Frequency stability of dielectric loaded HTS microwave resonators

High Q dielectric loaded superconducting resonators have many potential microwave applications. A key issue for many of these is the stability with which the resonant frequencies of such resonators may be realised, for use as frequency references etc. We report experiments on a number of different resonator geometries using YBCO thick films as planar shields for composite dielectric structures. The experimental results are analysed and surface impedance data as a function of temperature and frequency is deduced for each superconductor specimen as well as real and imaginary components of the relative permittivity of each dielectric material involved in the resonators. Using these parameters predictions are made for the attainable stability in realistic resonator structures. We compare these predictions with stability requirements for a number of wide ranging and niche applications.