高低频电磁混合算法在目标高分辨特征提取中的应用

利用电磁混合算法对复杂目标进行电磁精确建模仿真,以获得真实目标较为准确的雷达高分辨像信息,对未来高分辨雷达实现目标探测与自动识别有着重要的意义.对于电大尺寸复杂目标电磁仿真计算,高频近似方法和低频数值方法各有其优势和局限性,如能结合两者的优点来解决计算中的精度和速度问题,将对建立高分辨目标特征库有着重要的帮助.本文以低频矩量法(MoM)和高频物理光学法(PO)混合为例, 提出了基于MoM-PO混合算法来精确求解电大尺寸目标的高分辨电磁散射特性,有效地提高了计算精度, 改善了计算速度, 为快速有效地解决复杂电大尺寸目标的高分辨特征提取提供了良好的途径.通过对典型目标和实际复杂目标实例的仿真计算,提取高分辨特征结果验证了该方法的有效性和实用性.     

半空间电大均匀介质目标散射分析方法

研究了半空间电大尺寸均匀介质目标散射的高频求解方法.考虑电大均匀介质目标散射特性,将半空间并矢格林函数引入物理光学近似中,结合图形电磁学(GRECO)和射线追踪方法,分别对半空间复杂目标的消隐和多重散射进行考虑,快速有效地计算了半空间电大均匀介质目标的雷达散射截面(RCS),数值结果证明了该方法的准确性.     

三维电大目标散射求解的多层快速多极子方法

为进一步提高对电大尺寸目标散射求解的能力,详细研究了多层快速多极子方法.重点设计了用于多层快速多极子方法的各种优化方法包括Morton编号、转移因子修正内插技术与外向波重复存储策略.对于未知量数目为N的三维电磁散射,数值实验显示多层快速多极子方法具有O(NlogN)量级的计算量、O(N)量级的存储量,特别适合求解三维电大尺寸目标的电磁散射.利用该方法在单机(内存1Gb)上成功计算了未知量为25万的电大尺寸目标散射.     

用于分析电磁散射问题的快速多极算法

介绍了用于分析电磁散射问题的快速多极算法(FMA)和多层快速多极算法(MLFMA)的基本思想与基本步骤。通过计算实例表明,快速多极算法在计算速度和存贮要求方面比矩量法有明显优势,适合于在现有计算机条件下求解电大尺寸目标的散射问题。     

含腔电大目标宽角RCS的快速插值计算

提出了一种将切比雪夫逼近与弹跳射线(SBR)相结合的插值方法,并将其应用于含腔电大目标RCS宽角响应的计算中.通过SBR算法求解给定角域内切比雪夫节点处的RCS值,实现角域内任意角度入射情况下的RCS值预测,从而快速有效地分析了目标的RCS宽角响应.数值结果证明了该方法的准确性和高效性,缩短了60%以上的计算时间.     

基于改进物理光学法的电大目标双站RCS的预估

研究了电大尺寸目标双站电磁散射的改进物理光学法。针对以往双站高频算法由于忽略阴影区电流影响,导致大双站角下计算误差有所增大的问题,提取电流步进法中的迭代算子,考虑阴影区不同面元的耦合影响,与图形电磁计算方法相结合,推导出了改进的物理光学公式。分别提取照明区和阴影区面元,按照入射波方向进行排序迭代求解,快速有效地计算了电大目标的双站雷达散射截面(RCS)。通过与多层快速多极子,以及高低频混合方法进行对比,验证了该方法的有效性和准确性。     

介质目标电磁散射特性的多层特征基函数法分析

特征基函数法是近几年提出的一种基于分块和高阶基函数概念求解电磁散射问题的快速算法.为了更有效地分析电大尺寸多目标的电磁散射问题,将基于Foldy-Lax多径散射方程的特征基函数法扩展为多层特征基函数法,通过对子域进行多层划分来控制生成矩阵维数的大小和计算精度.应用多层特征基函数法计算了介质目标的远区散射场,数值结果与传统特征基函数法的计算结果吻合良好,且计算效率明显提高.     

基于高低频混合方法的梅利逼近扫频技术

将矩量法(MoM)和物理光学(PO)混合方法与梅利逼近结合分析了电大载体平台上天线的宽带辐射特性.在切比雪夫逼近的基础上,通过梅利展开技术实现快速扫频,并利用MoMPO方法减少矩阵方程中未知量个数,从而大大降低了内存需求和计算时间.相比于切比雪夫逼近,由于梅利展开式为有理函数,提高了计算精度.数值结果表明：该方法可以快速有效地分析大型载体平台上天线的宽带特性.     

介质涂敷电大尺寸导体柱电磁散射特性的有限元-快速多极混合算法分析

采用有限元-快速多极混合算法分析了介质涂层电大尺寸导体柱的电磁散射特性。与有限元-矩量法相比,快速多极算法将计算复杂度从Ｏ(N2)降低到O(N1.5),大大加快计算速度,减少存储量。计算表明该混合算法对电大复杂涂敷目标电磁特性的分析是灵活而有效的。     

基于.NET Remoting分布式计算电大目标瞬态散射特性

电磁场时域积分方程方法(TDIE)在解决瞬态电磁问题和宽带电磁问题等方面显示出独特的优势,然而TDIE的数值计算方法--时间步进算法(MOT)的计算规模较大,严重阻碍了TDIE方法在求解电大目标瞬态电磁特性中的应用.文章在研究MOT并行算法的基础上,开发了基于.NET Remoting的电磁场分布式数值计算方案.数值结果表明,该分布式并行方案显著提高了TDIE的计算效率,为解决电大目标瞬态电磁散射问题提供了一条有效途径.     

A fast MoM calculation technique using sinusoidal basis and testing functions for a wire on a dielectric substrate and its application to meander loop and grid array antennas

The input impedance matrix element of the method of moments (MoM) for an arbitrarily shaped wire antenna printed on a dielectric material Z/sub m,n/ is formulated to be composed of three terms Z/sup /spl psi/s//sub m,n/, Z/sup /spl psi///sub m,n/, and /spl Delta/Z/sub m,n/ involving single-, double-, and triple-integral calculations, respectively. The MoM based on the Z/sub m,n/ formulated in this paper (new MoM) is applied to two antennas-a meander loop antenna and a grid array antenna-as well as a simple loop used as a reference antenna. The computation time to obtain the current distribution of each antenna by the new MoM technique is compared with the time required for the conventional MoM, which has an impedance matrix element composed of four terms, all involving triple-integral calculations. It is revealed that the new MoM drastically reduces the computation time: for example, by a factor of 937 for the grid array antenna. In addition, the radiation characteristics of these two antennas are discussed. It is found that a reduced-size meander loop (62% smaller than the simple loop reference) has a radiation pattern similar to the simple loop reference. It is also found that the grid array has an axial beam radiation pattern without side lobes in the principal planes.     

电大尺寸物体电磁辐射与散射特性几种分析方法的比较研究

在一定的规则剖分下，矩量法中的系数矩阵为Ｔｏｅｐｌｉｔｚ矩阵或多重Ｔｏｅｐｌｉｔｚ矩阵。利用这一特征而提出的共轭梯度（ＣＧＭ）和快速付里叶变换（ＦＦＴ）算法已成为目前国际上分析电大尺寸问题的一种有效手段。虽然ＣＧＭ—ＦＦＴ将普通矩量法中正比于Ｎ２（Ｎ为系数矩阵的阶数）的存储量压缩为正比于Ｎ的存储量，但其迭代算法使所花ＣＰＵ时间仍与普通矩量法相当。本文采用基于递推的Ｌｉｖｅｎｓｏｎ算法和一种库软件处理同样的问题，所花ＣＰＵ时间和普通矩量法相比降低两个量级，而且存储量比ＣＧＭ—ＦＦＴ技术还要小。本文以直导线的辐射和散射问题为例介绍了几种算法的基本原理，并对他们的计算时间和存储空间等进行了比较研究，得出了一些重要结论。     

基于特征基函数法的一维理想导体粗糙海面电磁散射快速算法研究

针对传统矩量法在处理具有较多未知量的理想导体粗糙海面电磁散射问题时对计算机内存的需求过大, 耗时过长的缺陷, 文中引入了特征基函数法, 并根据Foldy-Lax多径散射方程构造特征基函数, 首先只考虑离散子域本身的自相互作用构造主要特征基函数, 然后考虑各离散子域间的互耦效应构造次要特征基函数, 最后由主要特征基函数和次要特征基函数的加权叠加构造特征基函数.通过与传统矩量法仿真结果的对比, 讨论了不同次要特征基函数的阶数或不同离散子域的个数对计算精度和计算效率的影响.仿真结果表明了本文所采用的算法能够在保证计算精度的前提下, 减少计算时间, 并能够通过离散子域尺寸的选取控制实际操作矩阵的维数.     

基于超级计算机的矩量法性能分析与优化

复杂目标的精确电磁特性分析往往需要巨大的存储和极长的计算时间。针对这一问题,结合国内发展迅速的超级计算机系统,研究了具有精确高效仿真能力的高性能电磁算法——高阶矩量法。提出了单元预选法来消除矩阵并行填充过程中的无效计算,加速矩阵填充过程。提出了一种具有更少的通信次数和通信量的新型并行LU分解算法,加速矩阵方程求解过程。数值测试表明提出的矩阵并行填充算法和矩阵方程并行求解算法在超级计算机平台上都能获得较高的并行性能,大幅提高了矩量法的仿真能力。     

PC群集系统中并行矩量法研究

目前复杂环境的EMC分析,计算量过大,耗时太长,使分析与优化遇到实质性的困难.本文研究MPI结合矩量法的并行技术,测试了在PC群集系统中并行矩量法的性能,并以此完成大型计算.与大型机和工作站相比,PC群集系统中的并行矩量法可以用较低的硬件成本有效的实现复杂环境电磁特性分析.     

A new lateral PNM Schottky collector bipolar transistor (SCBT) onSOI for nonsaturating VLSI logic design

The novel characteristics of a new lateral PNM Schottky collector bipolar transistor (SCBT) on silicon-on-insulator (SOI) are explored using two-dimensional (2D) simulation. The collector-base junction of the proposed lateral PNM transistor consists of a Schottky junction between n-base (N) and metal (M). The characteristics of this structure are compared with that of lateral PNP transistors on SOI. We demonstrate that the proposed structure has a superior performance in terms of reduced collector resistance, high current gain, negligible base widening, and very low reverse recovery time compared to the compatible lateral PNP transistors. A simple fabrication procedure is also suggested providing the incentive for experimental verification     

Genetic algorithms and method of moments (GA/MOM) for the design ofintegrated antennas

This paper introduces a novel technique for efficiently combining genetic algorithms (GAs) with method of moments (MoM) for integrated antenna design and explores a two example applications of the GA/MoM approach. Integral to efficient GA/MoM integration is the use of direct Z-matrix manipulation (DMM). In DMM a “mother” structure is selected and its corresponding impedance or Z-matrix is filled only once prior to beginning the GA optimization process. The GA optimizer then optimizes the design by creating substructures of the mother structure as represented by the corresponding subsets of the original mother Z-matrix. Application of DMM with GA/MoM significantly reduces the total optimization time by eliminating multiple Z-matrix fill operations. DMM also facilitates the use of matrix partitioning and presolving to further reduce the optimization time in many practical cases. The design of a broad-band patch antenna with greater than 20% bandwidth and a dual-band patch antenna are presented as examples of the utility of GA/MoM with DMM. Measured results for the dual-band antenna are compared to numerical results. Excellent agreement between numerical and measured results is observed     

Higher order hybrid method of moments-physical optics modeling technique for radiation and scattering from large perfectly conducting surfaces

An efficient and accurate higher order, large-domain hybrid computational technique based on the method of moments (MoM) and physical optics (PO) is proposed for analysis of large antennas and scatterers composed of perfectly conducting surfaces of arbitrary shapes. The technique utilizes large generalized curvilinear quadrilaterals of arbitrary geometrical orders in both the MoM and PO regions. It employs higher order divergence-conforming hierarchical polynomial basis functions in the context of the Galerkin method in the MoM region and higher order divergence-conforming interpolatory Chebyshev-type polynomial basis functions in conjunction with a point-matching method in the PO region. The results obtained by the higher order MoM-PO are validated against the results of the full MoM analysis in three characteristic realistic examples. The truly higher order and large-domain nature of the technique in both MoM and PO regions enables a very substantial reduction in the number of unknowns and increase in accuracy and efficiency when compared to the low-order, small-domain MoM-PO solutions. The PO part of the proposed technique, on the other hand, allows for a dramatic reduction in the computation time and memory with respect to the pure MoM higher order technique, which greatly extends the practicality of the higher order MoM with a smooth transition between low- and high-frequency applications.     

一种有效的吸收边界条件及其在散射问题中的应用

本文推导了非均匀各向异性媒质的有限差分方程,通过改变参数可以使该差分方程适用于均匀、非均匀、各向同性或各向异性等各种情况下柱体的散射计算.文中还给出了一种新的吸收边界条件,并与不变性测试方程法和矩量法在计算时间、存贮空间方面进行了比较.结果表明:运用这个条件在计算时间和存贮空间上都具有优点,是计算电大尺寸媒质柱体电磁散射特性的一种有效手段.     

Hybrid Use of AWE With Spatial Matrix Interpolation in the Analysis of Printed Structures

In the asymptotic waveform evaluation (AWE) method, most of the CPU time is spent in the generation of the method of moment (MoM) matrix and its derivatives. In this letter, the hybrid use of the AWE method with the spatial interpolation of the MoM matrix is introduced to reduce the matrix generation time. The numerical results demonstrate the efficiency and the accuracy of the proposed technique.