Temperature compensated cryogenic whispering gallery mode resonator for microwave frequency standard applications

We have investigated a miniature composite dielectric resonator employing a sapphire puck and a single crystalline platelet of rutile, excited in a whispering gallery mode. Modeling of the relative filling factors of the dielectric components is in good agreement with experiment. The loaded Q value at 17 GHz is as high as 3/spl times/10/sup 6/. We have achieved values of the square-root of the Allan variance as low as 3/spl times/10/sup -12/ for an integration time of 1000 s with the prototype system. The high and resonator can also form the basis for a low-phase noise oscillator and we present data for the measured spectral density of phase noise.