S-parameter measurements yielding the characteristic matrices of multiconductor transmission lines

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. The method eliminates the need for voltage and current probes, which introduce errors. Transversely inhomogeneous MTLs can be accurately characterized in their quasi-TEM propagation regime. The influence of the skin effect on the inductance matrix is taken into account. 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 megahertz regime and only plays a role as line-end effects become significant at gigahertz frequencies. The obtained accuracy is significantly better than previously reported results