Time-domain Simulation of Passband S-parameter Networks Using Complex Baseband Vector Fitting

This paper presents a simple and accurate extension of Vector Fitting for the inclusion of bandpass linear time invariant (LTI) frequency-domain data within a nonlinear baseband time domain simulation. The time-domain response is obtained as a complex-valued sum of decaying exponentials, which may be then convolved with the complex baseband form of the input signal to obtain the corresponding complex baseband output. This allows networks which are most accurately described in the frequency domain, such as frequency-dispersive transmission lines, to be included as part of a general time-domain nonlinear circuit solver. While the method is general, this contribution utilises bandpass frequency-domain data in the form of network scattering parameters.