S-parameter measurements yielding the characteristic matrices of MTLs

Abstract

A frequency domain method is presented which yields accurate characteristic matrices of uniform multiconductor transmission lines (MTLs). It uses simple two-port network analyzer S-parameter measurements of a set of open-circuit and short-circuited MTL configurations. Transversely inhomogeneous MTLs can be characterized accurately in their quasi-TEM propagation regime. The technique was used to determine the inductance and capacitance matrices of a low loss three conductor ribbon cable above a ground plane. Comparisons with numerically and analytically obtained data are given. Measurements are found to be repeatable for lines of length l<λ/4. The λ/4 requirement is not found to be a restriction in the MHz regime and only plays a role as line end effects become significant at GHz frequencies. Obtained accuracy is significantly better than previously reported results.