Unlike SPICE3, which uses the state-based approach to simulate lossy transmission lines, KSPICE simulates lossy transmission lines and coupled multiconductor line systems using the recursive convolution method. The impulse response of an arbitrary transfer function can be determined by deriving a recursive convolution from the Pade approximations of the function. NGSPICE is using this approach for simulating each transmission line's characteristics and each multiconductor line's modal functions. This method of lossy transmission line simulation has shown to give a speedup of one to two orders of magnitude over SPICE3E. Please note that the following two models will support only transient simulation, no ac.

Additional Documentation Available:

• S. Lin and E. S. Kuh, `Pade Approximation Applied to Transient Simulation of Lossy Coupled Transmission Lines,' Proc. IEEE Multi-Chip Module Conference, 1992, pp. 52-55.
• S. Lin, M. Marek-Sadowska, and E. S. Kuh, `SWEC: A StepWise Equivalent Conductance Timing Simulator for CMOS VLSI Circuits,' European Design Automation Conf., February 1991, pp. 142-148.
• S. Lin and E. S. Kuh, `Transient Simulation of Lossy Interconnect,' Proc. Design Automation Conference, Anaheim, CA, June 1992, pp. 81-86.