Spectral Models of Lossy Nonuniform Multiconductor Transmission Lines

This paper presents a new approach for modeling nonuniform lossy transmission lines. The proposed technique is based on the concept of Green´s function of the differential problem represented by the Telegrapher´s equations. The Green´s function of nonuniform one-dimensional problems is expanded in terms of the eigenfunctions of the uniform problem, yielding a rational macromodel that has a simple representation in the time-domain. The use of global basis functions also addresses the problem of space dependence of the per-unit-length parameters, completely avoiding to resort to any discretization technique. Several examples of single and coupled nonuniform lines are presented and the accuracy of the method is verified by comparison with reference results.