Automated microwave measurements of microstrip ring resonators at low temperatures

The high frequency properties of both substrates and superconducting materials have been determined from relatively large area microstrip resonator circuits mounted in an automated measurement system. Properties such as dielectric constant and surface resistance are presented for a variety of materials, such as YBa/sub 2/Cu/sub 3/O/sub 7-x/, Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/, Cu and Ag on either yttria-stabilised zirconia, MgO or plastic substrates. The surface resistance of thick film YBa/sub 2/Cu/sub 3/O/sub 7-x/ ring resonators on yttria-stabilised zirconia substrates were found to be limited by the loss tangent of the substrate while the surface resistance of similarly-sized Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ thin film ring resonators on MgO substrates showed a marked power dependence. At 3 GHz the surface resistance of thick film YBa/sub 2/Cu/sub 3/O/sub 7-x/ on yttria-stabilised zirconia at -10 dBm was found to be superior to thin film Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ on MgO below T/sub C//2 as a result of better power handling.