Research on Microwave Oscillator Based on Cryogenically Cooled Sapphire Cavity

Microwave oscillator based on cryogenically cooled sapphire cavity has advantages of extremely high-Q factor and low noise, and thus it has a wide application prospect. On the basis of theoretical calculation by HFSS software, a sapphire dielectric resonator working at whispery gallery (WG) mode is developed. Cooperating with servo loop, an oscillator is constructed. In order to ensure high-Q factor, low-temperature device based on digital PID control program is used to stabilize temperature of the resonator within a range of 4.2-15 K, with fluctuation below 1 mK. To further reduce phase noise, Pound circuitry is used to control phase of the oscillating frequency signal. When oscillating frequency is 9.2 GHz, single sideband (SSB) phase noise is measured.