YBCO shielded LaAlO/sub 3/ dielectric resonators for stable oscillators

We have investigated dielectric resonators (SDROs) fabricated from single crystalline LaAlO/sub 3/ shielded by two epitaxial films of YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO). At the resonant frequency of the TE/sub 011/-mode of 5.6 GHz unloaded quality factors Q/sub 0/ of 8/spl times/10/sup 5/ at 20 K and 4/spl times/10/sup 5/ at 60 K were obtained. These values were limited by dielectric losses in LaAlO/sub 3/. At 50 K we obtained a a Q/sub 0/ of 2/spl times/10/sup 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 measure oscillator phase noise. At 60 K 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 1 kHz. For operation with Stirling coolers, microphonics dominates the noise properties.<
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