Recent Articles
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Radiation of an Antenna Enclosed by a Spherical Radome Made of an Orthorhombic Dielectric-Magnetic Medium
21 August 2024 Hamad M. Alkhoori and Mousa Hussein treated the radiation of a structure comprising a spherical radome enclosing an antenna and made of an orthorhombic dielectric-magnetic medium semi analytically in this paper. Inside the radome, the radiation field phasors due to the antenna and reflected field phasors due to the radome are expanded into vector spherical wave functions of the radome’s medium. This yields two sets of unknown expansion coefficients: the radiation-field expansion coefficients, and the reflected-field expansion coefficients. The radiation-field expansion coefficients are obtained in terms of the current distribution in the antenna upon using the bilinear-form dyadic Green functions of the radome’s medium.
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Optimizing Isolation in Interleaved Co-Frequency Orthogonally Polarized Circular Patch Array Antennas Using Conformal Mantle Cloaks and Integrated Decoupling Patches
19 August 2024 Reza Masoumi, Robab Kazemi and Aly E. Fathy present two interleaved, tightly spaced circular patch array antennas that operate at the same frequency but with orthogonal polarizations. The arrays are arranged in the E-plane, with one array rotated 90 degrees to achieve orthogonal polarization—Array-I is x-polarized, while Array-II is y-polarized. This configuration provides both spatial and polarization diversity, which helps reduce signal degradation caused by multipath fading and enhances overall channel capacity. They also investigate the effectiveness of conformal mantle cloaks and decoupling patches in isolating two interleaved co-frequency circular patch array antennas.
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A Low Distortion Radiation Pattern Ultra-Wideband TEM Horn Antenna
02 August 2024 Mahdi Zoghi, Farrokh Hodjatkashani and Mir Emad Lajevardi introduce a low distortion radiation pattern ultra-wideband (UWB) transverse electromagnetic (TEM) horn antenna designed to operate in the 2 to 18 GHz frequency range. The modification is achieved using a non-uniform antenna feed without changing the antenna’s flare structure. The main-lobe radiation pattern of the antenna at higher frequencies eliminates ripples by using a non-uniform feeding technique compared to conventional TEM horn antennas, in which this issue exists. The measurement results pursue simulation results with a good agreement.
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3-D Chipless RFID Tag for Anti-Counterfeiting Applications
02 August 2024Suvadeep Choudhury, Filippo Costa, Giuliano Manara and Simone Genovesi propose and investigate a novel methodology for designing Chipless Radio Frequency Identification (RFID) tags realized using the Additive Manufacturing technologies and exhibiting a high number of identification states. An encoding scheme based on the resonances and anti-resonances of the input impedance of the resonator is employed for identifying the tag, which is achieved by exploiting the set of zero-crossing points of the tag reactance. A tolerance analysis is also performed to avoid any ambiguity in the reading process and to minimize the redundancy, thus providing unique electromagnetic signatures which are also suitable for anti-counterfeiting applications. Several prototypes have been fabricated and tested to assess the practical implementation of the proposed encoding scheme.
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A Study of Wideband Dielectric Resonator Antennas Loaded With Special Dispersive Materials
01 August 2024 Xiantao Yang, Elliot Leon Bennett, Ilkan Calisir, Qiang Hua, Jianliang Xiao and Yi Huang present a comprehensive study of wideband dielectric resonator antennas (DRAs) loaded with special dispersive materials. The concept and theory for a new class of wideband and compact DRAs are introduced for the first time using the new material whose relative permittivity is inversely proportional to the frequency power of n (i.e., εr (f)=k / fn , k is a constant). Traditional DRAs are normally of limited bandwidth and unstable radiation patterns. The proposed new DRAs exhibit excellent advantages in bandwidth enhancement, size reduction, single-mode purity (predominantly supporting a single mode with minimal interference from other unwanted modes), and stable radiation patterns.
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Beam Steering for Time Modulated Arrays
23 July 2024 Gonzalo Maldonado, Abdoalbaset Abohmra, Alberto Reyna, Luz. I. Balderas, Marco A. Panduro and Jesús Cruz Garza propose an analytical method to calculate the switch-on sequences that provides Time Modulated Antenna Arrays (TMAA) with beam scanning in the sideband region. Such time sequences can be calculated to locate the main beam both in the azimuth and elevation planes. A comparison between H. Shanks’ method and the method proposed in this paper is presented. The radiation patterns of uniform linear, square and circular arrays are presented to demonstrate the efficacy of the proposed method.
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Electromagnetic Scattering Properties of Metal Powder Cloud for Laser Powder Bed Fusion (LPBF) Additive Manufacturing (AM)
22 July 2024 Farzaneh Ahmadi, Jiming Song and Reza Zoughi investigate the potential for employing a well-established electromagnetic (EM) model to monitor the scattering properties of spatters. This approach serves as a potential tool to identify variations in spattering behavior that might be associated with defect generation during the process. The study explores how parameters, such as spatial distribution and the number of particles (in a given volume), impact the scattering properties, accuracy, and efficiency of the method. Changes in spattering spatial distribution resulting from variations in processing parameters, including laser power, scan speed, and chamber pressure, were investigated.
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A Low-RCS, High-Gain and Polarization-Insensitive FP Antenna Combing Frequency Selective Rasorber and Metasurface
11 July 2024 Shaojie Wang, He-Xiu Xu, Mingzhao Wang and Shiwei Tang present a novel method to engineer high-gain and polarization-insensitive Fabry-Perot (FP) antenna with low scattering by combining a polarization-insensitive broadband frequency selective rasorber with partially reflective surface (FSRP) and a reflective metasurface. The FSRP element consists of an upper indium tin oxide layer printed on polyethylene glycol terephthalate substrate, a metallic loop, and a metallic patch in the middle and bottom layer, respectively, which is designed to absorb most of out-of-band incidence while achieving in-band reflection. The bottom metallic patch is a partially reflected surface which is utilized to construct an FP resonant cavity with the reflective metasurface to ensure in-band radiation.
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Design an Omnidirectional Circularly-Polarized Antenna for Azimuth Wide-Angle Scanning Array
11 July 2024 Xin Guan, Yijing He, Zhenghui Xue, Wu Ren and Weiming Li propose an omnidirectional circularly-polarized antenna. Specifically, a thin and compact open cavity loaded with a capacitive impedance surface is used to provide the horizontally-polarized electrical-field component. While the verticallypolarized electrical-field component is achieved by a thin open cavity placed above the metal ground with a small gap. Connecting the two radiating cavities with a metal plate, the omnidirectional circularlypolarized antenna can be constructed using one simple feed. Outstanding azimuth gain variation of less than 1 dB and axial ratio less than 3 dB are obtained for the proposed antenna. Owing to the proposed antenna has omnidirectional characteristics, it can be applied to a wide-angle scanning array.
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Low-Profile ESPAR Using Metamaterial-Inspired Structure
10 July 2024 Amir Jafargholi, Mahmood Safaei, Romain Fleury and Rahim Tafazolli addresses the 3D nature of traditional Electronically Steerable Parasitic Array Radiators (ESPARs). Additionally, the required distance between the main radiator and the parasitic elements usually affects the antenna’s electrical size and the frequency bandwidth. To overcome these issues, the cylindrical parasitic elements in conventional ESPARs are replaced with Metamaterial-inspired structures that mimic artificial magnetic conductors (AMC). The AMC is realized by a capacitively loaded loop (CLL). PIN diodes electrically control the CLL’s behavior while radially loading a printed loop antenna. Switching ON/OFF the diodes changes the direction of the main lobe, resulting in a compact, single-layer, low-profile, and cost-effective structure.