A 10 GHz Y-Ba-Cu-O/GaAs hybrid oscillator proximity coupled to a circular microstrip patch antenna

A 10-GHz hybrid Y-Ba-Cu-O/GaAs microwave oscillator proximity coupled to a circular microstrip antenna has been designed, fabricated, and characterized. The oscillator was a reflection mode type using a GaAs MESFET as the active element. The feedline, transmission lines, RF chokes, and bias lines were all fabricated from YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting thin films on a 1-cm*1-cm lanthanum aluminate substrate. The output feedline of the oscillator was wire bonded to a superconducting feedline on a second 1 cm*1 cm lanthanum aluminate substrate, which was in turn proximity coupled to a circular microstrip patch antenna. Antenna patterns from this active patch antenna and the performance of the oscillator measured at 77 K are reported. The oscillator had a maximum output power of 11.5 dBm at 77 K, which corresponded to an efficiency of 10%. In addition, the efficiency of the microstrip patch antenna together with its high temperature superconducting feedline was measured from 85 K to 30 K and was found to be 71% at 77 K, increasing to a maximum of 87.4% at 30 K.< >