A universal closed-loop high-speed interconnect model for general purpose circuit simulators

In this paper a novel technique is presented for the computation of multiconductor transmission line stencils suitable for inclusion in general purpose circuit simulators such as SPICE. Transmission lines can be lossy, coupled and distributed. The method offers an efficient means to discretize transmission lines compared to the conventional lumped discretization. Coefficients of the approximation are computed using closed-loop Pade approximants of exponential matrices. The algorithm also provides an error criterion for automatically selecting the order of the approximation for the frequency-bandwidth of interest. Numerical examples are presented to demonstrate the validity of the proposed model and to illustrate its application to variety of interconnect structures.