Abstract
This thesis presents a thorough analysis of the ring resonator, and studies the use of the ring at millimetre-wave frequencies (above 30GHz). An equivalent circuit for the ring is derived which is useful for extracting data from measured circuits, and accounts for different loss mechanisms and loading effects of the feed circuit. New analysis is presented on the effects of curvature, which is shown to influence the resonant frequencies and cause radiation which increases the loss in the ring. As well as considering microstrip transmission line, circuits using stripline, slotline and coplanar strips were also fabricated and analysed. At millimetre-wave frequencies, fabrication accuracy is critical, and it is shown how non-uniformities on the ring affect the frequency response. As one of the main uses for the ring resonator is for measurement of transmission line dispersion, a full-wave mode solver has been created and implemented in Matlab which can robustly predict the dispersion characteristics of planar lines. This software is used to model some of the ring resonators that are deliberately operated at frequencies close to or above higher order mode cut off, which cannot be modelled with conventional simulation packages. Techniques developed in this thesis have been used to significantly extend the state of the art for the ring resonator, and this work presents the highest reported operating frequency for a microwave ring resonator. Circuits have been fabricated using a variety of techniques and materials, and practical measurements have been carried out at frequencies up to 220GHz - twice that previously reported, and giving excellent agreement with the computer predicted characteristics from the theoretical model.