Study On The Fast Algorithm For Electromagnetic Scattering From Composite Conducting And Anisotropic Objects

In recent years, the analysis of electromagnetic scattering by anisotropic objects has received wide attention because of its academic challenge in difficulty and importance in various applications. The effective reduction of the radar cross section (RCS) by using the anisotropic medium coated on the surface of aircrafts promotes the development of the stealth technology and anti-stealth technology. Therefore, research on the characteristics of electromagnetic wave scattering from these anisotropic media-coated targets is one of most important topics in the military electronic area. The conventional computational methods have been used to solve electromagnetic problems including the electrical small objects with the simple geometry such as sphere or cylinder due to the complexity of the anisotropic medium. Therefore, this thesis focuses on the study of electromagnetic scattering by the electrically large anisotropic objects.In this thesis, the higher-order (method of moments) MoM is developed to analyze electromagnetic scattering from the anisotropic objects. Compare with the low-order MoM, the higher-order MoM can dramatically decrease the number of unknowns in order to reduce its memory requirement with high computational accuracy. In the higher-order MoM, the higher order hierarchical basis functions consisting of the modified Legendre polynomials are of good orthogonality. The RCS solutions of the PEC sphere, anisotropic cube and anisotropic medium-coated PEC sphere are in agreement with the analytical results or the results in some published papers, and it can be found from some numerical examples that the anisotropic media coated on the surface of conducting objects can reduce the RCS. The numerical results indicate that the developed higher-order MoM in this thesis is a high efficient tool for the analysis of electromagnetic scattering problems including anisotropic objects.Besides, the volume and surface integral functions (VSIE) is applied into a fast algorithm named multilevel Green's function interpolation method (MLGFIM) to analyze the electromagnetic scattering by inhomogeneous anisotropic objects. The proposed method can decrease the computational complexities from O ( N~2) in traditional MoM to between O (N) and O ( NlogN). And its memory complexities are decreased from O ( N~2) to O (N). The RCS results of anisotropic sphere, anisotropic medium-coated PEC sphere, anisotropic cavity and patch array are nearly same as the Mie series results or the results in some published papers. The numerical results show that the VSIE solved by the MLGFIM used to analyze the anisotropic media is doable and efficient.