HIGH-T-C SUPERCONDUCTIMG THIN FILM GAAS MESFET HYBRID MICROWAVE-OSCILLATOR/

A high-T-c superconducting (HTSC) thin film/GaAs MESFET hybrid microwa ve oscillator operated at 10.6 GHz has been designed, fabricated and c haracterized. Microstrip line structures were used throughout the circ uit with superconducting thin film YBa2Cu,O-3(7-delta)(YBCO) as the co nductor material. The YBCO thin films were deposited on 15 mm x 10 mm x 0.5 mm LaAlO3 substrates. The oscillator was common-source, series f eedback type using a GaAs-MESFET (NE72084) as the active device and a superconducting microstrip resonator as the frequency stabilizing elem ent. By improving the unloaded quality factor Q(0) of the superconduct ing microstrip resonator and adjusting the coupling coefficient betwee n the resonator and the gate of the MESFET, the phase noise of the osc illator was decreased. At 77 K, the phase noise of the oscillator at 1 0 kHz offset from carrier was -87 dBc/Hz.