Full Wave Analysis of Normal and Superconducting Microstrip Transmission Lines

Abstract

We present a full wave analysis to compute the propagation constant of electromagnetic waves traveling in a normal and superconducting microstrip transmission line. The transverse wavenumber in the dielectric substrate is obtained as the root of a set of transcendental equation, derived by matching the tangential fields at the dielectric-conductor and dielectric-air interfaces. The propagation constant can then be obtained by substituting the transverse wavenumber into the dispersion relation. For normal microstrip lines, we found good agreement between our results and those obtained using the quasi-static methods. As compared to some of the available techniques used to calculate loss in superconducting microstrip lines, such as Maticks and Yassin-Withingtons method, our method gives higher loss especially in the regime of millimeter and submillimeter wavelengths. Since our method takes into account the superposition of TE and TM modes, we attribute the differences as due to the fringing fields effect and the existence of the longitudinal field components in our formulation.Index Terms -propagation constant, superconducting microstrip, dispersion relation, submillimeter wavelengths, fringing fields effect. Formulation Fields in the dielectric substrateThe microstrip configuration analyzed here is partially enclosed as indicated in Fig. 1. The sidewalls at x = AEa/2 are perfectly conducting and the width a approaches infinity so Frequenz 64 (2010) 3-4