An efficient envelope transient simulation of S-Parameters circuits in system simulator

Abstract : We present here a novel approach on behavioral modeling of passive RF blocks from frequency domain samples. This approach combines the vectorfitting (VF) algorithm, which is a powerful iterative method for estimating the poles and residues of a MIMO system, associated with the inverse Laplace transform in order to implement passive RF models in a time domain system simulation environment. For our application, the Scilab/Scicos tool is chosen since it allows the resolution of implicit equations, therefore, the implementation of bilateral behavioral models. The impulse responses Sij(t) are then evaluated form previous poles/residues identification process in order to compute the implicit relationship between I and V at each port of the block. This method has been validated in the case of simple circuit (load) and extended to the case of complex MIMO sub-systems such as a full power combiner of a power amplifier (PA). As a result, the envelope transient (TE) S-parameters evaluation of circuits is possible. Thence, the evaluation of complex PAs is submitted to an actual signal (which often includes linear sub-circuits derived from Momentum simulation).