介质体电磁散射分析中的等效偶极矩法

在介质体电磁散射分析中,提出了一种基于等效偶极矩法的快速矩阵生成技术。该方法以矩量法和RWG基函数为基础,将源点处的电(磁)流等效为电(磁)偶极子,因而阻抗矩阵元素可以认为是源点电(磁)偶极子所产生的近区场与场点电流基函数之间的相互作用。这样等效偶极矩法避免了格林函数二重积分,使得阻抗矩阵元素的生成速度明显提高。数值结果表明该方法有较高的计算效率和精度。     

用离散复镜像方法计算任意形状微带贴片的散射

采用离散复镜像方法(DCIM)计算微带结构的空间域格林函数，提高了计算阻抗矩阵的速度。采用三角矢量面元(RWG)基函数，模拟电流分布。由于三角形可以模拟任意形状的贴片，本文的方法可以准确地计算任意形状贴片的散射。数值结果证实了本文方法的有效性。     

矩量法分析埋地三维目标的近场电磁散射

采用混合位积分方程（MPIE）和基于RWG基函数的矩量法分析计算了埋地三维目标的近场电磁散射问题,利用二级离散复镜像（DCIM）和广义函数束（GPOF）相结合的方法求解近场Sommerfeld积分,很好地解决了多层媒质中电磁散射计算中的棘手问题,其方法简练、精确、高效,数值分析结果与有关文献吻合很好,证实了该方法的正确性和通用性。此外,该文还通过计算比较了不同观察点、不同目标埋地深度及不同地层媒质参数的电磁散射特性。     

微带印刷天线辐射与散射的全波分析方法

本文给出了一种分析微带印刷天线辐射与散射的数值方法。此方法将印刷天线按三角网格剖分，在导体表面建立积分方程，用全波离散镜像理论给出微带结构的空域格林函数的闭合表达式，未知电流用三角网格上的矢量电流基函数展开并用矩量法求解。与以往的矩形网格上基函数展开相比，此方法能更有效地逼近任意形状的微带结构，最后给出了几个数值结果     

微带印刷天线辐射与散射的全波分析方法

本文给出了一种分析微带印刷天线辐射与散射的数值方法。此方法将印刷天线按三角网格部分，在导体表面建立积分方程，用全波离散镜像理论给出微带结构的空域格林函数的闭合表达式，未知电流用三角网格上的矢量电流基函数展开并用矩量法求解。与以往的矩形网格上基函数展开相比，此方法能更有效地逼近任意形状的微带结构，最后给出了几个数值结果。     

基于时域有限差分法的广义传输矩阵的研究

文章研究了基于时域有限差分法的时域广义传输矩阵方法,时域广义传输矩阵在包含散射体的惠更斯等效面上计算和提取,通过时域积分方程和时域有限差分法的混合应用计算得出。本文同样给出了一个在等效面上RWG基函数和FDTD网格上的变换算法。基于时域有限差分法的时域广义传输矩阵方法比基于时域步进法（MOT）和积分方程的广义传输矩阵方法更加稳定。     

组合导体目标电磁特性的快速多极算法计算

用快速多极算法分析具有任意线、面、体组合的电大尺寸理想导体目标的电磁散射和辐射特性.统一采用RWG基函数对线、面、体导体上的电流进行展开;使用了新的设置基函数和未知量的方法来处理任意的线-面,面-面连接问题;并使用多层快速多极算法结合ILUT预处理算法加速求解过程.数值结果验证了本文方法的准确性和高效性.     

GPU加速混合场积分方程求解导体目标散射问题

利用图形处理单元（GPU）加速混合场积分方程（CFIE）分析导体目标电磁散射问题。较电场积分方程（EFIE）和磁场积分方程（MFIE）,CFIE消除了内谐振问题,并且具有更好的条件数。求解的数值方法为基于 RWG基函数的矩量法（MoM）。所有计算步骤均在 GPU上实现,包括：阻抗元素填充、电压向量填充、矩阵方程的共轭梯度（CG）求解、雷达散射截面（RCS）计算。在保证数值精确度的前提下获得了数十倍的速度提升。     

基于MoM-PO的各向异性阻抗面电磁散射研究

该文基于阻抗边界条件(IBC),采用矩量法-物理光学(MoM-PO)混合算法,研究了3维各向异性阻抗面的电磁散射特性。根据表面等效原理,将空间散射场等效为MoM区和PO区电磁流的辐射场,感应电磁流以3维RWG (Rao-Wilton-Glisson)矢量基函数展开。以表面阻抗并矢表征电磁参数,给出典型各向异性阻抗面目标的电磁仿真算例,结果与Mie级数等精确解吻合良好,显示了该方法的有效性。     

复杂金属载体上线天线的MoM分析

各类金属载体上线天线的特性分析具有很重要的实用价值。本文运用矩量法处理各种载体上线天线问题。首先将线天线模拟为带状线,天线和载体表面均采用平面三角形单元进行剖分,RWG基函数作电流展开函数。然后介绍了线面连接处贴片单元的剖分方法,以及在连接处定义基函数和添加电压源模型。本文分析了各种形状金属载体上线天线的特性,研究了角度和位置对天线输入阻抗或辐射特性的影响。数值结果验证了方法的正确性。     

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。     

Linear-Linear Basis Functions for MLFMA Solutions of Magnetic-Field and Combined-Field Integral Equations

We present the linear-linear (LL) basis functions to improve the accuracy of the magnetic-field integral equation (MFIE) and the combined-field integral equation (CFIE) for three-dimensional electromagnetic scattering problems involving closed conductors. We consider the solutions of relatively large scattering problems by employing the multilevel fast multipole algorithm. Accuracy problems of MFIE and CFIE arising from their implementations with the conventional Rao-Wilton-Glisson (RWG) basis functions can be mitigated by using the LL functions for discretization. This is achieved without increasing the computational requirements and with only minor modifications in the existing codes based on the RWG functions     

Novel monopolar MFIE MoM-discretization for the scattering analysis of small objects

We present a novel method of moments (MoM)-magnetic field integral equation (MFIE) discretization that performs closely to the MoM-EFIE in the electromagnetic analysis of moderately small objects. This new MoM-MFIE discretization makes use of a new set of basis functions that we name monopolar Rao-Wilton-Glisson (RWG) and are derived from the RWG basis functions. We show for a wide variety of small objects -curved and sharp-edged-that the new monopolar MoM-MFIE formulation outperforms the conventional MoM-MFIE with RWG basis functions.     

Contamination of the Accuracy of the Combined-Field Integral Equation With the Discretization Error of the Magnetic-Field Integral Equation

We investigate the accuracy of the combined-field integral equation (CFIE) discretized with the Rao-Wilton-Glisson (RWG) basis functions for the solution of scattering and radiation problems involving three-dimensional conducting objects. Such a low-order discretization with the RWG functions renders the two components of CFIE, i.e., the electric-field integral equation (EFIE) and the magnetic-field integral equation (MFIE), incompatible, mainly because of the excessive discretization error of MFIE. Solutions obtained with CFIE are contaminated with the MFIE inaccuracy, and CFIE is also incompatible with EFIE and MFIE. We show that, in an iterative solution, the minimization of the residual error for CFIE involves a breakpoint, where a further reduction of the residual error does not improve the solution in terms of compatibility with EFIE, which provides a more accurate reference solution. This breakpoint corresponds to the last useful iteration, where the accuracy of CFIE is saturated and a further reduction of the residual error is practically unnecessary.     

Analysis of scattering by a large array of waveguide-fed wide-slot millimeter wave antennas using precorrected-FFT algorithm

An effective numerical technique employing the precorrected-fast Fourier transform (P-FFT) technique based on the method-of-moments (MoM) is presented to study the scattering from wide-slot antennas fed by waveguides with arbitrary terminations. As the Rao-Wilton-Glisson (RWG) functions are used as the basis and testing functions, the magnetic currents with arbitrary slot directions are considered. In addition, the P-FFT technique is employed to accelerate the MoM procedure for a large slot array. The numerical results are obtained and compared with both the traditional MoM results obtained using the entire-domain basis functions and the experiments results, to demonstrate better effectiveness and accuracy of this technique for millimeter wave scattering from arbitrary wide-slot antennas.     

Studies on Fast Algorithm for the Scattering of a Large Array of Waveguide-Fed Wide-Slot Antennas in Millimeter Wave Region

We present an effective numerical technique to characterize the scattering of wide-slot antennas fed by waveguides with arbitrary terminations in terms of the method of moment (MoM) and the mixed potential integral equation (MPIE). In particular, the precorrected-fast Fourier transform (P-FFT) eliminates the need to generate and store the usual square impedance matrix andthus leads to speed up the matrix-vector multiplication in the resultant system. This property makes the Rao-Wilton-Glisson (RWG) functions to be useful in simulating electrically large-scale problems. In addition, the scattering from the finite ground surfaces is accounted for in the total scattered field by using the method of equivalent edge currents. The numerical results are presented and compared with both the traditional method of moment results obtained using the entire-domain basis functions and the experimental results, to demonstrate the proposed method to be a good candidate for study on the scattering of arbitrary wide-slot large array.     

Calculation of CFIE impedance matrix elements with RWG and n/spl times/RWG functions

The method of moments (MoM) solution of combined field integral equation (CFIE) for electromagnetic scattering problems requires calculation of singular double surface integrals. When Galerkin's method with triangular vector basis functions, Rao-Wilton-Glisson functions, and the CFIE are applied to solve electromagnetic scattering by a dielectric object, both RWG and n/spl times/RWG functions (n is normal unit vector) should be considered as testing functions. Robust and accurate methods based on the singularity extraction technique are presented to evaluate the impedance matrix elements of the CFIE with these basis and test functions. In computing the impedance matrix elements, including the gradient of the Green's function, we can avoid the logarithmic singularity on the outer testing integral by modifying the integrand. In the developed method, all singularities are extracted and calculated in closed form and numerical integration is applied only for regular functions. In addition, we present compact iterative formulas for computing the extracted terms in closed form. By these formulas, we can extract any number of terms from the singular kernels of CFIE formulations with RWG and n/spl times/RWG functions.     

An accurate scheme for the solution of the time-domain Integral equations of electromagnetics using higher order vector bases and bandlimited extrapolation

Despite the numerous advances made in increasing the computational efficiency of time-domain integral equation (TDIE)-based solvers, the stability and accuracy of TDIE solvers remain problematic. This paper introduces a new numerical method for the accurate solution of TDIEs for scattering from arbitrary perfectly conducting surfaces. The work described in this paper uses the higher order divergence-conforming basis functions of Graglia et al. for spatial discretization and bandlimited interpolation functions for the temporal discretization of the relevant integral equations. Since the basis functions used for the temporal representation are noncausal, an extrapolation scheme is employed to recover the ability to solve the problem by marching on in time. Numerical results demonstrate that the proposed method is stable and that it exhibits superlinear convergence with regard to the spatial discretization and exponential convergence with respect to the temporal discretization.     

The use of curl-conforming basis functions for the magnetic-field integral equation

Divergence-conforming Rao-Wilton-Glisson (RWG) functions are commonly used in integral-equation formulations to model the surface current distributions on planar triangulations. In this paper, a novel implementation of the magnetic-field integral equation (MFIE) employing the curl-conforming n~/spl times/RWG basis and testing functions is introduced for improved current modelling. Implementation details are outlined in the contexts of the method of moments, the fast multipole method, and the multilevel fast multipole algorithm. Based on the examples of electromagnetic modelling of conducting scatterers, it is demonstrated that significant improvement in the accuracy of the MFIE can be obtained by using the curl-conforming n~/spl times/RWG functions.