Measurement of the Surface Resistance of HTc Superconductors on Different Substrates Using an Inverted Microstrip Resonator with Coupled Lines

We report on measurements of the average surface resistance of structured thin Y₁Ba₂Cu₃0₇-films between 0.7 and 3 GHz. The films are structured as a meanderline resonator. The coupling of neighboured lines is taken into consideration. The structured film is put together with two superconducting ground planes to an inverted microstrip structure. The quality factor of the resonator is measured. A comparison between the measurement and a calculation then connects the quality factor to the average surface resistance of the thin HT_c film and the loss factor of the substrates. We obtained results for films of different quality. The best films on LaAlO₃ showed average surface resistance values down to 0.06 m&#x at 77 K and only a weak dependence on the applied input power at low power levels.