Fast time domain simulation in SPICE with frequency domain data

The capability of time domain simulation with frequency domain data exists in some time-domain simulators, but the computations can be time-consuming. We decrease this computational burden by exploiting S-parameter fitter and fast recursive convolution methods. With recursive convolution the frequencies at which the S-parameters are sampled may be spaced in any way. For example, a logarithmic frequency spacing allows S-parameters to be sampled over a broader band without increasing the number of frequencies measured. We use two different system identification techniques for extracting the closed-form equations describing measured or simulated S-parameter data. Lumped parameter systems are approximated as a rational polynomial modulated by a complex exponential. Distributed parameter systems are approximated by the sum of complex exponentials. The recursive convolution engine handles both forms. The HP SPICE circuit simulator has been extended to allow fast, recursive convolution methods to be employed for transient analysis. The resulting simulator is called SSpice v2. Significant speed-up in the simulation of several circuits have been achieved using this new technique compared to both the traditional approach in SPICE and our previous direct-convolution-based approach in SSpice v1. In this paper, we present the algorithms and applications of the simulator. Three applications are demonstrated in the paper which are MR head flex line modeling, chip-to-chip signal modeling on MCM, and on-chip inductor modeling