Three-dimensional Metal / Dielectric Composite Structure Of Electromagnetic Scattering Finite Element / Boundary Integral Method

The calculation of electromagnetic scattering from arbitrary shaped three-dimensional (3-D) metallic, dielectric and composed objects have been of considerate current interest owing to wide application. There are a variety of researches to deal with the calculation of scattering. This paper based on finite-element and boundary-integral (FE/BI) method includes two parts: First, lower-order FE/BI method modeling from tetrahedra. Secondly, higher-order FE/BI method modeling from curved hexahedra.Firstly, the three kinds of numerical methods, which are the differential equation method, the integral equation method and the hybrid method, to calculate the electromagnetic scattering from metallic, dielectric and composed objects are presented.Analysis and comparison of the three methods mentioned above is made in detail. In the first section, the principle and numerical implementation of FE/BI method is presented. Considering the convergence and interior resonant problem, TENENH formulation is employed to boundary-integral. Furthermore, weighted coefficient is introduced to combine different boundary-integral formulation to improve the condition number of matrix . Then, the solution of systemic equations of FE/BI is studied. Because the FE/BI matrix is either sparse partly or dense partly, hybrid algorithm is performed to solve systemic equations. However, the solution of FEM matrix equation is involved in every iterative step in hybrid algorithm. Considering symmetrical, striped and sparse FEM coefficient matrix, the storage strategy and solution of matrix equation is studied. In the last, FE/BI method is applied to deal with electromagnetic scattering from 3-D metallic, dielectric and composed objects.In the second section, a higher-order vector FE/BI method modeling from curved hexahedra is developed to electromagnetic scattering from 3-D metallic, dielectric and composed objects. Considering serious ill-conditioned FEM matrix obtained from higher-order method, column pivoting ILU preconditioner is proposed to speed up the convergence rate of GMRES to FEM matrix equation, and good results can be obtained.As a basic research work for electromagnetic scattering characteristics of the 3-D metallic, dielectric and composed objects, FE/BI method provides a powerful way in effective solution.