Properties of mixed-mode parameters of cascaded balanced networks and their applications in modeling of differential interconnects

The cascading properties of general four-port networks are explored with respect to the standard to mixed-mode transformation of scattering matrices. Rigorous proofs are given to show that, for balanced networks, the odd-/even-mode scattering matrix of two cascaded networks equals the scattering matrix of the cascade of the respective odd-/even-mode networks. This concept is used to extract physical equivalent-circuit models for coupled backplane vias, differential package traces, and differentially routed data pins of XDR memory devices.