涂覆型大尺寸有限长圆柱散射特性的混合解法

本文首先从理论上导出了能计算斜入射绕射场的阻抗劈并矢绕射系数,然后利用该绕射系数结合物理光学法对涂覆型大尺寸有限长圆柱的散射特性进行了分析和计算。在绕射区计及了一阶和二阶绕射贡献,在镜反射方向附近作了驻相法近似,由此得到的数值结果与实验结果吻合较好。     

Radiation from a Dipole near a Conducting Cylinder of Finite Length

Antennas radiating in free space or above a reflecting plane produce radiation patterns which are in general predictable. When these same antennas are mounted on bodies such as aircraft, submarines, or satellites, secondary currents may be induced on the fuselages and nearby conducting members. These secondary currents often result in unpredictable radiation in the forms of newly introduced polarizations or unwanted lobe structures which together may manifest themselves in the form of radio-frequency interference. As a model of the fuselage of either of the aforementioned conducting bodies, a cylinder of finite length is considered and the radiation fields of a radial dipole in the immediate vicinity of such a cylinder are determined by a theoretical-numerical technique. A cross- polarized field due to axial currents induced along the cylinder is found to represent a predominant feature of the radiation characteristics of the dipole-cylinder configuration.     

Scattering by a Conducting Infinite Cylinder Illuminated with a Shaped Beam

An analytic solution to the shaped beam scattering by a conducting infinite cylindrical particle is constructed within the framework of the generalized Lorenz-Mie theory (GLMT). The expansion coefficients of the scattered electromagnetic fields are derived by using the boundary conditions. As an example, for a tightly focused Gaussian beam propagating perpendicular to the cylinder axis, the scattering characteristics that obviously demonstrate the three-dimensional nature, as with the case of a dielectric infinite cylinder, are described in detail, and numerical results of the normalized differential scattering cross section are evaluated.     

Two-Dimensional Scattering by a Conducting Elliptic Cylinder Coated With a Homogeneous Anisotropic Shell

A solution to the two-dimensional scattering properties of a conducting elliptic cylinder coated with a confocal homogeneous anisotropic elliptical shell is obtained. The transmitted field of the anisotropic shell is expressed as an integral equation based on waves with different wave numbers and different directions of propagation. The waves in all directions are represented as the eigenfunction expansion in elliptic coordinates in terms of Mathieu functions. In order to solve the nonorthogonality properties of Mathieu functions, Galerkin's method is applied and a matrix is required for the computation of unknown expansion coefficients of the scattered and transmitted fields. Only the transverse magnetic (TM) polarization is presented, while the transverse electric (TE) polarization can be obtained in the same way. Some numerical results are presented in graphical forms. The result is in agreement with that available as expected when a coated elliptic cylinder degenerates to the coated circular one.      

有耗介质覆盖导电圆柱的电磁散射

本文给出了在平面波垂直照射下，均匀覆盖有耗介质后的导电圆柱散场的本征函数级数解。     

A General Spectral-Domain Formulation of the Electromagnetic Scattering by a Perfectly Conducting Circular Cylinder

A full-wave method for the two-dimensional scattering problem by a perfectly conducting circular cylinder is presented, providing an exact solution for the Helmholtz equation in very general cases. The method is based on the Fourier series expression of the boundary conditions (Dirichlet and Neumann) generated by an arbitrary, finite-power, incident beam, and the analysis is performed in the complex plane of the analytic continuation of a space spectral variable. This approach allows us to define an analytic continuation for cylindrical wave expansions, working with lossy propagation media and with a full incident spectrum, including inhomogeneous waves, both in E and in H polarization. Convergence of the modal expansion is investigated, to verify that very weak hypotheses are needed, and no geometrical or paraxial approximation is required. Extact expressions for the expansion coefficients are given, in terms of complex intergrations involving the Fourier spectrum of the incident beam.     

Scattering of a Monopolar TE-Polarized Electromagnetic Pulse on an Ideally Conducting Cylinder

Journal of Communications Technology and Electronics - Abstract—The problem of scattering on an ideally conducting infinite cylinder of a monopolar electromagnetic pulse, the electric field...     

时域MEI方法在矩形导体柱散射问题中的应用

本文用时域有限差分法（FDTD）模拟二维矩形导体柱的电磁散射场，采用时域不变性测试方程（MEI）作为吸收边界条件对该散射场进行求解。将所得计算结果与截断边界网格点采用Mur二阶吸收边界条件所得的数值结果相比较，两者吻合很好。结果表明使用时域MEI方法作为吸收边界条件能有效缩短截断边界与物体边界的距离，且能得到足够精确的解。     

Analysis of Electromagnetic Waves Scattering by a Finite Size Dielectric and Metal Cylinder in a Rectangular Waveguide

The paper presents a rigorous solution of the scattering problem by a circular dielectric and perfectly conducting cylinders of any radius and any height in the rectangular waveguide oriented perpendicularly to a wall. The method is based on the representation of fields in waveguide and dielectric medium by cylindrical eigenfunctions and application of boundary conditions on surfaces of the cylinder to evaluate the fields inside and outside the cylinder. The reflection and transmission coefficients are expressed through the fields. As an example the reflection and transmission coefficients versus frequency for various dielectric and metallic cylinders are computed. The comparison of numerical with experimental data is presented.     

导电平面上槽与缝的散射

在雷达散射截面（ＲＣＳ）和电磁脉冲（ＥＭＰ）研究中，我们常常需要考虑目标上各个部分结合处存在的槽或缝的散射。在现代，随着ＲＣＳ减缩技术的发展，这些槽和缝对目标双站散射行为的影响已经日益突出。对此，通过等效原理导出相应问题的全波公式，研究了具有不同几何形状和不同材料填充的槽或缝对目标散射图形的影响     

An Experimental Investigation of the Distribution of Current And Charge Induced on a Tubular Conducting Cylinder by an Electromagnetic Pulse

The distribution of current and charge induced on a tubular cylinder by an electromagnetic pulse (EMP) is investigated experimentally in the Harvard parallel-plate EMP simulator (HES). The pulse shapes of the current and charge induced on the surface of the cylinder are measured. After Fourier transforms of the observed pulse shapes are taken, the distributions of the several frequency components on the surface are obtained. The measured distribution of each frequency component is then compared with the theoretical distribution calculated using Kao's method.     

电磁格点理论在有耗介质涂层导体柱TE和TM波散射中的应用

本文采用格点理论，建立了求解有耗介质涂层导体柱电磁散射（包括ＴＭ和ＴＥ两种情况）的基本方法。涂有有耗介质层的导体柱可以看成是一群由面格点和线格点组成的混合格点，分析它们的自作用和互作用，可以方便地解决散射问题。文中还给出了若干计算实例。     

任意截面导体柱的电磁散射数值解

卡门翼形和任意多边形是两种典型的不规则形体，由于其不规则曲边和尖锐的角点，它们的电磁散射问题给传统的FDTD数值求解造成了一定的困难，这是因为要获得较高的精度，必须细分网格，从而增加内存需求和计算时间，本文利用形体变换结合时域有限差分法的Thompson-FDTD方法对这两种典型的不利形体的散射问题进行了数值模拟，其结果进一步验证了Thompson-FDTD方法对散射体几何形状变化具有较强的适应能力和较高的数值精度。     

基于MEI吸收边界条件的导体柱散射问题模拟

首次在圆柱坐标系时域有限差分 (FDTD)法中采用基于时域不变性测试方程 (MEI)方法的吸收边界条件 ,对导体圆柱的电磁散射问题进行了数值模拟研究。在相同计算条件下 ,与应用Bayliss Turkel二阶辐射边界条件的FDTD结果相比较 ,直观地表明MEI方法结果与解析解吻合更好     

等离子体覆盖导体柱宽带散射特性分析

利用分段线性递归卷积频率相关时域有限差分（RLRC FD^2TD)方法研究了非均匀等离子体覆盖导体柱的散射特性，对TM波垂直入射时的双站、宽带仿真结果的分析表明，等离子体包层可以显著地减少雷达目标的电磁回波能量，衰减量与多种参数有关。     

矩阵摄动理论在二维有耗介质柱局部逆散射中的应用

本文提出二维有耗介质柱局部逆散射的矩阵摄动理论。作为生物体的简单模型，当二维有耗介质柱内部结构发生局部变化时，其散射电磁场随之改变。本文根据矩阵摄动理论导出了变化的散射场与介电常数，电导率之间的简明关系，并得到逆问题的各阶摄动解。     

改进的FDTD法分析研究无限长导体柱上棱边TM散射之间的相互影响

本文用改进的ＦＤＴＤ法（时域有限差分法）分析研究了带有棱边的无限长导体柱ＴＭ散射问题，以长方形导体柱为例，对棱边附近ＴＭ散射电流之间的相互影响进行了计算，数值计算结果表明棱边散射电流之间的相互影响比较明显，在近场问题中应特别予以考虑。在导体桂边附近的网格点上将近似场解直接引入差分方程，对ＦＤＴＤ方法进行了改进。同时本文对棱边周围的近场进行了分析计算，得出了棱边用导电劈近似处理的一些相关条件。     

Scattering of Electromagnetic Waves by a Coated Nihility Cylinder

An analytical solution for the scattering of electromagnetic plane waves from an infinitely long nihility cylinder, coated with a double positive (DPS), double negative (DNG), epsilon negative (ENG), or mu negative (MNG) layer of uniform thickness is presented. The solution is determined by solving the scalar wave equation in the cylindrical coordinates, for different regions and applying the appropriate boundary conditions at the interfaces. Both TM and TE polarizations as incident plane have been considered in the analysis. Comparison of behaviors of a coated nihility cylinder with a coated PEC cylinder has been made. It is noted that two situations are more closer for DNG coating as compared to DPS coating.     

导体柱RCS方向图的并行MATLAB快速分析

基于WINDOWS系统,提出了矩量法(MoM)快速分析导体柱RCS方向图的MATLAB并行计算方案.在新算法中,将计算任务(如:求RCS、阻抗矩阵和它的逆)分配给各个并行计算机,这些计算机利用在彼此间基于局域网搭建的共享空间,进行必要的数据交换,进而完成各自的计算任务.例算都表明所用算法成功地提高了计算速度,可解决个人计算机(PC)因内存偏小不能求解电大物体电磁场问题的困难.     

色散媒质覆盖导电体的瞬时散射

本文提出了修正的时域有限差分法（ＦＤＴＤ）来分析计算色散媒质中瞬变场问题，并采用普郎尼近似法使时域卷积可转化为违推计算，是充分利用现代计算机技术解决时域和宽带电磁场问题的一种有效手段。同时运用此方法对色散媒质中及色散媒质覆盖的导体目标瞬时域散射场进行了计算和分析，直观可靠地反映了其特性，并与传统的（非色散）ＦＤＴＤ方法计算的结果进行了比较，差别是显而易见的，为此必须重视色散媒质对瞬变场分析的影响。