Superconducting stripline resonator performance

Reliable techniques for evaluating the microwave properties of superconductors are essential in providing calibrated data for exchange between laboratories and for developing practical device designs. The authors are examining the techniques which utilize microwave stripline resonators. These resonators provide for the rapid measurement of microwave parameters in a repeatable fashion with minimal constraints on processing. Sandwiched microstrip line resonators are used to compare the performance at 4.2 K of OFHC copper and superconducting films of Pb, Nb, and YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) at C-band and X-band. Typical results for the Nb resonators show a loaded Q/sub L/ of about 8*10/sup 4/ with a transmission insertion loss of 5 dB at 3 GHz. Initial results on a YBCO a-axis film used as a ground plane in the Nb resonator yield a surface resistance value of about 10/sup -3/ Omega at 2.8 GHz. Preliminary results on the phase noise performance of a Nb resonator at 2.9 GHz are presented.<
>