Nonlinear dispersive effects modelling for the accurate drain current prediction in GaN-based microwave power amplifiers

A new approach is presented for the accurate modelling of the dynamic drain current in GaN-based FETs, accounting for both self-heating and charge-trapping phenomena. The dynamic nonlinearity of the trapping effects is here taken into account for the first time. The device internal state is found not only dependent on the mean values of the applied voltages (as in conventional approaches), but also on the AC voltage spectral components. This is particularly important in order to correctly predict the dependence of the drain current DC component on signal amplitude (i.e. AC to DC conversion) and, consequently, of the Power Added Efficiency. The model has been developed and identified for a medium-power GaN-based device. Experimental validation data show that significant improvement in the prediction of AC to DC conversion is obtained with respect to conventional models.