Perfect Conductor Research Articles

Surface Susceptibilities as Characteristic Models of Reflective Metasurfaces

While metasurfaces (MSs) are constructed from deeply subwavelength unit cells, they are generally electrically large and full-wave simulations of the complete structure are computationally expensive. Thus, to reduce this high computational cost, nonuniform MSs can be modeled as zero-thickness boundaries, with sheets of electric and magnetic polarizations related to the fields by surface susceptibilities and the generalized sheet transition conditions (GSTCs). While these two-sided boundary conditions (BCs) have been extensively studied for single sheets of resonant particles, it has not been shown if they can correctly model structures where the two sides are electrically isolated, such as a fully reflective surface. In particular, we consider in this work whether the fields scattered from a fully reflective MS can be correctly predicted for arbitrary field illuminations, with the source placed on either side of the surface. In the process, we also show the mapping of a perfect electric conductor (PEC) sheet with a dielectric cover layer to bianisoptropic susceptibilities. Finally, we demonstrate the use of the susceptibilities as compact models for use in various simulation techniques, with an illustrative example of a parabolic reflector, for which the scattered fields are correctly computed using an integral-equation (IE)-based solver.

On the Use of Reconfigurable Space-Time Metasurface Enclosures for Microwave Imaging

The use of space-time metasurfaces as microwave imaging (MWI) system enclosures (casings) is discussed. In contrast to commonly used MWI enclosures, these can be reconfigured so as to implement different boundary conditions for data collection and processing schemes. In particular, the use of a space-time-modulated metasurface enclosure to implement two seemingly contradictory boundary conditions for MWI, namely, open space and perfect electric conductor conditions, are discussed along with quantitative imaging results.

On the Casimir effect from the zero-point energy: a tangential force and its properties

We investigate the Casimir effect in the systems that consist of parallel but misaligned finite-size plates from the point of view of zero-point energy. We elaborate that the zero-point energies of the radiation field in the perfect conductor systems would generate a tangential Casimir force, and explore the properties and consequences of this tangential force in various conductor systems. Thereafter, we generalize our discussion to dielectrics. After calculating the total zero-point energies of the surface modes in the multilayered systems, we show that the tangential force also exists in dielectrics. We obtain the finite-conductivity corrections to the tangential force for imperfectly conducting plates, and calculate the finite-temperature corrections to the force. The typical strength of the tangential force suggests it might be observable.

Applying a Set of Orthogonal Basis Functions in Numerical Solution of Hallen's Integral Equation for Dipole Antenna of Perfectly Conducting Material

The focus of this paper is on solving Hallen's integral equation for a diploe antenna of perfectly conducting material. A special representation of orthogonal triangular basis functions is used to implement an effective numerical method for solving this equation. The Hallen's formulation is treated in detail and illustrative computations are given for current distributions and radiation patterns.

Global solutions to an initial boundary problem for the compressible 3D MHD equations with Navier-slip and perfectly conducting boundary conditions in exterior domains

An initial boundary value problem for compressible magnetohydrodynamics (MHD) is considered on an exterior domain (with the vanishing first Betti number) in in this paper. The global existence of smooth solutions near a given constant state for compressible MHD with the boundary conditions of Navier-slip for the velocity filed and perfect conduction for the magnetic field is established. Moreover the explicit decay rate is given. In particular, the results obtained in this paper also imply the global existence of classical solutions for the full compressible Navier–Stokes equations with Navier-slip boundary conditions on exterior domains in three dimensions, which was not available in literature prior to the work in this paper, to the best of knowledge of the authors’.

Inorganic-polymer hydrogel electrolyte enabling aqueous Zn-ions batteries

Zinc-ion batteries with gel polymer electrolytes (GPE) have attracted great attention owing to their characters of safe, high performance, and environmental friendly. However, their practical application is limited by low ion conductivity and poor mechanical strength. In this work, a perfect composite GPE were obtained by introducing graphene oxide into SA and PAAM double-networks. The GPE was endowed with a perfect ionic conductivity of 12.12 mS cm−1. After 500 charge/discharge cycles at a rate of 1 C, the Zn-SAG-LiFePO4 battery showed a discharge specific capacity retention of 63.3 % and a Coulomb efficiency about 100 %. The hydrogel electrolyte is considered to enable the practical applications of Zinc-ion batteries.

Broadband millimeter-wave metasurface antenna array with printed ridge gap waveguide for high front-to-back ratio

A novel broadband metasurface (MTS) antenna array with high front-to-back ratio (FBR) is proposed for 28 GHz millimeter-wave applications. With slot pairs loaded on patch cells, an aperture-coupled slotted-mushroom MTS antenna is designed to obtain broadband radiation characteristics with a compact size. To suppress the backward radiation of this antenna, the printed ridge gap waveguide (PRGW) technology with a perfect magnetic conductor (PMC) shielding made of mushroom unit-cells underneath the microstrip feeding line is applied. On this basis, a 4 × 4 MTS antenna array with the PRGW feed network is developed. Simulated results show that the FBR can be highly improved by over 16 dB within the entire bandwidth. To validate the design, a prototype of the proposed antenna is fabricated. Measured results show that an FBR greater than 28 dB can be obtained over a 24% impedance bandwidth (from 24.9 GHz to 31.7 GHz) with the reflection coefficient less than −10 dB. The measured antenna gain ranges from 17 dBi to 19.2 dBi and the corresponding measured aperture efficiencies are 35% and 45.6%. The measured results also suggest that the proposed MTS antenna possesses −35 dB cross-polarization level and stable radiation patterns. In addition, the proposed antenna remains a very low profile of 1.7 mm (0.17λ0 at 28 GHz). All the achieved features indicate that the proposed MTS antenna is an important candidate for B5G and 6G wireless communication.

ONDAS DE ALFVÉN DE GRAN AMPLITUD EN PLASMAS PARCIALMENTE IONIZADOS

In this paper it is analyzed the propagation of large amplitude Alfvén waves in partially ionized plasmas (PIP) when electronic pressure, Hall and ambipolar terms of Ohm’s law are taken into account. Instead of linearizing and developing the perturbation in monochromatic waves, it is proposed that the perturbation satisfy the Alfvén wave’s conditions. As a result, a solution is found that in the fully ionized limit, it coincides with Sallago and Platzeck solution for Alfvénwaves in Hall magnetohydrodynamics (doi:10.1029/2003JA009920 ). Furthermore, if electronic pressure and Hall terms are null, in the linearized limit, the damping is equal to the one described by De Pontieu, B. Martens, P. C. H. and Hudson, H. S. (DOI = 10.1086/322408), if one imposes that the plasma is a perfect conductor.

Topological current divider in a Chern insulator junction

A Chern insulator is a two-dimensional material that hosts chiral edge states produced by the combination of topology with time reversal symmetry breaking. Such edge states are perfect one-dimensional conductors, which may exist not only on sample edges, but on any boundary between two materials with distinct topological invariants (or Chern numbers). Engineering of such interfaces is highly desirable due to emerging opportunities of using topological edge states for energy-efficient information transmission. Here, we report a chiral edge-current divider based on Chern insulator junctions formed within the layered topological magnet MnBi2Te4. We find that in a device containing a boundary between regions of different thickness, topological domains with different Chern numbers can coexist. At the domain boundary, a Chern insulator junction forms, where we identify a chiral edge mode along the junction interface. We use this to construct topological circuits in which the chiral edge current can be split, rerouted, or switched off by controlling the Chern numbers of the individual domains. Our results demonstrate MnBi2Te4 as an emerging platform for topological circuits design.

Rapid Numerical Analysis of Electrically Large PEC Platforms With Local Variations via a Platform Green’s Function Method

The aim of this article is to perform a rapid electromagnetic (EM) analysis of large perfectly electric conducting (PEC) platforms with local variations. Such problems often require many-query simulations to navigate complex parameter spaces and thus quickly become computationally expensive. The proposed work starts with a stationary-variable domain decomposition, where the computational domain is decomposed into large fixed parts and small portions with local variations. Subsequently, we introduce a separable and compressible platform Green’s function at the outer surface of those variable subdomains in an upfront offline calculation. Once obtained, the online computational complexity does not depend on the size of the in situ platform. With the validation of numerical results, we conclude that the proposed work has the potential to greatly speed up the online evaluation of local designs and optimizations compared to the brute-force computation.

A Fast Converging Resonance-Free Global Multi-Trace Method for Scattering by Partially Coated Composite Structures

Global and local multitrace formulations (MTFs) provide a flexible and efficient method for the modeling of scattering and transmission of time harmonic electromagnetic (EM) waves by composite structures. This contribution extends the domain of applicability of global MTFs to cases where penetrable domains, perfectly conducting domain, and perfectly conducting thin sheets are all part of the design. A novel and easy to implement resonance-free equation to model scattering by perfect conductors is introduced. A Calderón preconditioner designed to limit the number of iterations required for the solution of the discrete system is designed and studied. The accuracy, flexibility, and efficiency of the method are demonstrated on a representative range of examples.

Modeling and Minimization of the Parasitic Capacitances of Single-Layer Toroidal Inductors

High-frequency power converters need electromagnetic interferences filters using common and differential mode chokes with low parasitic capacitance to comply with the electromagnetic compatibility standards. This article proposes a modeling method of this capacitance and ways to minimize it. The studied components are ring core inductors with magnetic materials considered as perfect conductors or with high permittivity, such as nanocrystalline material and most Mn-Zn ferrite materials. In comparison to other work in the literature, the proposed approach takes into account the curvature of the turn, in addition to the coating of the core and the insulation layer of the wire. The hypotheses, used in this article to simplify the real geometry, are compatible with two-dimensional (2-D) approaches to compute the parasitic interturns and turn–core capacitances. These capacitances are evaluated thanks to the 2-D finite element method. The obtained model allows accurate evaluation of the effect of turn–core space on the parasitic capacitance, and enables to reduce its value with a limited impact on the volume of the magnetic component.

Design of a Quasi-TEM Waveguide for the High-Intensity-Field Measurement of the Field-Induced Metasurfaces

Field-induced metasurface is an applicable technique to prevent the high-intensity-radiated-field (HIRF). To improve the measurement accuracy, this article presents the design of a waveguide that forms high-intensity TEM waves within its closed transverse boundaries. The proposed quasi-TEM waveguide adopts two artificial magnetic conductors (AMCs) on the sidewalls of a standard rectangular waveguide. And the construction of the AMC is based on the theory of high impedance surface (HIS), which performs perfect magnetic conductor (PMC) properties at its resonant frequency. Then, a prototype is designed and fabricated to measure the electric field distributions and demonstrate the theoretical analysis and simulation. The measurement results indicate that the proposed waveguide could realize a 1 dB rippled electric-field distribution in more than 90% region, compared to that of 30% in the standard waveguide. Finally, high-intensity-field measurements of a field-induced sample, energy selective surface (ESS), are compared in the proposed waveguide and a standard waveguide. The comparison result has proved that the proposed waveguide could better evaluate the HIRF performance of the field-induced metasurface.

Reconfigurable graphene-based metamaterial polarization converter for terahertz applications

This study proposes a high-gain polarization converter using a graphene-based metamaterial array, a rectangular array comprising 20 periodic unit-cell elements. Each graphene-based metamaterial unit-cell element contains a rectangular patch with four triangular-shaped graphene parts at its four corners placed over a rectangular substrate backed with a perfect electric conductor and has a relative permittivity of εsub = 3.38. The metamaterial characteristics of the proposed graphene-based metamaterial unit-cell element are obtained over frequencies of 1.5–2.2 terahertz (THz). The graphene-based metamaterial array is placed over a linearly polarized slot antenna operating at 1.8 THz, with a maximum gain of 5.5 dBi. The linearly polarized wave radiated from the slot antenna can be converted into reconfigurable right-handed or left-handed circular polarizations according to the graphene parts’ biasing states. Moreover, the slot antenna’s operating − 10 dB bandwidth (BW) is increased by 22.2%, and the gain is enhanced to 8 dBi at the same operating frequency. A reconfigurable polarization conversion for the slot antenna can be obtained over a wide 3 dB axial ratio BW from 1.75 to 1.92 THz (20%–3 dB BW).

All-angle reflectionless negative refraction with ideal photonic Weyl metamaterials

Negative refraction, an unnatural optical phenomenon in which the incident and the refracted waves reside on the same side of the surface normal, has been demonstrated with the invention of negative index media based on artificially engineered photonic structures called metamaterials. It has received wide attention due to its potential applications in imaging, nonlinear optics, and electromagnetic cloaking. However, it is highly challenging to realize negative refraction operating at all angles and with the perfect transmission. In this work, leveraging the recent development in topological photonics, we propose to realize reflectionless negative refraction for all incident angles with a topological metamaterial. The proposed metamaterial possesses two Weyl points of opposite topological charges. By interfacing the metamaterial with a perfect electric conductor (PEC) or a perfect magnetic conductor (PMC), the Fermi arc connecting the two Weyl points can take the form of a half-circle possessing a positive or a negative refractive index. Importantly, due to the topological protection, there is no reflection at the interface between the PEC and PMC covered areas, leading to the observation of all-angle negative refraction without reflection at the boundary. Our work provides a new platform for manipulating the propagation of surface waves, which may find applications in the construction of integrated photonic devices.

Asymptotic analysis for non-local problems in composites with different imperfect contact conditions

We consider a composite material made up of a hosting medium containing an ε-periodic array of perfect thermal conductors. Comparing with the previous contributions in the literature, in the present paper, the inclusions are completely disconnected and form two families with dissimilar physical behaviour. More specifically, the imperfect contact between the hosting medium and the inclusions obeys two different laws, according to the two different types of inclusions. The contact conditions involve the small parameter ε and two positive constants . We investigate the homogenization limit and the limits for going to 0 or , taken in any order, with the aim to find out the cases in which the two limits commute.

Building a surrogate model of a perfect electric conductor using polynomial chaos expansion and the characteristic mode analysis

A surrogate model for a perfect electric conductor plate is built by using the polynomial chaos expansion method. The plate is excited via four capacitive coupling elements for which the locations are determined by the analysis of the current distribution for each mode provided by the characteristic mode analysis. A numerical model based on the method of moments is then created to generate a database needed to build the surrogate model. Radiation patterns calculated by the surrogate model are compared with those given by the numerical model. The results show that the surrogate model can mimic the numerical model and it can be used to replace complex numerical models to save computation time and to alleviate the burden on the computation resources. Then, a sensitivity analysis is conducted to exhibit the effect of the parameter deviations on the overall antenna performance and to reveal the influential input parameters. The results of sensitivity analysis are used to reduce the complexity of the overall structure.

Simulation of the interaction of light with 3‐D metallic nanostructures using a proper orthogonal decomposition‐Galerkin reduced‐order discontinuous Galerkin time‐domain method

AbstractIn this artice, we report on a reduced‐order model (ROM) based on the proper orthogonal decomposition (POD) technique for the system of 3‐D time‐domain Maxwell's equations coupled to a Drude dispersion model, which is employed to describe the interaction of light with nanometer scale metallic structures. By using the singular value decomposition (SVD) method, the POD basis vectors are extracted offline from the snapshots produced by a high order discontinuous Galerkin time‐domain (DGTD) solver. With a Galerkin projection and a second order leap‐frog (LF2) time discretization, a discrete ROM is constructed. The stability condition of the ROM is then analyzed. In particular, when the boundary is a perfect electric conductor condition, the global energy of the ROM is bounded, which is consistent with the characteristics of global energy in the DGTD method. It is shown that the ROM based on Galerkin projection can maintain the stability characteristics of the original high dimensional model. Numerical experiments are presented to verify the accuracy, demonstrate the capabilities of the POD‐based ROM and assess its efficiency for 3‐D nanophotonic problems.

TM Scattering by a Shallow Elliptical-Shaped Cavity

In this letter, the problem of electromagnetic scattering by a shallow elliptical-shaped cavity in a perfect electric conductor plane is considered. We propose an efficient modal approach based on the region-matching technique that can calculate scattered fields without the use of the Mathieu functions. By enforcing boundary conditions at a semicircular auxiliary border, a system of linear equations is constructed. The results obtained by this method are compared with those provided by the method of moment. Finally, the effect of the shape of the cavity on the scattering signature is investigated.

Comparative analysis of dielectric substrate materials (FR-4 & RT/Duriod 5880) for antenna array (8*1) designing

In this communication a comparative study of two materials for designing antenna array (8*1) system, simulated by CST Microwave Studio for 5G mobile (base station) applications, is carried out. Array is constructed by FR-4 (low cost substrate material) and Rogers RT/ Duriod 5880 (high efficiency substrate material).Ground and conductor patch are made by PEC (perfect electric conductor).Comparison of design parameters has been done and results of simulated arrays for two materials are determined. A Wilkinson power divider network also has been designed by PEC material for feeding. Simulated array gain 10.31dBi for FR4 (8*1) substrate material and 15.59 dBi for Roger substrate in 5G range (3.4–3.6 GHz) mobile base station applications. Efficiency of Rogers substrate is 98.14% for 8*1 array. An antenna array (4*1) is fabricated over a double sided copper laminated FR-4 epoxy glass material and the result of S 11 is verified by vector network analyzer (VNA).