A film transmission line resonator to measure the microwave surface resistance of YBa/sub 2/Cu/sub 3/O/sub 7-x

The authors constructed microstrip transmission line resonators with YBa/sub 2/Cu/sub 3/O/sub 6.9/ ground planes, SiO dielectric, and Nb top conductors. The film resonator is a low-impedance section n lambda /2 long, and the wave is launched from a coaxial line. Loose coupling is provided by the discontinuity between 50- Omega feed lines and the 0.05- Omega resonator section. After de-embedding the transmittance data of the structure, the surface resistance of the ceramic superconductor can be computed. The surface resistance of YBa/sub 2/Cu/sub 3/O/sub 6.9/ at 4.2 K was about a factor of 60 higher than the theoretical value for Nb at 4.2 K over the range 2.9-6 GHz. The power law behavior versus frequency of the surface resistance is roughly quadratic, which is consistent with two-fluid analysis.< >