Simplified method to evaluate weakly nonlinear communication circuits

This paper reports a simplified method to efficiently analyze weakly nonlinear circuits excited by communications signals. The proposed technique is based on the envelope current approach. The method is first theoretically demonstrated, and subsequently tested with two-tone excitation and in the case of digitally modulated signals, exhibiting in these cases reduced simulation times. For validation purposes, a single-FET amplifier has been constructed and characterized with single- and two-tone input RF signals at 2 GHz, and also the output spectra under UMTS-WCDMA signal excitations above the 1-dB compression point have been obtained. In addition to the reduced times, presented simulations demonstrate a good agreement with experimental results. The close correspondence between calculated and measured spectral regrowth will enable a reliable prediction of ACPR.