YBCO SHIELDED LAALO3 DIELECTRIC RESONATORS FOR STABLE OSCILLATORS

We have investigated dielectric resonators (SDROs) fabricated from sin gle crystalline LaAlO3 shielded by two epitaxial films of YBa2Cu3O7 (Y BCO). At the resonant frequency of the TE(011)-mode of 5.6 GHz unloade d quality factors Q(0) of 8 x 10(5) at 20K and 4 x 10(5) at 60K were o btained. These values were limited by dielectric losses in LaAlO3. At 50K we obtained a Q(0) of 2 x 10(5) at a level of dissipated rf power of 2 W corresponding to an average rf magnetic surface field of 150Oe. Moreover, we used one SDRO as a feedback for a HP8349 amplifier to me asure oscillator phase noise. At BOK and helium gas cooling the phase noise was beyond the sensitivity limit of our HP8565 spectrum analyzer of about -90dBc/Hz at an offset frequency of 1kHz. For operation with Stirling cooler microphonics dominates the noise properties.