agreement between theoretical and prototype measured gains and array patterns are reported. Beam steering and phase correction are implemented using an FPGA, requiring only 2 digital lines per array element.
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Beam Shaping of a Dual-Reflector Antenna Using a Reflectarray as Subreflector and Embedded Unit Cell Patterns
09 October 2024 Marzieh Mehri Dehnavi and Jean-Jacques Laurin propose a phase-only synthesis technique for shaping the beam of a circularly polarized dual-reflector antenna with a subreflector consisting of a reflectarray and a main parabolic reflector. The proposed technique exploits the element patterns of each reflectarray unit cell embedded in the whole system, including a feed horn, a reflectarray, and a main reflector. By using a penalty function that forces only the fitting of the desired and obtained patterns, the algorithm leads to a quasi-random phase distribution on the reflectarray and a poor radiation pattern. A term for minimizing the Laplacian of the phase distribution is added to the penalty function to force a smoothly varying phase distribution on the reflectarray.
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Transparent Low-Profile and Wideband ITO-Glass Microwave Absorber
07 October 2024 Ahmed Hosameldin Khadrawy and Ahmed Abdelmottaleb Omar propose a transparent wideband microwave absorber by integrating Indium Tin Oxide (ITO) with glass in order to achieve both high microwave absorption and optical transparency. The design is constructed from three layers of glass substrate with etched ITO with different sheet resistance on each layer. The absorber features a combination of high dielectric constant material to accomplish the low-profile design and matching layer to achieve wide absorption bandwidth. The absorber demonstrates 115.64% fractional bandwidth from 3.48 GHz to 13.02 GHz with a structure thickness of 0.077 λmin , where λmin is the free-space wavelength at the lowest operating frequency.
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A Hybrid Frequency Selective Absorber With Dual-Polarized Wireless Communication and Ultra-Wideband Absorption
30 September 2024 Youquan Wen, Sai-Wai Wong, Chunlin Ji, Ruopeng Liu and Yejun He propose a circuit design of decoupling between frequency selective absorbers layer and antenna layer. The hybrid FSA with antenna circuit achieves in-band wideband dual-polarized transmitting/receiving and ultra-wideband absorption of both in-band and out-of-band. The two circuit layers operate independently, resolving the problems of inter-layer interference of conventional multi-layer FSA with antenna circuit. Additionally, the antenna configuration allows for excitation at the receiving end, providing broadband radiation capability without affecting in-band absorption.
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X-Band Waveguide Reflectionless Filtering Antenna Array With High Selectivity
30 September 2024 Jun Ma, Fuchang Chen and Kairan Xiang propose a waveguide reflectionless filtering antenna array with high selectivity. Instead of reflecting the out-of-band signal back to the source, the proposed antenna array dissipates the energy through a lossy network, which can reduce the interference to the former stage. The prototype circuit of the reflectionless filtering antenna array based on the complementary duplex theory is established, consisting of a bandpass network and a bandstop network, whose responses are completely complementary. High selectivity is achieved by introducing non-resonating nodes (NRNs) and configuring the transmission zeros (TZs) of the bandpass network and the reflection zeros (RZs) of the bandstop network to be set at the same frequency.
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Multibeam Antennas Based on 3-D Discrete Lenses With Magnified Field-of-View
27 September 2024 Lisa Berretti, Renaud Loison, Esteban Menargues, Lucas Polo-López, Giovanni Toso and María García-Vigueras introduce and numerically analyze a new type of beamforming network (BFN) based on three-dimensional (3D) discrete lenses as an antenna system capable of generating multiple beams within a large Field-of-View (FoV). To enhance scanning capabilities, these lenses have their back part and associated feed array magnified relative to the front part. It is also shown that the radiating elements constituting the front part of the lens, due to the shape of their element factor, tend to limit the pointing direction of the overall antenna pattern, but their influence decreases as the lens dimension. Accordingly, a large front array is chosen to scan wide angles and mitigate this limitation.
