Numerical Methods For Analyzing Electromagnetic Scattering From Electrically Large Concave Objects In Complicated EM Environments

Numerical methods for analyzing scattering from electrically large objects are always in the spotlight in computational electromagnetics. For large convex objects, geometrical/uniform theory of diffraction (GTD/UTD), physical theory of diffraction (PTD) and hybrid techniques combining GTD, PTD and other numerical methods such as moment methods (MOM) and finite element methods (FEM) may be used to evaluate convex objects'EM scattering. Additionally, fast algorithms such as adaptive integral method (AIM) and multilevel fast multipole method (MLFMM) could be made use of in the conditions of high computing accuracy. However, there exist a lot of concave objects in EM world, for example, reflection antennas and inlets of airplanes. Therefore, it is necessary to study numerical and asymptotic methods for computing scattering by electrically large concave objects such as cavities.In this thesis, two iterative methods for evaluating electromagnetic scattering from concave objects are studied through a set of integral equations and a set of matrix equations together with their iterative forms which are derived from Stratton-Chu formulations. Specific knowledge about the theories, iteration performances of the two iterative methods together with their modified forms and the relationship between them are illuminated. In addition, compute programs for electrically small, medium and large objects including convex and concave perfectly electric conductors are developed with the help of three-dimensional point matching functions, RWG functions and singularity extraction. Numerical expressions for program implementaion are derived in detail and some simulation results with the computer programs are given.