Frequency-Temperature Compensated Whispering Gallery Mode Dielectric Resonator and Oscillator

A high-Q sapphire whispering gallery mode dielectric resonator is designed and fabricated and used to operate in a prototype oscillator. To annul the temperature coefficient of permittivity (TCP) of sapphire a composite sapphire-rutile is employed by placing thin rings of rutile at the opposite ends of the sapphire crystal. The resonator, though not completely optimized shows the turn-over temperature at around 92 K for the WGE6,0,0 mode at 9.98828 GHz. The maximum Q-value measured in this mode is of the order of 1.48×10^5 at the turnover temperature. The oscillator includes the high Q-resonator, an amplifier and a feedback loop containing a phase shifter and an attenuator. The phase shifter was inserted to adjust the correct mode for the oscillator. At turn-over temperature single sideband phase noise of the oscillator, measured using signal analyzer was～−90 dBc/Hz at 10 kHz offset which is actually limited by the sensitivity of the measurement set up.