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

In this paper the distributed parameters method is applied to model the pro pagation 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 ev aluation of the expressions of the surface impedance (R-s + jX(s)) and the propagation constant (alpha + j beta) in YBaCuO microstrip lines. We have c onsidered not only the losses in the dielectric but also those in the metal lic ground plane. This method has been validated on a 5.3 GHz cutoff freque ncy low pass filter, consisting of YBaCuO microstrip lines of small (190 mu m) and large (2000 mu m) width deposited on LaAlO3 substrate. The match be tween 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 discuss ion has been carried out on the correction factors for fringe field effects in narrow microstrips. (C) 1998 Elsevier Science B.V. All rights reserved.