Implementation of Broadband Transmission Line Models with Accurate Low-Frequency Response for High-Speed System Simulations

摘要

As data rates for high speed interconnect systems reach multi-gigaherz data rates, accurate modeling of transmission lines becomes increasingly important. However, it is rather difficult to obtain broadband transmission line models, in particular using frequency domain S-parameters. In this paper, we examine two potential accuracy problems associated with generating transmission line models from S-parameters. First, we demonstrate the time-domain inaccuracies due to the low-frequency limitation of the frequency domain techniques. Our solution is to use additional time-domain TDR measurements for deriving the necessary constraints at the low frequency. Next, we propose a novel de-embedding technique for eliminating port discontinuities as part of the general formulation for deriving N-port coupled lossy transmission line parameters from S-parameters. Finally, several numerical examples, such as MCM-L coplanar lines and package microstrip lines, are studied to illustrate the accuracy of the proposed method.