Resonators for a 2 pole filter fabricated from YBCO coated LaAlO/sub 3/ cylinders

We prepared and tested dielectric resonators designed for a two pole filter. These resonators were LaAlO/sub 3/ single crystalline cylinders which were covered on the end faces by about 350 nm YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin films and on the cylindrical surface by 4 /spl mu/m gold films. The YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films were c-axis oriented with mosaic spreads of about 0.3/spl deg/. The inductive transition temperatures were above 90 K. The HF properties were characterized by evaluation of the H/sub 011/ mode at 8.05 GHz, and by measuring the surface resistance at 18.9 GHz. At 77 K the Q-value of this resonance was typically 12000, which is about a factor of 2 higher than the Q-value of 6560 found for end faces covered with pure copper. From these resonators two-pole bandpass filters were constructed that at 77 K showed an insertion loss of -0.26 dB at their center frequency of 6.3 GHz.