A scalable rf large-signal model of quasi-enhancement-mode AlGaAs/InGaAs pHEMTs has been purposed to make a well prediction of the device non-linear characteristics. Besides the fundamental requirements of the well-matched dc, small signal characteristics and power performance provided by this model, a strict and accurate estimation of microwave non-linear power behavior especially under a digital modulation operation is also included. In this report, not only device microwave load-pull test has been described, the output spectra of the device under a digitally modulated scheme can be also predicted by this model, including the spectra regrowth and adjacent-channel power ratio. (C) 2003 Elsevier Science Ltd. All rights reserved.