Microwave resonators incorporating ceramic YBaCuO helices

Measurements of the unloaded Q-factors of resonators incorporating YBaCuO helices are presented as a function of temperature. All of the bulk helices give unloaded Qs higher at 77 K for frequencies less than 1 GHz than equivalent wholly Cu structures. Approximate microwave modeling of the resonator gives surface resistances around 1 m Omega at 77 K and 500 MHz. Initial measurements on thick-film YBaCuO helices give Q values significantly lower than the bulk, probably due to dielectric loss in the zirconia substrate. The enhancement in Q over similar Cu resonators make these devices useful for demonstration purposes. For practical applications, however, it is unlikely that the improvement observed will affect the status of low-noise microwave oscillators and filters.