Electromagnetic scattering analysis of elliptically shaped structures

Abstract

Electromagnetic diffraction from cavities and wedge and transmission through slots is an old one and has been considered by many researchers. The reason for it is because the determination of scattered field due to the presence of cavities, slot and wedge is a very real problem. Such geometries occur in a number of applications, such as cavities backed slot antennas, microstrip line to slot coupling for microwave lens antennas. Research has shown that such cavities, slots can significantly change the scattered field and thus its RCS (Radar Cross Section). In general, because most problems are dependent on their geometries in the areas of microwave society, various geometries has been considered to improve antenna beam pattern and bandwidth of waveguide, control RCS by many researchers. Elliptic geometries have also been used to shape the beam patterns of elliptic cavity backed slot antenna and slot coupled lens antennas. In this dissertation, fast convergent and efficient rigorous solutions based on Mode Matching Method (MMT) and Mathieu functions, wave functions in the elliptic coordinates, are presented for electromagnetic scattering from elliptic cavities, slots and an edge in a convex conducting body. These solutions are fast convergent and more general than those based on circular cylindrical wave functions. Furthermore, a new kind of dual mode filter using elliptic ring resonator is also presented for rejection of image frequency at 2.4 and 2.8 GHz bands. This dissertation consists of four parts. First, electromagnetic diffracted solutions for an elliptic cavity with/without slot are formulated for a plane wave incidence. The total fields consist of incidence, reflected and diffracted fields. And diffracted fields is represented in terms of transmitted field inside elliptic dielectric cylinder and diffracted field satisfying the radiation condition. The difference between an elliptic cavity backed slot and a cavity without a slot is presented with th...