介质涂敷电大腔体电磁散射IPO研究

将迭代物理光学法(IPO)推广应用于研究具有非完纯导电边界的电磁散射问题,建立了相应的理论模型,并应用到内壁涂敷介质的电大尺寸腔体的电磁散射特性分析中。在每一次IPO迭代步骤中,应用Fresnel反射系数计算出介质表面总场。通过多次迭代,求出腔体内壁上稳定的电磁场分布,进而计算出腔体的电磁散射特性。数值结果表明了这种扩展的IPO方法的在分析电大尺寸介质涂敷目标中的正确性和高效性。     

电大尺寸复杂结构腔体电磁散射的IPO/FEM混合法研究

该文将物理光学迭代法（IPO）的子域连接法与矢量有限元法（FEM）相结合，提出了一种新的混合方法用于分析计算电大尺寸复杂结构腔体目标的电磁散射特性，对于腔体内部适合用高频方法处理的部分采用IPO方法分析；对于具有复杂结构和材料特性的部分，采用矢量有限元法进行研究，利用交界面上的连续性条件实现这两种方法的耦合，为了验证理论模型的正确性，该文对某一矩形空腔及底部加载金属台阶的腔体进行了分析，计算结果与文献数据以及用时域有限差分法所得结果一致，并具有很好的收敛效果。在此基础上，对底部加载介质层的复杂结构腔体进行了分析计算，结果表明这种混保方法对于分析电大尺寸复杂结构腔体的散射特性是行之有效的。     

电大尺寸开口腔体电磁散射特性的DDM/FEM-BIE混合法分析

该文将超松弛重叠及非重叠区域分裂法(DDM)与矢量有限元方法(EB-FEM)、边界积分方程(BIE)法相结合对三维电大尺寸开口腔体的电磁(EM)散射特性进行分析。通过DDM将原腔体分解成若干子腔体,在各子腔体内应用EB-FEM进行分析。腔体间应用矢量传输条件进行耦合,最终腔体内电场分布通过迭代获得。在原腔体口面,运用积分方程进行描述.在分析过程中,将传输条件和BIE统一成第三类边界条件形式。最后给出的数值结果验证了DDM/FEM-BIE混合方法分析腔体的电磁散射特性的精确性及高效性。     

IPO+FMM混合方法结合GRI和级联技术计算电大腔体的RCS

采用快速方法(FMM,RPFMM,FaFFA)加速迭代物理光学法(IPO)的迭代过程,可以快速计算电大腔体的电磁散射特性.采用广义互易积分,用靠近腔体终端的一个St面将腔体分成两段,形状简单光滑的腔体前端用IPO结合快速算法处理,而腔体终端单独分析.为了能够处理深腔体和进一步加快计算速度,将腔体前端进一步分成几个子腔体,每一个子腔体独立分析,通过一个级联方法求得腔体前端在St面产生的辐射场,最终在St面用广义互易积分求得腔体的RCS.数值计算结果表明该方法是准确的,同时能有效地提高计算速度.     

FMM用于快速计算电大腔体的RCS

利用迭代物理光学法(IPO)计算一般电大尺寸腔体的电磁散射特性,在迭代过程中用快速多极子方法(FMM)加速计算.在雅可比最小残差法(JMRES)的积分运算中引入FMM并与共扼梯度法(CG)的计算效率进行了比较.采用结构化分组,利用转移因子的平移不变性对计算和存储进行了优化.计算结果表明这些加速方法是有效的并能极大地提高计算效率.     

介质涂覆电大复杂腔体散射的快速求解

利用腔体涂覆层是薄层损耗介质的情况,引入阻抗边界条件求解腔体的介质涂覆区域.详细推导了快速多极子方法结合迭代物理光学法和阻抗边界条件的混合计算公式.在此基础上利用前后向迭代方法加速收敛.计算结果表明该方法比IPO FMM方法有效地减少了迭代次数,能够对腔体涂覆材料的电磁参数、腔体涂覆部位进行优化设计,对开口腔体的RCS减缩提供理论参考.     

应用谱域迭代算法计算理想导电腔体的RCS

本文介绍了利用谱域迭代方法计算理想导电腔体后向散射和RCS的方法,揭示了波谱在腔体内传播的过程。针对腔体截面形状的不同,给出了应用等效电磁流法解决腔体边缘绕射对口径场影响的方法。最后通过算例验证了方法的正确性。     

基于DDM技术的FEM/PO-PTD方法在深腔导体目标RCS分析中的应用

采用一种基于区域分解法(DDM)的混合方法——FEM/PO—PTD法，分析带有深腔的三维电大尺寸导体目标的电磁散射特性。应用DDM将原有深腔分成若干个较小的子域。对于腔体开口面所在子域，应用等效原理，结合物理光学法(PO)与物理绕射理论(PTD)，得到腔体开口面的边界积分方程；对于其它子域，通过传输条件实现各子域间的耦合。在各子域内推导出此边值问题的等价泛函。应用基于棱边的有限元法(Edge—based FEM)进行分析。理论分析与计算结果表明，该混合方法与其它计算同类问题的方法相比，有较高的计算精度，同时能减少对计算机内存的需求     

电大尺寸开口腔体电磁散射的子结构法研究

将子结构法与矢量有限元法相结合对无限大接地的三维开口腔体的电磁散射特性进行分析.将原尺寸较大的腔体分解成若干个不重叠的子腔体,在各子腔体内应用矢量有限元法进行分析,在原腔体开口面应用边界积分方程描述.通过求解容量矩阵获得子腔体之间连接边界上的场值,可以快速获得腔体开口面上的场值,极大地减少了存储量和计算量,易于对电大尺寸腔体的电磁散射问题进行分析.数值算例验证了该方法的准确性和高效性.     

带有腔体或槽缝的电大尺寸目标电磁散射特性分析

本文提出了一种新的混合方法—FEM/PO-PTD法,应用于分析计算带有腔体或槽缝的电大尺寸复杂目标电磁散射问题.在该方法中,采用基于棱边的有限元法(edge-based FEM)为低频方法,物理光学法(PO)与物理绕射理论(PTD)为高频方法,通过耦合技术将两者结合在一起.为了验证该方法的准确性,本文首先将其应用于三维无穷接地开口腔体的电磁散射特性分析,计算结果与有关文献的数据一致性很好.在此基础上,给出了几种不同介质填充的三维开口腔体和带有槽缝的三维有限尺寸导体柱雷达散射截面的计算曲线,对分析有关工程问题有指导意义.理论分析与计算结果表明,本文提出的混合方法与其它计算同类问题的方法相比,能节省计算机存储单元、提高计算速度.     

快速分析电大腔体电磁散射的混合算法

为提高电大腔体电磁散射分析的效率,提出将迭代物理光学法（IPO）与快速多极子方法（FMM）相结合的混合算法IPO＋FMM,给出该混合算法的数学模型推导,该算法可将每迭代步的计算量由O（N^2）降到O（N^1.5）,最后分析了二种不同形状的电大尺寸腔体的雷达散射截面。数值结果表明,该混合算法与IPO算法相校,精度相当但效率有显著提高。     

矩形涂层板的电磁散射

本文讨论了涂覆有耗介质的矩形平板的电磁散射。涂层介质的参数可以任意。表达式中涉及的Maliuzhinets函数的计算,由于采用了多项式近似,避免了复平面内的积分,从而使计算时间大为减少。最后将理论计算结果与实验值相比较,两者吻合得很好。     

Sequential and parallel implementations of the partitioningfinite-element method

With the computational capabilities of parallel computers, we should investigate new methods which have performance advantages on parallel computers even if they are not faster than conventional methods on sequential computers. One such method is the partitioning finite-element method (FEM). In this paper, we consider the implementation of the partitioning FEM on both the Gray Y-MP and the Intel Touchstone Delta. The partitioning method is shown to have many advantages over a traditional finite-element approach. On the Gray YMP and sequential computers, the partitioning method requires significantly less memory. For parallel processors such as the Intel Delta, we show that the partitioning FEM has a higher parallel efficiency than traditional FEM. EM scattering from an infinitely long dielectric cylinder is used as an example     

Scattering from an infinite conducting cylinder covered with afinite two-layer dielectric coating (modal approach)

The electromagnetic scattering problem of a conducting infinite circular cylinder partially shielded with a finite two-layer dielectric coating has been analyzed. Cylindrical eigenfunctions with unknown modal coefficients are used to expand the interior EM fields in terms of Fourier-Bessel series. Enforcing field boundary conditions at the dielectric-dielectric interface leads to a single set of modal coefficients for field expansions inside the inner and the outer dielectric layers. Replacing the dielectric coating with the induced polarization sources and utilizing pertinent Green's functions, the dielectric-scattered fields are then formulated in terms of the modal coefficients. Imposing field equivalence conditions yields sets of linear algebraic equations for numerical computation of the unknown modal coefficients and subsequently other parameters of interest. Computed backscattered fields based on the modal technique developed are compared to experimental and numerical data obtained for the 2-D problem of a dielectric coated conducting cylinder     

左手材料电磁散射特性的仿真研究

分别采用电磁场仿真软件CST MWS和CADFEK0仿真计算了不同电尺寸右手材料和左手材料介质球的电磁散射特性,并对电磁散射数值进行分析,同时与Mie理论计算结果相比较,可得出以下结论:无论在仿真电小尺寸还是电大尺寸的目标时,CADFEK0仿真效果部比CST MWS更佳.最后用CADFEKO软件仿真了金属球涂覆右手材料...     

Radiation characteristics of cavity backed aperture antennas infinite ground plane using the hybrid FEM/MoM technique and geometricaltheory of diffraction

A technique using the hybrid finite element method (FEM)/method of moments (MoM) and geometrical theory of diffraction (GTD) is presented to analyze the radiation characteristics of cavity fed aperture antennas in a finite ground plane. The cavity which excites the aperture is assumed to be fed by a cylindrical transmission line. The electromagnetic (EM) fields inside the cavity are obtained using finite element method (FEM). The EM fields and their normal derivatives required for FEM solution are obtained using: (1) the modal expansion in the feed region and (2) the MoM for the radiating aperture region (assuming an infinite ground plane). The finiteness of the ground plane is taken into account using GTD. The input admittance of open-ended circular, rectangular, and coaxial line radiating into free space through an infinite ground plane are computed and compared with earlier published results. Radiation characteristics of a coaxial cavity-fed circular aperture in a finite rectangular ground plane are verified with experimental results     

介质柱电磁极化散射的计算和分析

本文首次给出柱形体的一种有价值的极化散射矩阵Ｓ,定义,Ｓ,具有六个自由度,它包含了柱形体散射的所有信息,并给出计算平行极化ＲＣＳ的垂直极化ＲＣＳ等公式。从Ｓｓ也易于导出线极化基极化散射矩阵Ｓｔ和圆极化基极化散射矩阵Ｓｃ等。在此基础上本文将ＭｏＭ－ＣＧＭ－ＦＦＴ混降低了所需计算机内存和ＣＰＵ,提高了计算效率。本文以介质板柱体的极化散射为例进行了计算,所得结果与理论结果与及其它文献中的精确结果进行比较     

Scattering of electromagnetic waves by a perfectly conductingcylinder with a thin lossy magnetic coating

We study the scattering interaction of electromagnetic (EM) waves with an infinite cylinder coated with a lossy dielectric material with frequency-dependent material properties. These properties are hypothetical, yet representative of a wide class of available materials. The monostatic and bistatic scattered widths (SW) are evaluated for the TM or TE polarization cases. These calculations require the use of algorithms to evaluate Bessel-Hankel functions of complex arguments. These algorithms are based on a continued fraction approach, which ensures stability of the recursion relations. The bistatic plots of the TM and TE scattering widths for the coated body are displayed in a convenient color-graded scale. The reductions in the scattering widths produced by this type of coating are determined in selected frequency bands and angular sectors, in both polarization cases. It is quantitatively shown how curvature and polarization shift the effectiveness band of the coating. The determined regions in which the SW are minimally affected are the most suitable for target identification purposes