基于FE-BI的介质粗糙面上方涂覆目标电磁散射特性研究

采用有限元-边界积分（finite element boundary integral,FE-BI）方法研究了介质粗糙面上方涂覆目标的复合电磁散射特性,推导了一维介质粗糙面上方二维涂覆目标电磁散射的FE-BI公式.在仿真中,采用功能强大的有限元方法模拟涂覆目标内部场,对于涂覆目标与粗糙面之间的多重耦合作用则通过边界积分方程方法进行考虑.结合Monte-Carlo方法,数值计算了介质高斯粗糙面上方涂覆圆柱目标的电磁散射,分析了涂层材料介电常数、粗糙面粗糙度以及介质粗糙面介电常数变化对复合模型双站散射系数的影响.数值结果表明,相比于传统矩量法（method of moment,MoM）,本文方法虽然在处理理想导体模型时效率略低,但可以处理MoM难以处理的复杂媒质电磁散射问题,且计算精度较高.     

一种大型阵列天线散射特性快速计算方法

:针对大型阵列天线的散射特征,提出了一种基于区域分解方法计算大型相控阵天线散射特性的快速计算方法,将相控阵天线的散射计算问题分解为求解反射板和辐射天线阵列两个子区域的问题,使以前不能在PC机上计算大型阵列天线的散射问题得以解决,并且计算速度快。该方法已经在工程中得到应用,通过与实测数据进行对比,计算精度可以达到±1 dB 以内。该方法在保证计算精度的同时可以大大降低计算复杂度,极大地提高了计算效率,为大型相控阵天线RCS预估提供了一种高效、可靠的解决方法。     

卫星目标电磁散射的高效区域分解边界积分法

近年来，严峻的空天安全问题致使卫星的电磁散射特性分析与控制倍受关注.典型卫星主要由主体、太阳翼和多用途天线等部件组成，呈现多尺度的几何特性，给电磁建模技术带来了挑战.面向卫星的电磁散射特性分析，本文采用不连续伽辽金区域分解积分方程（discontinuous Galerkin domain decomposition method of integral equation,DG-DDM-IE）方法构建准确且灵活的计算模型，并基于以往对角区域块（diagonal domain block,DDB）预条件和稀疏近似逆（sparse approximate inverse,SAI）预条件的数值性能研究结果，针对多尺度情况提出一种经济高效的混合型预条件以提高DG-DDM-IE方法的计算能力.复杂多尺度卫星目标数值实验证明，该DG-DDM-IE方法在消耗较少内存的条件下仍保证良好的收敛性和可扩展性.     

快速多极子在任意截面均匀介质柱散射中的应用

采用快速多极子法（FMM）加速后的矩量法（MoM）求解由电磁场等效原理导出的关于均匀介质柱表面等铲电磁流的积分方程,进而计算其电磁散射特性,FMM的引入使计算时间和内存开销都从O(N^2）降到O（N^3/2）,且并不增加多少复杂度。最后给出了一些介质柱体RCS的算例。     

舰载相控阵天线杂散发射辐射的统计电磁学分析

舰船上的有源相控阵天线各个单元收发组件的杂散发射及其辐射的电磁环境电平是典型的随机量,无法直接 利用适合于确定性问题的计算电磁学方法进行求解。本文建立了舰船环境下相控阵天线的电磁仿真模型,应用电磁场全波分 析结合蒙特卡洛方法的数值统计电磁学方法,分析了舰载相控阵天线杂散干扰的随机特性,给出了相控阵天线杂散发射辐射 的环境电场值随着各个天线单元杂散发射随机特性变化的概率密度统计分布。该方法对于其他随机因素引发的相控阵天线 指标的统计特性分析也具有参考意义。     

典型相控阵雷达电磁时空分布仿真系统设计

针对相控阵雷达的功能特点,设计了一种可以仿真典型相控阵雷达电磁时空分布的系统。该系统主要分为相控阵天线性能仿真模块和典型相控阵雷达功能仿真模块两个部分。其中相控阵天线性能仿真模块可以模拟各类相控阵天线的方向图;典型相控阵雷达功能仿真模块可以模拟宙斯盾、爱国者等相控阵雷达的电磁时空分布特性。     

主动雷达导引头地面雷达站识别技术研究

该文针对主动雷达导引头对地面防空单元制导雷达站的识别问题,在天线电磁散射特性研究的基础上,提出了雷达天线的多特征融合识别算法。首先对相控阵雷达天线的电磁散射特性进行了建模和计算,然后采用多普勒波束锐化技术对目标进行2维成像以提高天线的检测概率并估计目标雷达天线的RCS序列,基于RCS序列的幅度特性与周期特性,构造了相控阵天线的4类特征,并提出了相应的识别算法及融合识别算法。仿真实验表明算法具有较高的识别概率。     

时域有限差分电磁建模系统的研究与设计

基于时域有限差分（FDTD）算法并利用计算机可视化技术，对目标系统进行电磁建模研究，并设计出一套具有丰富内建图形处理功能的网格生成软件。在本系统中通过对目标系统进行3D建模和电磁学问题描述，将生成的电磁建模文件输入FDTD仿真模块即可进行模拟分析计算，直观形象地观察到电磁场的分布状态、电磁波传播、透射、散射等现象。U型天线的建模实例表明该电磁建模系统准确、高效。     

埋地二维柱体的电磁散射

本文利用进域有限差分（ＦＤ－ＴＤ）方法分析计算了正弦平面波照射下埋地二维金属柱体的电磁散射特性，给出了柱体上的感就电流值和地面上方近场区的电磁场值。讨论了有耗介质中差分网格的数值色散特性和吸收边界条件。通过将本文用ＦＤ－ＴＤ计算结果与其它数值结果进行比较，证实了ＦＤ－ＴＤ方法在分析有耗介质中电磁散射问题的有效性。     

一种基于不连续伽辽金方法求解多区域目标散射问题的优化预处理器

在电磁散射问题中,由均匀介质和金属组合而成的多区域结构目标在天线仿真、雷达成像等工程问题中有着广泛应用. 针对多区域目标的散射问题,研究了不连续伽辽金（discontinuous Galerkin, GD）方法在多区域面积分（surface integral equation, SIE）矩量法中的使用,同时提出了一种优化的距离稀疏预处理（optimized distance sparse preconditioner, O-DSP）方法。该方法根据阻抗矩阵中不同积分算子随距离变化的特性来个性化选择预处理矩阵,进一步增加了预处理矩阵的稀疏性. 数值计算表明,相比之前的距离稀疏预处理方法,优化的预处理矩阵非零元素仅为以前的一半,而且具有相同加速迭代效果.     

A Generalized Surface Integral Equation Formulation for Analysis of Complex Electromagnetic Systems

A novel method is presented to analyze the electromagnetic characteristics of systems consisting of a large number of scatterers with different shapes and materials. In the method, nearly located scatterers are grouped together, while large bulk materials are divided into subblocks with adequate sizes. A scatterer group or a subblock forms a basic block of the system, and each block is contained with a virtual reference surface. A generalized transition matrix defined on the reference surface is used to characterize the electromagnetic characteristics of the block. The generalized transition matrix relates the rotated tangential components of the scattered fields or the equivalence sources to the rotated tangential components of the incident fields directly. The generalized transition matrix can be calculated for each block independently using proper methods according to its structure and material. Surface integral equations are established on all the virtual reference surfaces, which can be solved by moment method to get the electromagnetic characteristics of the whole system. Characteristic basis functions and synthetic basis functions can be applied to further reduce the unknown number, while fast multipole method can be used to accelerate the evaluation of interactions. Two-dimensional examples are provided to verify the method.     

电磁散射的拉格朗日乘子区域分解算法

针对电磁散射问题,提出了一种基于广义变分原理的区域分解算法.将原求解区域划分为若干个不重叠的子区域,引入拉格朗日乘子法以满足相邻子区域之间场的连续性要求,并建立其修正泛函,使原问题转化为求解拉格朗日乘子.研究了子区域系数矩阵的可逆性.为了进一步提高效率,采用了重启的广义最小残量法为求解器.数值算例验证了本文方法的准确性和有效性.     

On iterative approaches for electromagnetic rough-surfacescattering problems

Iterative techniques developed for solving general systems of linear equations have been applied to systems resulting from electromagnetic rough-surface scattering problems. Previously used iterative procedures that model the multiple scattering of the electromagnetic energy are shown to be mathematically equivalent to the application of stationary iterative procedures to the system of equations resulting from the standard moment method. Convergence difficulties that are sometimes observed with these approaches are due to the inherent limitations of the stationary techniques. The performances of the stationary approaches are compared with that of several conjugate-direction-based nonstationary iterative procedures through the application to a series of scattering surfaces that yield rapidly changing conditioning of the moment method interaction matrix. The stationary algorithms give the quickest convergence when applied to the systems with the best conditioning, but the nonstationary techniques prove much more robust in other more ill-conditioned situations     

GIM 技术在二维介质散射中的应用*

如何利用散射体的几何对称性,使各种矩阵方法求解电磁散射问题所需的存储量和计算时间减少,是当前计算电磁学领域中具有理论和实际意义的重要课题.本文针对谐振频段的TM波对介质柱体的散射问题,采用矩阵方法与GIM(广义镜像法)技术相结合的算法,通过构造虚拟的对称源与反对称源和运用叠加定理,成功地将原问题的求解转化为只在其1/4的边界上进行求解,由此达到了减少矩阵元和节约运算时间的目的.通过理论分析和具体算例的检验,并与MOM计算结果比较,证实了该方法在节约计算时间方面有显著优势.     

The use of the FFT for the efficient solution of the problem ofelectromagnetic scattering by a body of revolution

The enhancement of the computational efficiency of the body of revolution scattering problem is discussed with a view of making it practical for solving large body problems. The problem of the electromagnetic scattering by a perfectly conducting body is considered, although the methods provided can be extended to multilayered dielectric bodies as well. Typically, the generation of the elements of the moment method matrix consumes a major portion of the computational time. It is shown how this time can be significantly reduced by manipulating the expression for the matrix elements in a manner that allows one to compute them efficiently by using the fast Fourier transform (FFT). A technique for extracting the singularity of the Green's function that appears within the integrands of the matrix diagonal is also presented, further enhancing the usefulness of the FFT. It is shown that, with the use of the method discussed here, the computational time can be improved by at least an order of magnitude for large bodies in comparison to that for previous algorithms     

边界积分法及连接算法分析任意腔体的散射

本文利用边界积分法分析二维任意腔体的散射,给出一种基于微波网络原理的连接算法,将腔体分为几段,分别用积分方程法计算每段的广义导纳矩阵,然后利用连接算法将各段连接,得到整个腔体的口径导纳矩阵,最后由广义网络原理求解腔体的等效磁流及后向散射场。本文方法可作为一种机辅设计算法。     

多导体散射中广义谐振的模式分析

在电磁兼容分析中,多导体开放系统中存在的广义谐振现象是一个值得注意的问题.本文利用矩量法分析了多导体散射问题,发现了广义谐振现象,并提出广义谐振腔模型,对广义谐振进行了模式分析,很好地解释了这类散射结构的谐振特性.     

RF radiation properties of printed-circuits boards in a GTEM cell

The behavior of reradiated fields from printed-circuits boards (PCBs), with the radar cross section being the main parameter of interest, is investigated in this paper. A rigorous approach to predict radiation from PCBs in a gigahertz transverse electromagnetic cell is presented. The analysis is based upon the use of the reciprocity theorem in combination with the method of moment applied to the scattered field, thus yielding a generalized impedance matrix, whose determinant represents the characteristic polynomial of the scattering system. The effectiveness of the method is demonstrated by investigating some canonical circuit configurations and structures illustrating sources of fundamental electromagnetic interference mechanism. The validity and the accuracy of the analysis becomes obvious in view of the one-to-one correlation with measurements.     

有限厚导电平板上任意缝隙的耦合特性分析

利用边界积分方程法结合广义网络原理和连接算法分析了有限厚导电平板上任意二维缝隙的散射及传输特性,并以ＴＥ波为例给出了具体的分析方法和结果。该方法不仅可用于任意形状和复杂介质填充缝隙的分析,还可考虑缝所在导体板的厚度。边界积分方程和连接算法的采用,使得分析该问题所需的计算机容量大大降低,计算效率大大提高。     

双屏频率选择表面传输特性的研究

应用广义散射矩阵和矩量法对双屏圆环单元频率选择表面(Frequency Selective Surfaces简称FSS)、双屏Y环单元FSS和双屏Y孔单元FSS的传输特性进行了数值计算及分析.采用镀膜和光刻技术制备出相应单元图形的单屏FSS,利用精密装配技术将两单屏FSS进行装配,制备出相应的双屏FSS实验件;在微波暗室内用矢量网络分析仪测试了双屏FSS的传输系数,测试值与数值结果基本一致.结果表明:双屏FSS的传输系数曲线具有宽带宽和陡降截止的频率特性,其电磁散射特性较单屏FSS有很大的改善.