High thermal stability microwave oscillator based on HTSC resonator

Recent developments in high temperature superconducting (HTSC) thin films have made possible the construction of microwave resonators with a very high Q values because of the significantly lower surface resistance than that of normal metals. In this paper microwave characteristics of microstrip resonators fabricated from YBa2Cu3P7-delta and Tl2Ba2CaCu2O8 thin films were studied and their application for stabilization of a microwave oscillator was shown. Two oscillators were fabricated and tested, one at 4 GHz with YBa2Cu3O7-delta meander-type resonator and a hybrid oscillator implemented on RT/Duroid substrate and Tl2Ba2CaCu2O8 linear microstrip resonator operated at 12 GHz. The designs were parallel feedback mode oscillators and transmission-type high-Q HTSC resonator were used as bandpass filters. A frequency instability of the hybrid oscillator with Tl2Ba2CaCu2O8 resonator of -0.16 ppm/K at 77 K was achieved which exceeds that possible with state-of-the-art DRO's and SAWO's at 12 GHz.