基于Inagaki模式方法分析导体内谐振特性

当应用电场积分方程或磁场积分方程对导体散射特性进行矩量法分析时,在某些离散的频率点即内谐振点上,常常出现解的不稳定或不唯一情况。为了解决这一问题,该文提出了一种新型的消除内谐振的方法。这种方法基于电场积分方程,利用Inagaki模性质有效地去除了谐振模式,获得内谐振条件下正确的导体散射特性。该方法具有概念清晰和计算简便等优点。计算结果与公开发表的文献结果以及解析解相比,一致性良好。     

基于奇异值分解的方法求解目标内谐振时的散射截面

表面积分方程已被广泛地用来分析电磁散射问题,但在离散的内谐振频率点上,用矩量法求解积分方程将得到错误的结果.本文基于电场积分方程,应用奇异值分解找出谐振模电流,并采用正交化方法将其舍去,从而得到非谐振模电流的分布.文中计算了一无限长理想导体圆柱内谐振时的散射截面,所得结果与解析解一致,并对一无限长理想导体三角柱的前向散射截面进行了计算,结果表明本文方法是有效和准确的.     

一种求解目标内谐振时散射截面的有效方法

众所周知,在内谐振频率点上,用矩量法求解电场或磁场表面积分方程将得到不正确的表面电流。文中应用奇异值分解和正交化方法对由电场积分方程计算出的表面电流进行修正,从而得到目标表面上产生散射场的真实电流分布。文中计算了一无限长理想导体圆柱内谐振时的散射截面,所得结果与解析解一致,并对一无限长理想导体正方柱的后向散射截面进行了计算,结果表明本文方法是有效和准确的。     

埋于介质体中二维导体目标成象的迭代方法

本文应用一种迭代方法实现了埋于二维均匀介质体中理想导体目标几何构形的重建。在导出介质体与导体混合目标散射边界积分方程的基础上，利用Ｎｅｗｔｏｎ－Ｋａｎｔｏｒｏｖｉｃｈ方法和矩量法建立逆散射基本方程。为克服病态问题，连续采用多方面ＴＭ平面波照射目标以获取足够的信息，并通过迭代方法求解。最后、给出的一些散射目标的重建结果表明本方法的可行性，同时研究了噪声对重建结果的影响。     

内谐振条件下导体散射特性的双正交模法分析

众所周知，当我们应用积分方程，不论是电场积分方程还是磁场积分方程，去分析导体的散射特性时，在内谐振条件下将出现解答的不唯一性或不稳性问题，给计算工作带来严重的困难。本文提出的双正交模分析方法有效地克服了这一困难，且该方法具有使用简单和概念清晰的优点。若干数值计算实例表明了该方法的正确性和有效性     

基于共轭梯度法的三维标量激光漫反射特性

为了提高通信质量,改善舰队内部通信的保密安全性能,针对激光点对点通信方式的不足,提出了利用海面作为激光漫反射媒介进行组网通信的设想。为了得到更为准确的数值仿真结果,根据麦克斯韦尔方程结合理想导体界面的边界条件,对激光入射理想导体表面后产生的散射场进行了研究。首先,利用三维标量锥形波对入射激光束进行了模拟;然后,列出了积分方程,并根据矩量法进行了离散;最后,通过共轭梯度法求解矩阵方程,得出了三维散射系数,准确地表示了基于理想导体界面的三维标量激光漫反射特性,为进一步研究三维激光海面漫反射特性奠定了基础。     

E-P-AMCBFM分析介质与PEC混合体的电磁散射

使用基于表面积分方程的矩量法来分析介质与理想导体混合体的电磁散射是计算电磁学的一大热点。对理想导体目标体表面建立电场积分方程,在介质目标体表面建立PMCHW方程组,与基于矩阵分块技术的自适应修正特征基函数法结合,对介质涂敷理想导体目标体的电磁散射进行分析,将其称之为EFIE-PMCHW-AMCBFM(E-P-AMCBFM)。并讨论不同参数如基函数阶数,矩阵块间重叠区域等对计算效率的影响,数值结果表明E-P-AMCBFM对于处理介质-理想导体混合体的电磁散射问题具有较高的精度和效率。     

内谐振条件下导体散射特性的双正交模法分析

众所周知，当我们应用积分方程，不论是电场积分方程还是磁场积分方程，去分析导体的散射特性时，在内谐振条件下将出现解答的不唯一性或不稳性问题，给计算工作带来严重的困难。本文提出的双正交模分析方法有效地克服了这一困难，且该方法具有使用简单和概念清晰的优点。若干数值计算实例表明了该方法的正确性和有效性。     

基于理想导体界面的三维激光漫反射特性

针对激光点对点通信方式的不足,提出了利用海面作为激光漫反射媒介进行组网通信的设想,并对激光入射理想导体表面后产生的散射场进行了的研究。首先利用三维锥形波对三维入射激光束进行了模拟;然后对散射场在各个方向上的分量之间的耦合关系进行了研究,并列出矩阵方程;最后通过结合格林函数谱积分加速算法的前后向迭代法求解矩阵方程,得出三维散射系数,准确的表示了基于理想导体界面的三维激光漫反射特性,为进一步研究三维激光海面漫反射特性奠定了基础。     

部分覆盖介质导体柱的电磁散射研究

本文通过建立积分方程并利用矩量法,解决了部分涂覆介质导体柱的电磁散射问题。有关的计算程序成功地实现了通用化,即集导体柱、介质柱、全部及部分覆盖介质的导体柱的计算程序为一体。实例计算表明,该程序在计算目标雷达散射特性方面具有较高的实用价值。     

Combined field integral equation formulation for scattering by dielectrically coated conducting bodies

The combined field integral equation (CFIE) formulation for electromagnetic scattering from perfectly conducting bodies is generalized to treat conductors with layered dielectric coatings. The generalized formulation is proved to provide unique solutions at all frequencies. The method of moments is used to solve the resulting system of integral equations. Solutions in terms of two integral operators are developed for body of revolution configurations. The behavior and properties of the generalized combined field formulation are illustrated with results of calculations for coated spheres, cylinders, and cones.     

Hybrid numerical method for harmonic 3-D Maxwell equations:scattering by a mixed conducting and inhomogeneous anisotropicdielectric medium

This article deals with a hybrid numerical method for solving harmonic Maxwell equations in the classical electrodynamic context. This formulation can be used with any body of arbitrary three-dimensional geometry, of perfectly conducting material or dielectric, with locally inhomogeneous and anisotropic behavior laws, and with or without dielectric losses. The mathematical formulation is presented along with applications validating it. The exterior problem is treated by the integral equation method while local equations are used for the dielectric parts of the body. A global variational formulation of the coupled problem is developed for use in discretization by the finite element method. Boundary finite elements are used for integral operators connected with the exterior problem. Localized finite elements are used for the interior problem. Difficulties of irregular frequencies, also called resonant frequencies in the perfectly conducting case, arising from the integral formulation are analyzed in detail and an efficient solution is developed     

Extended integral equation formulation for scattering problems froma cylindrical scatterer

An extended integral equation is developed for electromagnetic scattering from a perfectly conducting cylinder and a dielectric cylinder. The conventional surface integral equations cannot yield unique solutions when the wavenumber of the electromagnetic wave is equal to an eigenwavenumber of the system. Several methods to overcome this difficulty have been presented, but each method includes some drawbacks. A numerical method is proposed in which the boundary element method is applied to the extended integral equations with the observation points lying on a closed surface inside the scatterer. It is shown that the extended integral equations have unique solutions for any given wavenumber. As examples, plane wave scattering from a perfectly conducting elliptic cylinder, a dielectric elliptic cylinder, and a dielectric rectangular cylinder is numerically analyzed     

Dual-surface integral equations in electromagnetic scattering

A brief review is given of the derivation and application of dual-surface integral equations, which eliminate the spurious resonances from the solution to the original electric-field and magnetic-field integral equations applied to perfectly electrically conducting scatterers. Emphasis is placed on numerical solutions of the dual-surface electric-field integral equation for three-dimensional perfectly electrically conducting scatterers.     

Electromagnetic diffraction from a dielectric-filled slit-cylinderenclosing a cylinder of arbitrary cross section: TM case

A simple moment solution to the problem of the diffraction of a TM plane wave from an infinite, perfectly conducting slotted cylinder of an arbitrary cross section is summarized. The slit cylinder encloses a smaller perfectly conducting cylinder of an arbitrary cross section, and the space between the cylinders is filled with a dielectric material. The equivalence principle is used to obtain a set of coupled integral equations for the induced/equivalent surface currents on the cylinders, and the method of moments is used to solve numerically the integral equations. The electric field integral equation formulation is used. The advantages and the limitations of the method are discussed. Sample results for the induced current, aperture field, internal field, and scattering cross sections are given. These are in good agreement with some of the available published data     

Boundary integral equation technique for the singular behavior ofelectromagnetic fields at the common tip of metallic and bi-isotropiccones with arbitrary cross section

A boundary integral equation technique is developed to determine the singular field behavior at the common tip of lossless bi-isotropic and perfectly electrically and/or magnetically conducting cones with arbitrary cross section. The kernel of the set of boundary integral equations is a Green's function defined on a spherical surface. This Green's function is the associated Legendre function of the first kind. The integral equations are solved with the Galerkin method of moments. The theory is illustrated with a number of examples that show the effects of bi-isotropy on the singular field behavior     

Microwave imaging of multiple conducting cylinders

Inverse scattering for multiple conducting cylinders is investigated. It is assumed that a plane wave is incident upon separate perfectly conducting cylinders of unknown shapes and the scattered field is measured outside, then, using prior knowledge of the rough positions of the scatterers, the shapes of the conducting scatterers can be reconstructed. The Newton-Kanotrovitch method is employed to solve nonlinear integral equations and the pseudoinverse technique is used to overcome the ill-posedness. Numerical examples are given to demonstrate the capability of the inversion algorithm. Good reconstruction is obtained even when the multiple scattering between two conductors is serious. The effect of noise on the reconstruction result is also investigated     

Current induced by TE excitation on a conducting cylinder located near the planar interface between two semi-infinite half-spaces

An analysis is presented for determining the current induced by a known transverse electric excitation on a perfectly conducting cylinder located near the planar interface separating two semi-infinite, homogeneous half-spaces of different electromagnetic properties. The conducting cylinder of general cross section is of infinite extent and the excitation is transverse electric to the cylinder axis. Two types of integral equations, the magnetic field integral equation and the electric field integral equation, are formulated, and the Green's functions for the integral equations are derived in an appendix. Numerical solution methods for solving the integral and integrodifferential equations are presented. For a strip parallel or perpendicular to the interface, a circular cylinder, and a rectangular cylinder, data are presented and discussed for selected parameters, including the case of a cylinder resting on the interface.     

Scattering from narrow rectangular filled grooves

The solution of the integral equation for a small width rectangular groove is considered. It is shown that by retaining the dominant mode supported by the rectangular groove, the resulting quasi-static integral equations are comparable to those associated with the perfectly conducting narrow strip. They are, therefore, amenable to analytic solution yielding the exact field distribution or equivalent currents across the groove's aperture. The derived currents exhibit the same edge behavior as that associated with the currents of a perfectly conducting half-plane. The corresponding current behavior based on a (numerical) impedance simulation of the groove is quite different. However the resulting echowidths are comparable. Both transverse electric (TE) and transverse magnetic (TM) polarizations are treated     

RCS of two-dimensional structures consisting of both dielectricsand conductors of arbitrary cross section

The problem of determining the electromagnetic field scattered by two-dimensional structures consisting of both dielectric and conducting cylinders of arbitrary cross section is considered. The conductors may be in the form of strips and the dielectrics may be in the form of shells. The conductors may be partially or fully covered by dielectric layers, while the dielectrics may be partially covered by conductors. Only homogeneous dielectrics are studied. Both the transverse electric (TE) and the transverse magnetic (TM) cases are considered. The problem is formulated in terms of a set of coupled integral equations involving equivalent electric and magnetic surface currents radiating in unbounded media. The method of moments is used to solve the integral equations. Simple expansion and testing procedures are used. Numerical results for scattering cross sections are given for various structures