Tunable double-ended dielectric-loaded microwave resonator for frequency-stabilisation applications

Many applications require the presence of a dielectric inside a microwave resonator. The paper presents an analysis based on the mode-matching technique of a dielectric-loaded cavity that has a configuration which is more generalised than that first proposed by Amman and Morris. The cavity consists of a wave guide of rectangular cross-section filled with dielectric for part of its length and also for part of its transverse dimension, 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 cutoff inside the dielectric, but is below cutoff outside. Frequency tuning is possible via the tunable plungers. Computed results for the resonant frequencies and unloaded Q-factors are presented for anumber of cavity configurations. Close corroboration of the predicted resonance frequency by experiment has been obtained. Furthermore, the performance of a Gunn-effect diode oscillator employing such a dielectric-loaded cutoff waveguide cavity as the frequency stabilising agent is investigated experimentally.