64位计算技术求解电大尺寸电磁计算问题

研究了64位计算技术求解电大尺寸电磁计算问题的能力。基于矩量法（MOM）的基本原理,利用C语言开发32位矩量法计算程序,给出算例验证程序的有效性。分析32位系统对程序的限制发现,对于电大尺寸问题,当内存需求大于2.2 GB时,32位程序无法计算。利用64位编程技术,开发了64位矩量法的计算程序。对比表明,64位技术能明显提高矩量法的计算范围,增强了矩量法求解电大尺寸电磁计算问题的能力。64位计算技术,提供了矩量法求解电大尺寸目标的另一种途径。     

深腾1800系统MPI并行矩量法分析线天线

针对目前用矩量法分析电大尺寸物体的辐射和散射时,计算量过大,耗时太长,使分析与优化遇到实质性的困难。研究MPI结合矩量法的并行技术,用并行雅可比迭代法求解矩量法矩阵方程的并行实现过程,测试了其在深腾1800系统中并行矩量法的性能。     

渐近波形估计技术在三维电磁散射问题快速分析中的应用

本文将渐近波形估计技术应用到矩量法中,计算了三维理想导体目标的宽带雷达散射截面(RCS)和单站RCS方向图.用矩量法求解电场积分方程,得到给定频率点、给定方向入射波照射下的导体表面电流密度,应用渐近波形估计技术分别得到频带内任意频率点以及任意角度入射波照射下的导体表面电流密度,进而计算出宽带RCS和单站RCS方向图.计算结果表明渐近波形估计技术与矩量法结合可以逼近矩量法逐点计算的结果,且计算效率大大提高.     

复杂电磁环境中线天线近场数模预测

本文应用矩量法和几何绕射理论的混合技术及矩量法的稀疏技术详细分析和计算了多导体同时存在的复杂电磁环境中线天线的近场，理论值与实验数据进行比较，两者基本吻合。     

并行核外高阶矩量法分析机载天线受扰特性

利用核外算法,将计算机硬盘动态的纳入矩量法求解过程打破内存的限制,同时采用并行计算技术加速矩量法的求解过程。通过某飞机的双站雷达散射截面(RCS)计算,验证了核外算法的正确性。最后,将并行核外高阶矩量法用于机载伞形印刷振子天线阵列辐射特性分析,结果表明,该方法可充分利用计算机的硬盘,扩大矩量法可求解问题的规模。     

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.     

解决电大尺寸电磁场问题的改进矩量法研究

首先介绍基于积分方程的矩量法原理及其特点.基于传统矩量法在解决电大尺寸电磁场问题上的局限性,分析几种典型的改进矩量法,包括快速多极子方法、小波矩量法、混合算法和自适应积分法.几种方法通过不同的途径减小了计算量,所以将几种方法结合起来使用,可以有效地解决电大尺寸电磁场问题.运用改进的矩量法,突破了传统矩量法解决电大尺寸电磁场问题的局限性.     

电磁问题的改进型矩量法

本文提出了一种新型的矩量法求解技术－改进型矩量法。在对电磁问题的数值分析中，这一方法提供了一个有别于矩量法的新思路，也提供了一个减少所使用计算机内存和缩短计算时间的新途径，用这一理论方法计算了若干天线实例。其计算结果与已知公开发表的结果相比较，或与所加工硬件的实测结果相比较，一致性良好。     

任意截面波导的小波矩量法分析

用离散小波矩量法推导出了任意截面波导的特征值方程,并以常见规则波导为例,对其截止波数进行数值计算,所得结果与理论值吻合良好,从而使小波矩量法求解波导问题的可行性和有效性得以验证;文中分别用矩量法和小波矩量法对矩形波导主模的截止波长进行计算,通过对比其运算时间和收敛速度,表明在保证精度的前提下,小波矩量法能有效提高运算速度。     

一种介质体宽角域散射的快速分析方法

本文结合渐近波形估计技术(AWE)和体积分方程矩量法(VIE-MoM)快速分析介质体的宽角域散射问题。体积分方程用来对介质目标建模,用四面体元对目标进行体剖分,采用SWG基函数模拟四面体元内的电通量密度。应用矩量法将体积分方程离散生成矩阵方程。目标的雷达散射截面(RCS)高度依赖入射波方向,应用渐近波形估计技术在给定角度对电通量密度进行泰勒展开,采用padé逼近进一步展宽角域范围。最后,数值算例表明渐近波形估计技术结合体积分方程矩量法在介质宽角域散射分析方面的准确性和高效性。     

机载天线辐射方向图的MoM-UTD混合法分析

采用矩量法(MoM)结合一致性几何绕射理论(UTD)的混合方法分析了机载单极天线的辐射特性。用该混合方法建立的机载天线辐射模型更符合实际,并且它同时具有MoM的精确性和UTD的高效性,克服了单一方法的不足。计算结果对于预测天线间的电磁兼容性和优化天线布局具有一定的指导意义。     

A hybrid technique for combining the moment method treatment of wire antennas with the GTD for curved surfaces

This hybrid technique is a method for solving electromagnetic problems in which an antenna is located near a conducting body. The technique accomplishes this by casting the antenna structure in a moment method (MM) format, then modifying that format to account for the effects of the conducting body via the geometrical theory of diffraction (GTD). The technique extends the moment method to handle problems that cannot be solved by GTD or the moment method alone. Wire antennas are analyzed to find their input impedance when they are located near perfectly conducting circular cylinders, although the methods used are not restricted to circular cylinders. Three orthogonal orientations are identified, and antennas to match them are analyzed. For each case, the hybrid solution is checked with one of three independent solutions: an MM-eigenfunction solution, image theory, or experimental measurement. In almost all cases, excellent agreement is obtained due in large part to the fact that the moment method near fields are, for the first time, cast into a ray optical form.     

A Two-Level Preconditioning Technique for Wire Antennas Attached with Dielectric Objects

An iterative solution of linear systems is studied,which arises from the discretization of a wire antennas attached with dielectric objects by the hybrid finite-element method and the method of moment (hybrid FEM-MoM).It is efficient to model such electromagnetic problems by hybrid FEM-MoM,since it takes both the advantages of FEM's and MoM's ability.But the resulted linear systems are complicated,and it is hard to be solved by Krylov subspace methods alone,so a two-level preconditioning technique will be studied and applied to accelerate the convergence rate of the Krylov subspace methods.Numerical results show the effectiveness of the proposed two-level preconditioning technique.     

Efficient EMC Simulation of enclosures with apertures residing in an electrically large platform using the MM-UTD method

The moment method coupled with the uniform theory of diffraction is employed in this paper to simulate the electromagnetic shielding performance of an enclosure with apertures residing in a very large platform, in which the moment method is used to accurately model the enclosure with apertures, and the influence of the large platform is efficiently calculated by using the uniform theory of diffraction. These two methods are coupled through the tangential electromagnetic fields on the apertures of the enclosure. In this paper, the accuracy of this coupled method developed is validated, and we apply this method for simulating the shielding effectiveness with the sources inside/outside the enclosure. The simulation results show that this coupled technique is able to simultaneously model the effects of the smaller structures and the large platform on the total electromagnetic property. It further demonstrates that this coupled method is a very flexible and powerful technique for analysis of the electromagnetic compatibility problems with smaller objects mounted on a larger platform.     

Rapidly converging spectral-domain analysis of rectangularly shielded layered microstrip lines

A moment-method-oriented direct integral-equation technique is presented for the exact analysis of rectangularly shielded layered microstrip lines. This technique retains the simplicity of conventional moment methods while optimizing them by recasting all matrix elements into rapidly converging series. Filling up the matrix requires no numerical integration. The proposed algorithms yield highly accurate results both for the modal currents and propagation constants.     

机载天线辐射方向图的MM—UTD混合法分析

采用矩量法（MM）结合二致性几何绕射理论（UTD）的混合方法计算了机载单极天线的辐射方向图。该混合方法建立的机载天线辐射模型更符合实际，并且它同时具有MM的精确性和UTD的高效率，克服了单一方法的不足。计算结果对于预测天线间的电磁兼容性和优化天线布局具有一定的指导意义。     

Nonparametric estimation of mean Doppler and spectral width

This paper proposes a new nonparametric method for estimation of spectral moments of a zero-mean Gaussian process immersed in additive white Gaussian noise. Although the technique is valid for any order moment, particular attention is given to the mean Doppler (first moment) and to the spectral width (square root of the centered second spectral moment). By assuming that the power spectral density (PSD) of the underlying process is bandlimited, the maximum-likelihood estimates of its spectral moments are derived. A suboptimal estimate based on the sample covariance is also studied. Both methods are robust in the sense that they do not rely on any assumption concerning the PSD (besides being bandlimited). Under weak conditions, the set of estimates based on sample covariance is unbiased and strongly consistent. Compared with the classical pulse pair and the periodogram-based estimators, the proposed methods exhibit better statistical properties for asymmetric spectra and/or spectra with large spectral widths, while involving a computational burden of the same order     

Numerical Solution of Coupling Between Two Collinear Parallel-Plate Waveguides

The problem of coupling between two collinear parallel-plate waveguides is investigated numerically using moment methods. The exciting mode in the waveguide is assumed as the incident field, and the integral equation for the induced current is expressed in terms of the reflected, transmitted, and evanescent currents on the waveguides. The integral equation is then solved numerically by a point-matching method and the reflection and the transmission coefficients and the radiated fields are obtained. To examine the accuracy of the results, the special case of a semi-infinite exciting waveguide coupled to a finite coupled waveguide is also considered and is solved numerically by treating the singularities of the induced currents using a transformation method. For a TE/sub 0,1/ excitation of the exciting waveguide, the results of both numerical methods are compared with the analytical results obtained previously using the Wiener-Hopf technique, and are found to be in good agreement. The methods are then used to study the effect of the coupled waveguide on the radiation field.     

Improved moment preserving block truncation coding for image compression

A novel image compression scheme based on moment preserving block truncation coding (MPBTC) is introduced. To reduce the bit rate of the traditional MPBTC scheme, the block search order coding technique is employed to exploit the similarity among neighbouring image blocks. In addition, smooth blocks and complex blocks are processed using different methods. Experimental results show that the proposed scheme provides good image quality at a low bit rate.     

IPO-MoM混合法分析开槽电大目标的电磁散射

本文利用迭代物理光学法（ＩＰＯ）与数值方法相结合的混合方法计算二维开槽民大目标的电磁散射,首先根据等效原理将散射场进行分解,分别采用ＩＰＯ法和矩量法（ＭｏＭ）计算槽缝填充的电大目标和槽缝的散射,并在口径处应用广义网络原理处理耦合问题,数据结果表明本文方法是准确和高效的。