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 YBa₂Cu₃O_7-δ and Tl₂Ba ₂CaCu₂O₈ 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 YBa₂ Cu₃O_7-δ 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 resonators 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 DROs and SAWOs at 12 GHz