Analysis of a Tunable Double-Ended Dielectric-Loaded Microwave Resonator

Many applications require the presence of a dielectric inside a microwave resonator. This paper presents an analysis based on the mode matching technique [1] of a dielectric-loaded cavity that has a configuration which is more generalised than that first proposed by Amman and Morris [2]. The cavity consists of a waveguide of rectangular cross-section filled with dielectric for part of its length and for part of its transverse dimension as well, with movable shorting plungers in the guide beyond both ends of the dielectric. Such a structure supports resonances at frequencies where a particular waveguide mode is above cut-off inside the dielectric, but is below cut-off outside. Frequency tuning is possible via the tunable plungers. Computed results for the resonant frequencies and Q-factors are presented for a number of cavity configurations. Close corroboration of the theory with experiment has been obtained.