Measurement of YBCO Thin Film Surface Resistance Using Coplanar Line Resonator Techniques From 20 MHz to 20 GHz

The surface resistances of YBCO thin films are measured over a wide and continuous frequency range from 20 MHz to 20 GHz, by characterizing more than 1000 harmonics of two 20 MHz high-temperature superconductor resonators. One resonator is based on the conventional coplanar waveguide (CPW) and the other based on the conductor-backed CPW (CBCPW). The quality factors and resonant frequencies are measured. The attenuation and group-delays of the coplanar lines are estimated and surface resistances of the superconductors are extracted using a transmission-line model. The wideband frequency-dependence of the surface resistance is investigated. The sources of experimental errors are analyzed. This paper also reports some temperature-dependent and power-dependent measurement results.