Generalized scattering parameters of two-coupled transmission lines

Analytical formulas for the generalized scattering (S) parameters of a general two-coupled transmission line structure are derived based on a quasi-TEM analysis and the structure´s quasi-TEM propagating modes. A simple technique based on features of the generalized S-parameters is presented to obtain S-matrices of one-, two-, and three-port networks derived from the general four-port via terminating port impedances. A straightforward, systematic technique is presented to simplify S-parameters of circuits derived form the interconnection of subnetworks. The theory and techniques are applied in the analysis of a bandpass filter. Agreement with previous work is established.