Research On Nested Equivalent Source Method For Target Electromagnetic Scattering Problem

Electromagnetic analysis of multi-scale targets is a challenge in the field of computational electromagnetics.In this dissertation,the fast integral equation algorithm for electromagnetic analysis of multi-scale targets is studied in detail.The multi-scale analysis of dielectric materials and non-uniform meshing are also studied respectively.We study the nested equivalent source approximation(NESA)used in the surface integral equation to analyze the multi-scale penetrable problem,which is a kind of low-rank compression method with high accuracy.In this chapter,we use the combination of NESA and the surface integral equation,in which the inner and outer regions are partially compressed to obtain better compression effect.And the accuracy of the method is analyzed under different dielectric constants.Then,we give the numerical demonstration of this algorithm by analyzing a dielectric sphere and compare the result with Mie.We also simulate the UAV to verify the multi-scale characteristics of this algorithm.The problem of fast analysis of low-frequency dense meshes are further expanded.An adaptive octree method is adopted in the nested equivalent source method based on the standard octree.The method is mainly for the target with a fine structure,which need local dense mesh.The compression between different size's groups is explored and the accuracy of the compression is also demonstrated.The validity of this method is verified by analyzing a metal sphere and the efficiency of this method is also analyzed by a monopole antenna array.In order to improve the method,a continuous-discontinuous Galerkin method is introduced to make the mesh more flexible.We also give the numerical verification of this algorithm by comparing the simulation result of a non-conformal mesh grid cylinder with commercial software FEKO,and its efficiency is verified by a monopole antenna array too.The memory consumption and iterative solving time are further reduced compared with the standard nested equivalent source algorithm,which improves the efficiency of electromagnetic radiation and scattering problem for the analysis of nonuniformly discretized targets.