4.1 Introduction

An accurate mathematical description of the electromagnetic field in a dielectric resonator (DR) is considerably more complicated than the field description in a hollow waveguide resonator. If the numerical result for a DR is to be obtained for a given set of dimensions, a large computer is traditionally required because of the large size of the matrices involved and the large number of operations which has to be performed.

It is of great practical interest to approach the solution of the electromagnetic field in the DR in some simplified way that is still capable of giving results which are not too far from the exact values. Two such simple mathematical models of DR to be described here are the Cohn model and the Itoh and Rudokas model. Before the Cohn model is described, a brief review of the notion of the perfect magnetic conductor will be presented in the next two sections.

4.2 Notion of the Magnetic Conductor

Consider a textbook case of the plane wave incident on the interface of two different dielectric media as shown in Fig. 4.1. To make the situation as simple as possible, assume that the direction of the plane wave is normal to the interface, i.e., the incident wave propagation is oriented in the of positive z-direction. Then, a part the energy of the incident wave will be reflected back from the interface as a plane wave traveling in the negative z direction in medium 1. The rest of the...