Applications of coupled dielectric resonators using SrTiO/sub 3/ pucks: tunable resonators and novel thermometry

The combination of very low loss dielectric single crystal materials with a HTS shielding enclosure provides high Q resonators in the temperature range 40-70 K which show great promise for frequency standard applications. We report electronic tuning of a sapphire dielectric puck resonator by using a SrTiO/sub 3/ tuning element situated in the evanescent field region outside the sapphire puck. In addition when the sapphire and SrTiO/sub 3/ elements act as weakly coupled resonators, the resonant frequency becomes a very sensitive function of temperature, allowing the possibility of very high resolution thermometry.