二维导体微粗糙面与其上方金属平板的复合电磁散射研究

研究了二维导体微粗糙面与其上方金属平板复合电磁散射特征.应用互易性原理使求解二次散射场简化为求解包含平板上的极化电流和微粗糙面散射场的积分方程，从而降低了求解难度.应用物理光学近似和微扰法分别求解了平板上的极化电流和粗糙面的电磁散射场，得到了复合散射截面计算公式并进行了数值计算.尤其对该复合模型后向耦合电磁散射结果进行了详细分析和讨论. 关键词： 互易性原理 复合电磁散射 微粗糙面 平板     

Electromagnetic beam wave scattering by arbitrary cross-sectional conducting cylinder using N circular cylindrical models

Rigorous expression of the electromagnetic beam wave scattering by N circular cylindrical models is described. To check this method, comparison between exact solution and this model composed of N=24 circular cylinders is presented for a single circular conducting cylinder. Numerical results of conducting square cylinder has been also checked with well-known result (B.E.M).     

三维目标与粗糙面复合散射的广义稀疏矩阵平面迭代及规范网格算法

提出了快速计算二维导体粗糙面与面上金属目标复合散射的广义稀疏矩阵平面迭代及规范网格法(G-SMFSIA/CAG).推导了二维导体粗糙面与面上目标相互作用的耦合积分方程,用稀疏矩阵平面迭代及规范网格法(SMFSIA/CAG)求解粗糙面部分的表面积分方程,而用基于RWG基函数的矩量法(MOM)计算目标部分的表面积分方程,并通过更新方程的激励项迭代求解目标与粗糙面的相互耦合作用.结合Monte-Carlo方法产生具有PM(Pierson-Moskowitz)海浪谱的随机海洋粗糙面,数值分析了海面上不同形状导体目 关键词： 复合散射 广义稀疏矩阵平面迭代及规范网格法 随机海洋粗糙面 双站散射系数     

拓扑绝缘体椭球粒子的电磁散射

利用麦克斯韦方程组,用球矢量波函数展开了长椭球坐标系中的电磁场分量; 根据拓扑绝缘体的本构关系,修正了椭球内外的电磁场;利用拓扑绝缘体的边界条件, 推导了散射系数和散射电磁场.模拟结果表明:当时间反演对称打破时,拓扑磁电参数对散射截面有明显影响.     

Electromagnetic scattering from two-layered rough interfaces with a PEC object: vertical polarization

Electromagnetic(EM) scattering from a stack of two rough interfaces separating a homogeneous medium with a perfectly electric conducting(PEC) object has been calculated through the method of moments for vertical polarization.Theoretical formulations of EM scattering from multi-layered rough interfaces with a PEC object have been derived in detail and the total fields and their normal derivatives on the rough interfaces are solved.The two-layered model is a special case.In this work,a Gaussian rough surface was applied to simulate the rough interface.A cylinder was located above,between or below the two-layered rough interfaces.Through numerical simulations,the validity of this work is demonstrated by comparing it with existing scattering models,which are special cases that include a PEC object located above/below a single-layered rough interface and two-layered rough interfaces without an object.Subsequently,the influences of characteristic parameters,such as the relative permittivity of the medium,as well as the average height between the two rough surfaces,on the bistatic scattering coefficient are discussed.     

Electromagnetic scattering from two parallel 2D targets arbitrarily located in a Gaussian beam

In this paper based on the equivalence principle and the reciprocity theorem, the scattered field up to second-order by two parallel 2D targets arbitrarily located in a Gaussian beam is considered. The first-order solution can easily be obtained by calculating the scattered field from isolated targets when illuminated by a Gaussian beam. However, because of the difficulty in formulating the couple scattering field, it is almost impossible to find an analytical solution for the second-order scattered field if the shapes of 2D targets are not canonical geometries. In order to overcome this problem, in this paper, the second-order solution is derived by using the technique based on the reciprocity theorem and the equivalence principle. Meanwhile, the relation between the secondary scattered field from target #1 and target {\#}2 is obtained. Specifically, the bi- and mono-static scattering of Gaussian beam by two parallel adjacent inhomogeneous plasma-coated conducting circular cylinders is calculated and the dependence of attenuation of the scattering width on the thickness of the coated layer, electron number density, collision frequency and radar frequency is discussed in detail.     

应用改进的物理光学法和图形计算电磁学近似算法快速计算导体目标电磁散射特性

结合改进的物理光学法和图形计算电磁学法实现了考虑边缘绕射情况下复杂目标的高频电磁波散射的高效且精确求解.传统的考虑边缘绕射的物理光学算法不能直接计算出目标的雷达截面,它需要先计算绕射贡献,然后加上物理光学的散射贡献,最终才能得到目标的雷达截面.通过运用改进的物理光学法对图形计算电磁学法进行修正,直接修正表面法向量,从而修正了表面电流,这样就考虑了边缘处的绕射,提高了算法的效率.这不但充分利用了计算机硬件优势,借助于计算机显示技术,由图形加速卡完成最困难、最费时的消隐工作,而且利用图形计算电磁学的积分公式,将三维空间的积分转化为屏幕像素的二维空间积分,使得计算大幅简化.数值结果表明了所提出方法的精确性和高效性.     

二维高斯波束对多层球粒子电磁散射的解析解

基于矢量波函数在球和柱坐标系中表达式之间的转换关系,提出了一种求解球坐标系中二维高斯波束波形因子的方法,得到了二维高斯波束波形因子在球坐标系中的解析公式.结合广义米理论推导了在轴二维高斯波束入射多层球粒子的电磁散射的解析解,并对散射强度随散射角的分布进行了数值模拟,结果与平面波入射情况进行了比较. 关键词： 矢量波函数 波形因子 电磁散射 广义米理论     

畸形波电磁散射特性分析及其特征识别标识的研究

针对弱非线性的Longuet-Higgins模型在模拟强非线性畸形波海面时所存在的问题,采用修正的相位调制法模拟一维畸形波时间、空间波面,该方法能够实现畸形波的定时定点生成,并且其波形既能保持目标谱的频谱结构,又能较大程度地满足波浪序列的统计特性.同时,基于改进的双尺度(TSM)法及时域有限差分法建立畸形波的电磁散射模型,经过相对平均偏差和均方根偏差误差分析后,基于TSM法研究分析了畸形波及其背景海面波的归一化雷达散射截面(NRCS)的计算结果.实验表明,合成孔径雷达成像中畸形波的NRCS比背景波要小,即畸形波的合成孔径雷达图像成像比背景波要灰暗,因此可以将NRCS作为畸形波的特征识别标识.通过分析研究不同极化方式、入射角、入射频率条件下畸形波与背景波面的电磁散射特性实验数据得出:当二者的NRCS差值大于-11.8 dB及以上时,即认为产生畸形波,这为实际的工程应用提供了参照标准.     

A study of radiation from circular groove guide horn

A novel horn antenna for millimeter waves based on circular groove guide is presented and investigated in this paper. Its radiation patterns are calculated by employing the aperture field method. The patterns obtained by experiment show agreement with calculated results.     

Pure elastic resonance scattering of an obliquely incident plane acoustic wave by a submerged infinite cylinder

I.IntroductionTheResonanceScattcringThcory(RST)asanimportantmethodtoana1yzeacousticscat-teringofsubmergede1asticbodieswascxtcnsivelyuscdforcy1indrica1andspherica1geometries,inc1udingsolidstructuresandho11owoncs.RSTismain1yappliedtostudytheresonancescat-teringspcctra(oracousticspcctra)ofanc1astictargctcxcitedby'theinciderttacousticwavesoastOidentifythetargct.Tocxtracttheresonancescattcringspcctra,anappropriatebackgroundsuchasrigidbackgroundorsoftonemust-besubtractcd.Expcrimenta1ly,theReson…     

平行柱体对平面波/高斯波束电磁散射

基于等效原理和互易性定理，研究了N个相互平行二维柱体对平面波/高斯波束的电磁散射特性，给出了求解N阶散射场公式.一阶散射可通过求解单个柱体的散射场得到，但对于高阶散射场而言，由于耦合散射的复杂性，很难给出精确的解析解.为了解决这一问题，借助等效原理和互易性定理给出了求解N阶散射场的面积分公式.只要给出柱体的i-1阶散射场及相关目标表面上的等效电流和(或)等效磁流，就可应用此公式求解i阶散射场.应用该近似方法计算了相互平行非均匀等离子体涂层导体圆柱的单/双站散射宽度，讨论了束腰半径、等离子体涂层厚度、电子密度、碰撞频率及雷达频率等对散射结果的影响.     

High-Frequency Gravitational Waves in Electromagnetic Waveguides

The interaction between a very-high-frequency gravitational wave (VHFGW) and an electromagnetic wave (EMW) in a rectangular waveguide is discussed in the weak field limit. The background EMW is assumed to be initially in the TE₁₀ mode along the waveguide. It is then shown that a VHFGW, having the same frequency and direction of propagation of the EMW, induces through the waveguide a TE mode with a frequency doubled when compared to the original EMW frequency. In that respect, the GW acts similar to a non-linear medium, giving rise to a Second Harmonic Generation (SHG) effect.     

有限元/边界积分方法在海面及其上方弹体目标电磁散射中的应用

本文将有限元/边界积分方法(FE/BIM)结合区域分解方法引入到粗糙海面及其上方目标 的电磁散射问题的研究中. 由于积分边界可以以任意形状设置在距模型表面任意远的距离处, 故本文采用共形人工边界结合区域分解建模方法截断模型的开放计算区域以减少求解未知量, 在截断区域内部采用有限元方法求解, 而计算区域的边界条件通过边界积分方程方法得到. 通过与矩量法获得的数值计算结果进行比较, 证明了该混合算法及模型处理方法的正确性, 进而研究了海面上方弹体目标的电磁散射特性, 并讨论了其双站散射系数随电磁波入射角度、目标高度、海面风速以及弹体尺寸的电磁散射特性变化情况. 本文结果可用于反演复杂背景下的目标信息及目标探测等领域. 关键词： 电磁散射 粗糙海面 目标 有限元/边界积分方法     

The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction

The relation between corresponding trigonometric functions in two rotating coordinate systems is presented. The transformation formula for a vector in the two rotating spherical coordinate systems is obtained. The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction are derived. These fields in a particular case retrogress to those available in the literature. The obtained results have great potential in practical applications.     

有ITO透明导电膜的平面分层介质系统的电磁波性能理论研究

理论研究了有ITO(indium tin oxide)透明导电膜的多层平面分层介质系统的电磁性能，给出的理论曲线和实测曲线符合很好.多层平面分层介质系统的电磁性能与ITO膜(方块电阻为8Ω)所在界面位置和平面分层介质系统层数及各层厚度等有关.优化设计了一种含有ITO透明导电膜的厚度仅7.35mm的四层平面分层介质系统，其在8—18GHz频段内电磁波反射性能很好.作为多层平面分层系统中的ITO导电膜，其方块电阻应低于30Ω，并且越小，其反射性能越好. 关键词： 多层平面介质系统 电磁性能 ITO透明导电膜     

Rigorous and approximate methods for modeling wave scattering from a locally perturbed perfectly conducting surface

Rigorous and approximate methods are considered for solving the problem of harmonic plane wave scattering from a plane surface arbitrarily perturbed along one dimension on a finite interval. This problem is treated using the Fredholm integral equations of the second kind and the Kirchhoff and Rayleigh approximations. The estimates of the computational efficiency of the integral equation method and the Rayleigh approximation are compared by calculating fields scattered from random rough surfaces in the resonance region (i.e., when the roughness height is comparable to or smaller than the incident wavelength) for an arbitrary incidence of a plane wave. Scattering patterns calculated using the integral equations and the Kirchhoff approximation are discussed in the case of large-scale random rough surface scattering. Particular attention is paid to scattering at near-grazing incidence.     

Resonant Raman scattering from a spin density wave insulator

We present a calculation of the electronic Raman cross section for the scattering of light across the energy gap of an antiferromagnetic insulator. The antiferromagnet is described in terms of a spin density wave state for the Hubbard model at half filling. We consider the coupling of the light to the current density and the inverse mass tensor on equal footing. A comparison of the cross section for different scattering geometries is given.     

金属/介质涂覆的S形扩压器电磁散射特性

进气道作为飞机强散射源之一,准确评估其雷达散射截面(RCS)特性一直是当今计算电磁学的研究热点.研究了一种加入阻抗边界条件、前后向迭代的迭代物理光学法,提出一种盒体分割法用于处理几何消隐工作.通过软件开发实现任意金属/介质腔体RCS特性评估,并用相关算例校验软件准确性.在此基础上应用该软件对金属/涂敷介质矩形S弯扩压5器进行数值模拟,获得了扩压器在入射波长0.03 m下的RCS变化规律.改进后的迭代物理光学法适用于任意腔体改型和涂敷吸波材料研究,缩短设计周期.