TABLE OF CONTENTS The applications of dielectric materials at radio frequencies were first proposed by Rayleigh in 1897 [1] who established the waveguiding properties of a dielectric rod. In 1938, Richtmayer [2] proposed the use of dielectrics as resonators and studied spherical and ring resonators. The first designs for dielectric resonator filters were described by Cohn in 1968 [3], although material properties were too poor at that time for many real filtering applications. More recently the properties of dielectric materials have improved dramatically. Along with the advent of satellite and cellular communications this has resulted in an explosion in the applications for, and published material on, dielectric resonator filters.
A dielectric resonator consists of a cylindrical, cubic or other shaped piece of high dielectric constant material, known as a puck. In conventional operation the puck is held by a supporting structure of low dielectric constant inside a conducting enclosure, which does not contact the puck (Figure 7.1). Typically the relative permittivity of the puck is between 20 and 80 and the puck is remote from the enclosure with b ? a. At the resonant frequency most of the electromagnetic energy is stored within the dielectric. The enclosure stops radiation and because it is remote the resonant frequency is largely controlled by the dimensions and permittivity of the puck. The fields outside the puck are evanescent and decay rapidly with distance away from the puck. The remoteness of the enclosure ensures that the unloaded Q u factor is dominated by...
