Automated Framework for Time-Domain Piecewise-Linear Fitting Method Based on Digital Wave Processing of $S$ -Parameters

An innovative full time-domain macromodeling technique for general, linear multiport systems is described. The methodology is defined in a digital wave framework and time-domain simulations are performed via an efficient method called Segment Fast Convolution (SFC). It is based on a piecewise-constant (PWC) model of the impulse response of scattering parameters, computed starting from a piecewise-linear fitting of their step response (PWLFIT). Such step response is directly available from time-domain reflectometer measurements (TDR/TDT) or equivalent simulations. The model-building phase is performed in a fast automated framework and an analytic formulation of computational efficiency of the SFC with respect to the standard time-domain convolution is given. Two application examples are used to verify the PWLFIT performance and to perform a comparison with macromodeling methods defined in the frequency-domain, such as Vector Fitting (VF).