Phase-Locking of a Gunn Oscillator at 3mm Waveband Using HighTemperature Superconducting Josephson Junction Harmonic Mixer

A Gunn oscillator at 3mm waveband has been phase-locked to a synthesizer local oscillator using a high T_c YBa₂C₃O_7-δ Josephson junction operated at 77K as the harmonic mixer, with harmonic numbers up to 52. The observed spectrum of the phase-locked output at the intermediate frequency (IF) shows clearly that the quality of the phase-locking is very good. To drive the analogue phase locking loop successfully, it is essential to have IF output and signal-to-noise ratio both as high as possible.