Electromagnetic scattering by a wedge with anisotropic impedancefaces

Electromagnetic scattering from the edge of an anisotropic impedance wedge, illuminated at oblique incidence, is addressed. In particular, the paper provides a review of existing solutions for this important topic in diffraction theory. Both numerical and analytical techniques, suitable to properly account for the scattering properties of the wedge's anisotropic impedance faces, are considered     

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.     

Electromagnetic scattering by an inhomogeneous plasma anisotropic sphere of multilayers

Electromagnetic scattering by an inhomogeneous plasma anisotropic sphere is formulated and obtained, where the inhomogeneous plasma anisotropic sphere is divided into (s-1) homogeneous anisotropic spherical layers. The electromagnetic fields in the inner spherical multilayers and outer free space of the inhomogeneous plasma anisotropic spherical structure can be expanded in terms of the spherical vector wave functions in plasma anisotropic medium and in isotropic medium, respectively. By applying the continuous boundary conditions of electromagnetic fields on the spherical interfaces of the (s-1)-layered homogeneous anisotropic plasma medium, the unknown expansion coefficients of fields in the multilayered plasma spherical structure are obtained, and then the electromagnetic field distributions are calculated. Numerical results for the very general inhomogeneous plasma dielectric material sphere are given and the data in a special case are obtained using the present method and the method of moments accelerated with the conjugate-gradient fast-Fourier-transform approach and compared to each other to verify the correctness and applicability of the present analysis.     

Numerical analysis of the diffraction at an anisotropic impedancewedge

A numerical approach to the electromagnetic scattering of a plane wave impinging at skew incidence on the edge of a wedge with two different anisotropic face impedances is presented. The diffracted field is obtained by applying the finite-difference (FD) method to solve two coupled parabolic equations. The solution obtained is valid in the high-frequency region     

Electromagnetic scattering by anisotropic impedance half and fullplanes illuminated at oblique incidence

The three-dimensional electromagnetic (EM) scattering from half and full plane configurations, both characterized by a perfectly conducting and an anisotropic impedance face, is analyzed. The anisotropic impedance boundary condition considered for the loaded face is suitable for modeling corrugated surfaces or strip-loaded grounded dielectric slabs used to realize artificially hard or soft surfaces, with a tensor surface impedance exhibiting a vanishing impedance along the corrugations or strips and a diverging impedance in the orthogonal direction. Previous rigorous solutions, valid when the vanishing impedance direction is either parallel or perpendicular to the edge, are generalized here to the case in which the direction of vanishing impedance is arbitrarily oriented     

Electromagnetic scattering from anisotropic plasma-coated perfect electromagnetic conductor cylinders

The scattering of electromagnetic waves by a perfect electromagnetic conductor (PEMC) cylinder coated with a homogeneous plasma anisotropic material is studied in this paper. Both of the transverse electric and the transverse magnetic polarizations of the incident waves have been analyzed and formulated. The presented analysis and formulations are general for any perfect conductor cylinder (PEC, PMC, or PEMC) with general isotropic/anisotropic material coatings that include plasma and metamaterials. The co-polarized and the cross-polarized components of the scattered fields are computed for different cases of the anisotropic plasma coated PEMC cylinders and for an anisotropic plasma column. Bistatic echo widths for the cases of PEMC, PEC (perfect electric conductor) and PMC (perfect magnetic conductor) cores have been computed and compared. The behavior of the monostatic echo width with the variation of the admittance parameter for the co-polarized and the cross polarized fields is also investigated. The comparisons of the computed results of the presented formulations with the published results of some special cases confirm the accuracy of the presented analysis.     

Electromagnetic scattering by a helical sheath

The harmonic-series solution for the scattering by a unidirectionally conducting helical sheath is obtained when the medium external to the sheath is different from the internal one. The expressions for the scattering cross-sections and surface charge density are also given.     

Two-dimensional scattering by a homogeneous anisotropic rod

An integral equation based on a plane wave representation of the fields in a simply connected and anisotropic medium has been derived in order to handle the problem of two-dimensional scattering by a homogeneous anisotropic cylinder. Its simplicity: one-dimensional, finite range of integration, one unknown with no derivatives of it involved, and a nonsingular kernel, results in an efficient and straightforward numerical implementation. Both polarizations are considered and computer results are presented, discussed, and used to check our scheme thoroughly.     

任意截面非均匀各向异性阻抗柱体的电磁散射

采用矩量法(MoM)结合阻抗边界条件研究了二维无限长任意形状截面非均匀各向异性阻抗柱体的电磁散射特性。散射场通过Stratton-Chu电场积分方程、电流连续性方程和二维格林函数予以求解。当柱体截面矢径的模等于恒定值时,目标退化为二维无限长圆柱,提出的计算方法仍然有效。计算得到的散射宽度结果与解析法、物理光学法(PO)的结果进行了比较,吻合良好。     

各向异性阻抗面电磁散射快速数值算法研究

基于多层UV矩阵分解技术,提出用矩量法(MoM)求解三维各向异性阻抗面电磁散射的MoM-UV快速数值算法。根据等效原理,将表面电磁流以RWG(rao-wilton-glisson)矢量基函数展开。引入阻抗边界条件(IBC),以表面阻抗并矢表征电磁参数,实现各向异性阻抗面的电磁仿真。通过多层UV进行低秩矩阵压缩,减少矩阵-向量积运算和内存需求,利用稳定的双共轭梯度(BICGSTAB)迭代方法求解。给出典型算例,并与Mie级数解等精确结果比较,验证该算法的精度和效率。     

Electromagnetic scattering by a thin resistive wire

A theoretical investigation concerning scattering of a plane electromagnetic wave by a straight resistive wire of finite length in an isotropic homogeneous medium is reported. The work is based on the travelling-wave solution obtained by repeated use of the Wiener-Hopf method. Some numerical data for backscattering cross-section at broadside incidence are given.     

Electromagnetic scattering by a straight thin wire

The traveling-wave energy, which multiply diffracts on a straight thin wire, is represented as a sum of terms, each with a distinct physical meaning, that can be individually examined in the time domain. Expressions for each scattering mechanism on a straight thin wire are cast in the form of four basic electromagnetic wave concepts: diffraction, attachment, launch, and reflection. Using the basic mechanisms from P.Ya. Ufimtsev (1962), each of the scattering mechanisms is included into the total scattered field for the straight thin wire. Scattering as a function of angle and frequency is then compared to the moment-method solution. These analytic expressions are then extended to a lossy wire with a simple approximate modification using the propagation velocity on the wire as derived from the Sommerfeld wave on a straight lossy wire. Both the perfectly conducting and lossy wire solutions are compared to moment-method results, and excellent agreement is found. As is common with asymptotic solutions, when the electrical length of wire is smaller than 0.2 λ the results lose accuracy. The expressions modified to approximate the scattering for the lossy thin wire yield excellent agreement even for lossy wires where the wire radius is on the order of skin depth     

Electromagnetic scattering from conducting circular cylinders inthe presence of a stratified anisotropic medium-TM case

Scattering by a conducting circular cylinder in the presence of a stratified ferrite medium is investigated analytically using a combined Green's function (G-function) and integral equation approach. The incident plane wave is polarized along the axis of the cylinder. The bias DC magnetic field is in the same direction. The G-function of the structure is developed by well-known techniques of matrix analysis, and the appropriate integral equation for the electric field is derived on the basis of the modified reciprocity theorem. Its solution is followed by numerical results presented in graphical form for both the current density induced on the scatterer's surface and the scattered far field. The possibility of controlling the scattering properties of the structure by varying the degree of anisotropy is also investigated. The main conclusion is that anisotropic materials can be used to control antenna radiation characteristics     

使用直角棱镜耦合器的新方法

利用直角棱镜耦合器,实现了同时激励波导模的传输条纹和m-线,从而使它兼有对称棱镜耦合器的耦合特性。进行了理论分析,并给出测试方法及测量结果。     

Electromagnetic scattering from nonlinear anisotropic cylinders. I.Fundamental frequency

The solution of the problem of electromagnetic scattering of obliquely incident plane waves by homogeneous, nonlinear anisotropic cylindrical structures is obtained. The medium of the scatterer is characterized by Volterra-type integrals for the electric and magnetic flux density vectors D and B, respectively. The nonlinear problem is solved using the perturbation method. The effects of nonlinearities on the field properties both inside and outside the scatterer, together with the effect on the radar cross section, are investigated for the fundamental frequency components. To demonstrate the validity of the approach, the results obtained by the perturbation method are compared with those obtained using the plane wave representation method of D. Censor (1983), where the iteration method is used to solve the resulting dispersion equation. The results are in very good agreement in both amplitude and phase of the fields for the case of very weak nonlinearity. When the relative magnitude of the nonlinear component of the permittivity is increased, the iteration method shows a faster divergence of the phase from the linear phase     

Electromagnetic scattering by indented screens

The problem of three dimensional electromagnetic scattering from a perfectly conducting screen with a bounded indentation is formulated as a system of boundary integral equations for the electric current density on the cavity wall and the interface between the cavity and free space. It is shown how the fictitious current density on the interface may be eliminated resulting in an integral equation of the second kind for the current density on the cavity wall only, with no integration over the infinite screen. In addition, integral representations are derived that represent the field everywhere in space in terms of the current density on the cavity wall only. Furthermore, asymptotic expressions for the far field are also presented. The equations and representations simplify considerably in the two-dimensional scalar case and results are presented for both TE and TM polarization     

Electromagnetic scattering by a cylinder with an inhomogeneous sheath

This letter deals with a perfectly conducting infinitely long circular cylinder coated with a radially stratified sheath. Scattering of normally incident plane electromagnetic waves is considered. A certain profile of permittivity in the sheath is taken, leading to particularly simple results.