Moment Method Analysis of Antennas in Reverberation Chambers and Cylindrical Structures

Licentiate thesis, 2004

This thesis is a collection of papers using the method of moments for numerical analysis. The papers can be divided into two main groups; a study of antennas in reverberation chambers, and a study of antennas in cylindrical structures. The reverberation chamber is a metal cavity for measuring antennas and other devices. A numerical model of the reverberation chamber is developed to be able to better understand the field environment in the chamber and improve the performance of the chamber. The effect of lossy objects in the reverberation chamber is studied by calculating the mean absorption cross section of lossy objects and comparing it to measurements in a reverberation chamber. The possibility to extract electrical parameters of dielectric objects by measuring the mean absorption cross section is shown. The second part of the thesis deals with cylindrical structures. Many waveguide and antenna structures can be assumed to be infinitely long in one of the coordinates. It is then possible to efficiently solve a spectrum of two-dimensional problems rather than to solve the complete three-dimensional problem. The present thesis show solutions for modes in waveguides with various electromagnetic band-gap surfaces. Also it is shown how the field solutions for cylindrical structures can be interpolated over the spectral domain with the asymptotic waveform evaluation technique. There is also one paper analyzing a high-Q resonator on dielectric substrate by solving the onedimensional numerical Green's function for multi-layer planar structures.