任意形状天线罩的快速分析

将自适应积分算法与体积分方程相结合分析任意形状天线罩对天线辐射特性的影响。将任意形状的天线罩剖分成四面体，基于体积分方程的自适应积分快速算法求出天线罩上的感应电流，即可求出天线-天线罩系统的总场。自适应积分快速算法的应用提高了矩量法的计算速度，并大大缩减了需要的存储量，从而使该方法可用于分析电尺寸较大的天线罩.最后,分别计算了球形、锥形天线罩存在时理想电振子阵列的辐射方向图。     

A volume-surface integral equation method for solving Maxwell'sequations in electrically inhomogeneous media using tetrahedral grids

Starting with the solution of Maxwell's equations based on the volume integral equation (VIE) method, the transition to a volume-surface integral equation (VSIE) formulation is described. For the VSIE method, a generalized calculation method is developed to help us directly determine E fields at any interface combination in three-dimensional (3-D) electrically inhomogeneous media. The VSIE implementation described is based on separating the domain of interest into discrete parts using nonuniform tetrahedral grids. Interfaces are described using curved or plane triangles. Applying linear nodal elements, a general 3-D formulation is developed for handling scatter field contributions in the immediate vicinity of grid nodes, and this formulation is applicable to all multiregion junctions. The special case of a smooth interface around a grid node is given naturally by this formulation. Grid nodes are split into pairs of points for E-field calculation, and node normals are assigned to these points. The pairs of points are assigned to the elements adjoining the grid node. For each pair of points, the correct field jumps on the interface are given by a surface integral over the polarization surface charge density     

Scattering and radiation from planar structures containing smallfeatures using a finite element-fast integral method

Fast integral equation algorithms such as the adaptive integral method (AIM) have been demonstrated to reduce memory and execution time associated with moment method solutions for computing electromagnetic scattering and radiation from arbitrarily shaped three-dimensional geometries. The authors examine the efficiency of AIM in modelling planar structures that contain small and intricate details as is the case with spirals and slot antennas. Such geometries require high tessellation due to the inclusion of very small features resulting in a large number of unknowns. The AIM, with its ability to translate the original grid into an equivalent sparser uniform grid, is uniquely suited to the analysis of such geometries. The application of the AIM in connection with finite element-boundary integral formulation for cavity-backed antennas is also presented     

Electromagnetic scattering by inhomogeneous dielectric bodies ofrevolution embedded within stratified media

A method of moments (MoM) solution for scattering by heterogeneous bodies of revolution (BOR) embedded within a multilayered environment is given. A modal volume integral equation (VIE) is formulated in the mixed potential form and solved with the use of the specialized basis functions     

Surface integral representation radiation boundary condition forthe FDTD method

A radiation boundary condition for the finite-difference-time-domain (FDTD) method is presented. It is based on a time-domain integral representation of the electromagnetic fields outside the calculation volume in terms of the known fields on a surface surrounding that volume. Numerical evaluation of the method shows that its performance is superior to that of existing radiation boundary conditions     

Conformal Galerkin testing for VIE using parametric geometry

A moment method solution of a volume integral equation (VIE) using parametric geometry is presented. Typical Galerkin testing is shown not to be appropriate for curvilinear geometries, and a new testing scheme is proposed. By exploiting the orthogonality relationships between covariant and contravariant unitary vectors, testing functions in contravariant projection form and field expansion basis in covariant projection form were chosen.     

Method of moments solution for a printed patch/slot antenna on a thin finite dielectric substrate using the volume Integral equation

In this paper, a volume integral equation (VIE)-based modeling method suitable for a patch or slot antenna on a thin finite dielectric substrate is developed and tested. Two new key features of the method are the use of proper dielectric basis functions and proper VIE conditioning, close to the metal surface, where the surface boundary condition of the zero tangential E -component must be extended into adjacent tetrahedra. The extended boundary condition is the exact result for the piecewise-constant dielectric basis functions. The latter operation allows one to achieve a good accuracy with one layer of tetrahedra for a thin dielectric substrate and thereby greatly reduces computational cost. The use of low-order basis functions also implies the use of low-order integration schemes and faster filling of the impedance matrix. For some common patch/slot antennas, the VIE-based modeling approach is found to give an error of about 1% or less in the resonant frequency for one-layer tetrahedral meshes with a relatively small number of unknowns. This error is obtained by comparison with fine finite-element method (FEM) simulations, or with measurements, or with the analytical mode matching approach. Hence it is competitive with both the method of moments surface integral equation approach and with the FEM approach for the printed antennas on thin dielectric substrates.     

Volume integral equations for analysis of dielectric branchingwaveguides

Novel forms of volume integral equations are developed for the exact treatment of wave propagation in two-dimensional dielectric branching waveguides. The integral equations can be obtained by considering the condition at a point far away from the junction section. An approximate solution by the Born approximation and a numerical solution by the moment method establish the validity of the new volume integral equations. The numerical results are discussed from the viewpoint of energy conservation and reciprocity. The solution is exact if sufficiently large computer memory and computational time are used. The method can be extended to problems of a more general nature (i.e. the incident TM mode), and complex configurations of branching waveguides. The basic idea is also applicable to techniques using boundary (surface) integral equations which are applicable to three-dimensional problems     

金属介质混合目标电磁特性的快速分析

将自适应积分算法与基于体面混合积分方程的矩量法相结合快速分析任意结构金属/介质混合目标的电磁散射和辐射特性.通过将传统矩量法的阻抗矩阵分为两部分且采用不同的方法进行处理计算,提高了矩量法的计算速度并大幅度缩减了需要的计算机内存占用量.最后,分别用传统的矩量法与结合自适应积分快速算法的矩量法计算了三个典型例子,通过比较充分说明了文中方法的有效性.     

金属骨架结构对天线罩散射特性的影响*

在轮廓尺寸确定的情况下,天线罩金属骨架的结构划分对其电磁性能起着至关重要的作用。从骨架 拓扑结构的角度出发,研究了不同结构对骨架散射特性的影响。通过构建物理参数一致的规则和非规则金属骨架, 采用感应电流率理论得出骨架不同位置的感应电流分布,最后确定骨架的扩散场影响。结果表明,非规则划分的金 属骨架,由于桁杆在球面上近似为随机分布,远区散射能量被分配到了偏离主辐射方向的旁瓣区域,主辐射方向相 对于规则骨架的影响要小很多。应用非规则划分方法设计的骨架,可以有效提高天线罩的性能。