Impact of a normally conducting surface layer on attenuation in high-T/sub c/ superconducting microstrip transmission lines

A two-dimensional (2-D) model is adopted to characterize high-T/sub c/ superconducting (HTS) microstrip transmission lines with a normally conducting surface layer. The model is verified by comparison with a full-wave analysis calculation for identical all-superconducting lines and by calculation of the current distribution and propagation properties for a normal conductor version of the microstrip. Estimates are obtained for the transmission line attenuation constant versus thickness and conductivity of the resistive surface layer. The results suggest that in situ deposition of a normal metal overlayer on the HTS film surface may be a viable technique to secure the long-term performance of microwave devices.