各向异性介质涂覆PEC平板的反射场分析

利用射线级数法分析各向异性介质涂覆PEC平板反射场。该分析引入Chew使用的状态向量来表征场,利用传输矩阵表征各向异性涂覆层中的电磁波经过了一次下行路径和上行路径之后幅值和相位产生的变化。将涂覆层表面总场表示成一个射线级数。每项级数分别判定成入射场、单次反射场及n次反射场,并通过涂覆层顶层和底层表面上的边界条件进行约束。从实际应用的角度考虑,对n次反射场之和的贡献选取截断次数,并验证了截断次数选取的合理性。文中的算例和分析说明了射线级数法的有效性及所得反射场的合理性。     

Resonant frequency of a rectangular microstrip patch on severaluniaxial substrates

A full-wave analysis for determining the resonant frequency of a rectangular microstrip patch on multiple uniaxial anisotropic layers with or without an anisotropic overlay is presented. Two independent methods are used to derive the immittance matrix for the patch, from which the resonant frequency is determined. They are the Hertz vector potentials and the modified spectral domain immittance approach. Numerical results of the resonant frequency are given for several patch configurations, including cases of a patch on a single anisotropic layer, a patch on a double layer with one layer anisotropic and one layer isotropic, a suspended patch resonator with anisotropic substrate, a patch with anisotropic overlay and a patch on two anisotropic substrates with an anisotropic overlay. Changes in the resonant frequency of up to 58% are reported as n_x/n _y is changed from 1.0 (for isotropic substrates) to 2.0     

一种用于双各向异性材料参数反演的新模型

针对双各向异性材料参数的反演,在多频点测量、多厚度测量、多入射角测量模型的基础上,本文首次提出了一种用于双各向异性材料参数反演的新模型,该模型是由同材料前后两层相对旋转一定角度的双层组成。利用一阶状态矢量法,推导得到了该模型反射传输的计算公式,并分析了双层同材料测量模型的传输特性。与单层平板模型传输特性进行比较表明:有的传输参数在单层时对媒质参数敏感,而有的在双层时对媒质参数敏感。本文的工作为双各向异性吸波材料参数的反演打下了基础。     

金属衬底多层各向异性介质电波反射特性研究

通过分析和计算多层各向异性介质的电磁波传输矩阵,导出了金属衬底上多层各向异性介质的电磁波反射系数计算方法,举例验证了该计算方法的正确性.作为一个应用例子,初步分析了金属衬底上各向异性材料的极化转换特性,为复杂电磁材料的电磁散射近似计算提供了理论基础.     

Edge-based FEM solution of scattering from inhomogeneous andanisotropic objects

This paper presents an application of the edge-based vector finite element method to scattering problems of anisotropic and inhomogeneous objects. Based on conventional FEM functional, a hybrid finite element-surface integral formulation is established by introducing permittivity and permeability tensors. The space domain is divided into interior and exterior regions by an imaginary surface conformal to the scatterer. Edge vector finite elements are used to model the anisotropic and inhomogeneous interior, and a surface integral equation is used to model the unbounded exterior. Compared to other hybrid techniques, the approach here retains the symmetry and sparsity of the FEM matrix and introduces only one type of unknown equivalent current in the moment matrix equation. To validate the theory, typical 2-D numerical results are first presented, which show excellent agreement with exact eigenmode expansion solutions or accurate MoM data     

A comparison of anisotropic PML to Berenger's PML and itsapplication to the finite-element method for EM scattering

The use of an anisotropic material for the boundary truncation of the finite-element method is considered. The anisotropic material properties can be chosen such that a plane-wave incident from free space into the anisotropic halfspace has no reflection. Because there is no reflection, the material is referred to as a perfectly matched layer (PML). The relationship between the anisotropic PML and the original PML proposed by Berenger (see J. Comp. Phys., vol.114, p.185-200, October 1994) is considered. The anisotropic PML is applied to the finite-element solution of electromagnetic (EM) scattering from three-dimensional (3-D) objects. Numerical results are presented to demonstrate the accuracy of the PML     

Rectangular patch resonator with laminated ground plane

In this paper, we analyze the effect of a laminated ground plane on the resonance frequency of rectangular patch resonators. We model each lamina of the ground plane as an anisotropic layer and use a transition matrix to relate the tangential field components in different laminae. An integral equation is formulated in the spectral domain, and Galerkin's method is applied to solve the integral equation for the resonance frequencies of the patch resonator. A perturbation approach is also derived for comparison. The effects of substrate dielectric are studied. The resonance frequency variation thus obtained will be useful in designing patch resonators attached to composite laminated surfaces     

多向定向铁纤维吸波材料的雷达反射特性研究

基于电磁场理论用传输矩阵方法数值计算具有金属基底多向定向铁纤维吸波材料的雷达反射特性.结果表明具有强各向异性的单定向铁纤维材料,通过多向定向铺层在铺层层数不是很小时(通常大于10层)该吸波材料表面的反射场近似各向同性特性;指出它的反射特性可用反射系数平行分量(R//)0表征;通过等效电磁参数的计算和实验验证了数值分析的正确性.     

Propagation Characteristics of a Microstrip Line Printed on a General Anisotropic Substrate

An analysis is presented for determining the propagation modes in a microstrip line printed on a substrate having both electric- and magnetic-type general anisotropies. An integral equation is derived for the unknown current distribution on the microstrip line. The kernel of this equation is a complicated 2x2 matrix function of the substrate anisotropy and of the substrate thickness. In order to determine the dispersion relations for the propagating waves, this integral equation is reduced into a finite system of linear equations by employing Galerkin's technique. Numerical results are given for several cases, and the effect of rotating the anisotropy axis in anisotropic substrates is investigated. The proposed method can be employed to compute the propagation characteristics of microstrip lines printed on anisotropic substrates.     

Finite element beam propagation method for anisotropic opticalwaveguides

A finite element beam propagation method (BPM) for anisotropic optical waveguides is newly formulated. In order to treat a wide-angle beam propagation, a Pade approximant operator is employed and to avoid nonphysical reflection from computational window edges, a transparent boundary condition is extended to anisotropic materials. To show the validity and usefulness of this approach, the numerical results for an anisotropic planar waveguide and a magnetooptic channel waveguide are presented     

Network Representation and Transverse Resonance for Layered Anisotropic Dielectric Waveguides

First, the matrix wave impedance in an unbounded uniaxial lossless dielectric material is determined. Next, the transformation properties of the input impedance of a terminated anisotropic layer are established. It is then demonstrated that the boundary conditions in an anisotropic dielectric slab waveguide lead to a generalized transverse resonance condition involving the previously obtained matrix input impedances. Network equivalent representations are given for waveguides fabricated with dielectrics in polar and longitudinal orientations. The results show that a circuit approach to the analysis and design of planar anisotropic dielectric waveguides is feasible and practicable.     

Radiation from a dipole near a general anisotropic layer

The radiation properties of a dipole source located near a gyrotropic layer are investigated analytically. Both electric and magnetic anisotropy of the most general form are assumed. Fourier-transform domain field representations in conjunction with matrix analysis techniques are used to facilitate the analysis. Transmission phenomena through the general anisotropic layer are investigated by examining the radiation patterns at the far-field region. The analysis is also used to derive the response of the anisotropic layer to an incident plane wave. In this case, the transmission and reflection coefficient matrices are obtained     

Electromagnetic scattering by stratified inhomogeneous anisotropic media

An analytical formulation is presented for the computation of scattering and transmission by general anisotropic stratified material. This method employs a first-order state-vector differential equation representation of Maxwell's equations whose solution is given in terms of a4 times 4transition matrix relating the tangential field components at the input and output planes of the anisotropic region. The complete diffraction problem is solved by combining impedance boundary conditions at these interfaces with the transition matrix relationship. A numerical algorithm is described which solves the state-vector equation using finite differences. The validation of the resultant computer program is discussed along with example calculations.     

Integral equation based analysis of scattering from 3-D inhomogeneous anisotropic bodies

This paper presents an integral equation based scheme to analyze scattering from inhomogeneous bodies with anisotropic electromagnetic properties. Both the permittivity and permeability are assumed to be generalized tensors. Requisite integral equations are derived using volume equivalence theorem with the electric and magnetic flux densities being the unknown quantities. Matrix equations are derived by discretizing these unknowns using three dimensional Rao-Wilton-Glisson basis functions. Reduction of the integral equation to a corresponding matrix equation is considerably more involved due to the presence of anisotropy and the use of vector basis function; methods for evaluation of the integrals involved in the construction of this matrix is elucidated in detail. The method of moments technique is augmented with the fast multipole method and a compression scheme. The latter two enable large scale analysis. Finally, several numerical results are presented and compared against analytical solutions to validate the proposed scheme. An appendix provides analytical derivations for the formulae that are used to validate numerical method, and the necessary formulae that extends the approach presented herein to the analysis of scattering bianisotropic bodies.     

广义柱形坐标系各向异性完善匹配吸收媒质

Ｂｅｒｅｎｇｅｒ提出的完善匹配层只能用于直角坐标系。本文将完善匹配各向异性吸收媒质推广到广义柱形坐标系。推导是在广义柱形坐标系均匀媒质的Ｍａｘｗｅｌｌ方程与直角坐标系各向异性媒质的Ｍａｘｗｅｌｌ方程之间等效基础上进行的。得出了广义柱形坐标系完善匹配层电导率计算公式。     

截断各向异性介质的修正NPML吸收边界条件

基于各向异性介质中的时域有限差分（Finite-Difference Time-Domain,FDTD）方法及近似完全匹配层（Nearly Perfect Match Layer,NPML）原理,提出一种截断各向异性介质的修正的NPML吸收边界条件.通过对Maxwell旋度方程中的空间偏导数进行坐标拉伸并结合空间插值方法,推导出易于在FDTD方法中实现的吸收边界公式.计算了电偶极子辐射场的反射误差,验证了这种吸收边界截断二维各向异性介质的有效性.三维算例中数值模拟了时谐场的相位分布,以及不同网格NPML吸收层随时间变化的反射误差.数值结果表明NPML吸收边界能有效吸收各向异性介质中的电磁波.     

Simulation of a periodic dielectric corrugation with an equivalent anisotropic layer

A periodic, corrugated, dielectric layer is simulated by an anisotropic dielectric layer of equal thickness. The tensor elements of the equivalent dielectric layer are given in terms of the permittivity of the dielectric material, the period of the surface corrugation, and the width of the corrugations. The validity of this technique is verified by comparing the reflection coefficient of the equivalent layer with that of the corresponding corrugated layer using the moment method. Employing a multiple layer approach, the technique is extended to handle periodic surfaces with arbitrary cross sections which can be used to design millimeter wave dielectric plate polarizers and absorbers.     

ELECTROMAGNETIC WAVE PROPAGATION IN MAGNETIC MULTILAYERS-NON-RECIPROCAL REFLECTIONS''''

A theory of EM wave propagation through magnetic multilayers and superlattices is presented based on the propagation matrix of a magnetic film. By using the P matrix, the transmission and reflection coefficients of layered magnetic media, including: (l)semi-infinite magnetic surfaces, (2) magnetic multilayers, (3) semi-infinite magnetic superlattices are obtained. The numerical results show that the EM modes of a magnetic layer system is excited and manifested as the sharp dips in the S-polarized reflection and the dispersion curves of the magnetic polaritons can be measured by a method similar to the attenuated total reflection (ATR) technique.     

Full vectorial finite element formalism for lossy anisotropicwaveguides

An efficient computer-aided solution procedure based on the finite-element method is developed for solving general waveguiding structures containing lossy, anisotropic materials. In this procedure a formulation in terms of the transverse magnetic field component is adopted and the eigenvalue of the final matrix equation corresponds to the propagation constant itself. Thus one avoids the unnecessary iterations which arise when using complex frequencies. To demonstrate the strength of the presented method, numerical results are shown for a rectangular waveguide filled with lossy anisotropic dielectric with off-diagonal elements in a permittivity tensor and compared with those obtained by the telegrapher equation method. The results are in excellent agreement both for phase and for attenuation     

Analysis of multilayered periodic structures using generalizedscattering matrix theory

The use of generalized scattering matrix theory is proposed as a fast, efficient approach for analyzing multilayer structures where in each layer is either a diffraction grating or a uniform dielectric slab, and all grating layers have the same periodicity. The overall scattering from the structure is determined by first evaluating a matrix of scattering parameters for each individual layer and then forming a scattering matrix for the entire structure by a procedure analogous to the cascading of networks in circuit theory. Higher-order spatial (Floquet) harmonics, including nonpropagating modes and cross-polarized fields, are taken into account as necessary. The approach is illustrated by computing the reflection coefficient of a multilayered resistive strip grating as a function of frequency