Assessment of coupled transmission lines embedded between imperfectly matched differential circuit stages

Abstract

This paper presents a methodology to assess the performance of edge-coupled transmission lines when interconnecting imperfectly matched circuit stages. The methodology considers common and differential mode signal propagation, and allows for the prediction of reflection and transmission of signals as if the channel is already operating within a practical circuit. This is achieved by means of a procedure involving embedding and de-embedding impedances to S-parameter data to allow for the straightforward transformation to mixed-mode S-parameters using the desired impedance terminations. The application of the proposal is shown even for the case where the output impedances (i.e., common and differential) of the driver differ from the input impedances of the receiver.