Modeling of microstrip quasi-TEM superconducting transmission lines, comparison with experimental results

In this paper the distributed parameters method is applied to model the propagation of microwave in a microstrip line of YBaCuO with different widths. This method is based on the two-fluid model and proceeds on an accurate evaluation of the expressions of the surface impedance ( R s+ jX s) and the propagation constant ( α+ jβ) in YBaCuO microstrip lines. We have considered not only the losses in the dielectric but also those in the metallic ground plane. This method has been validated on a 5.3 GHz cutoff frequency low pass filter, consisting of YBaCuO microstrip lines of small (190 μm) and large (2000 μm) width deposited on LaAlO 3 substrate. The match between experimental and simulation results is quite well from 60 to 89 K so the quasi-TEM approach is confirmed until 7 GHz. Moreover, a useful discussion has been carried out on the correction factors for fringe field effects in narrow microstrips.