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Ultrathin Microwave Devices for Polarization-Dependent Wavefront Shaping Based on an Anisotropic Metasurface
摘要： Metasurfaces have recently become a promising material, offering new degrees of freedom in molding electromagnetic wave properties. In this work, we propose and numerically investigate ultrathin microwave devices for polarization-dependent wavefront shaping based on an anisotropic metasurface, which consists of a square metal ring with a cross, a dielectric substrate, and a metal ground plane. It is demonstrated the proposed metasurface can independently manipulate reflective x- and y-polarized wavefronts at frequency of 15 GHz via engineering of the metal cross. Furthermore, the reflective efficient is extremely high, reaching a near-unity value of 0.98. Based on this anisotropic metasurface, a polarization beam splitter is achieved by artificially arranging the spatial distribution of metasurfaces with prescribed geometries. In addition, we successfully design a focusing metasurface to separate the x- and y-polarized beams via focusing them at different positions. The proposed approach paves a way toward the applications of the metasurface in a microwave band.
关键词： electromagnetic metamaterials,microwave propagation,beam steering,microwave antennas
更新于2025-09-23 15:22:29
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A flexible procedure to avoid the boundary materials singularities in 2D transformation-based cloaks
摘要： An out-of-plane coordinate transformation can avoid singular materials in a two-dimensional electromagnetic cloak. Based on numerical simulations of elliptical cylinders, in this paper we show that the use of two different constants to define the out-of-plane stretching can result in anisotropic materials with lower values and yet with a better scattering reduction for a given incident wave direction.
关键词： scattering cross-width,Cloaking,coordinate transformation,electromagnetic metamaterials
更新于2025-09-23 15:21:21
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The Application of Least-Squares Finite Element Method to Simulate Wave Propagation in Bianisotropic Media
摘要： The finite element method (FEM) has been one of the major numerical techniques for electromagnetics (EM) ever since the introduction of the spurious-free edge element. On the other hand, a so-called least-squares finite element method (LSFEM) is becoming increasingly popular due to its unique properties. For instance, the generated stiffness matrix is positive definite. Effort has been made to apply this node-element-based LSFEM to model EM problems, mostly in the theoretical aspect. In this paper, we will use normalized Maxwell’s equations incorporated with the constitutive relations of bianisotropic media, which represents the most general cases in the linear regime. Subsequently, the corresponding variational formulation is derived, followed by the generation of matrix systems. We then implement and validate various boundary conditions. Further we apply this scheme to simulate wave scattering in the presence of bianisotropic media that are categorized into 3 types. A good convergence rate and agreement between the LSFEM results and the referenced solutions has been achieved, which proves the Lagrange-element-based LSFEM as a feasible alternative to the edge-element-based FEM currently used in EM modeling.
关键词： Electromagnetic metamaterials,Electromagnetic propagation,Finite element analysis
更新于2025-09-19 17:15:36
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Fast Analysis of Metasurfaces through Temporal Coupled-mode Theory
摘要： In this article, a rigorous temporal coupled-mode theory (CMT) formalism is developed, to analyze metasurface (MTS)-based structures. Such MTSs are generally rather complex, requiring extensive, full-wave simulations. To facilitate their design and minimize the associated computational demand, the CMT solves a small linear system of equations, fed by the results of certain much simpler and less time- and memory-consuming eigenvalue problems. The proposed method is versatile and offers an initial, valuable estimation of the structure’s frequency response, which may be used as a guideline for the ?nal MTS ?ne tuning. As proof of concept, split-ring resonator (SRR) MTSs coupled to microstrip lines are analyzed, and their response is compared with the full-wave ?nite-element method (FEM) results.
关键词： Coupled-mode analysis,planar arrays,metasurfaces (MTSs),electromagnetic metamaterials
更新于2025-09-16 10:30:52
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Metamaterial-Inspired Vacuum Electron Devices and Accelerators
摘要： Metamaterials (MTMs) are structured materials with subwavelength features that can be engineered to have some unique properties not found in nature, such as negative refractive index, reversed Doppler effect, and reversed Cherenkov radiation. Based on these novel MTMs, several important research groups have made great attempts to develop novel MTM-inspired vacuum electron devices (VEDs) and accelerators. Just as solid-state power devices are innovated by incessant emerging of new semiconductor materials, VEDs can also be inspired by MTMs to have very remarkable advantages, such as smaller size, higher power, higher efficiency, and/or larger gain relative to conventional VEDs, such as traveling-wave tubes, backward-wave oscillators, and klystrons. Similarly, relative to conventional accelerators, MTM-inspired accelerators have obvious advantages, such as smaller size and higher accelerating gradient. Furthermore, MTM-inspired devices have promising applications in areas such as radar, communication, electronic warfare, microwave heating, and imaging.
关键词： high-power microwaves,oscillators,vacuum electron devices (VEDs),electromagnetic metamaterials (MTMs),amplifiers,Accelerators
更新于2025-09-09 09:28:46
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Characterization of additively manufactured cellular alumina dielectric structures
摘要： Additive manufacturing (AM, also known as 3D printing) can produce novel three-dimensional structures using low-loss dielectric materials. This enables the construction of dielectrics with complex shapes that enable innovative microwave applications such as resonators, filters, and metamaterial lenses. This paper addresses the production and characterization of cellular structures of various designed densities created with a low loss ceramic material, alumina (aluminum oxide), via vat photopolymerization. The permittivity of these printed structures is variable over roughly an octave, with a range of relative permittivites from 1.78 to 3.60, controlled via part geometry.
关键词： electromagnetic metamaterials,dielectric materials,ceramics,printing,design for manufacture
更新于2025-09-09 09:28:46