High-Q microwave properties of a sapphire ring resonator

The high-Q microwave properties of a sapphire dielectric ring resonator in the frequency ranges 8-12 GHz and 18-22 GHz at both room temperature and low temperature are discussed. The Q of the resonator is limited significantly below the loss tangent limit, but the frequency stability is excellent when compared with other types of resonator. The results indicate that the sapphire ring resonator should be well suited for use in long-term, high-stability frequency standards, and should also be useful for phase noise stabilisation of microwave sources.