Supply Modulation of a Linear Doherty Power Amplifier

This paper presents a study of supply modulation of a Doherty power amplifier (DPA) designed for linear operation. The symmetrical DPA is designed with Wolfspeed 6-W packaged devices for operation at 3.5 GHz with a peak output power of 42dBm and a peak power-added efficiency (PAE) of 55%. Supply modulation is characterized statically when the main and auxiliary amplifier supply voltages are modulated separately, as well as simultaneously. The DPA is then characterized with 60-MHz LTE-like signals with 6 dB and 10 dB peak-to-average power ratios (PAPR). After digital pre-distortion using an iterative learning control algorithm, the composite PAE for a 10-dB PAPR signal is 38.7%, with mean-square error (NMSE) and ACLR values of 0.3% and -47 dBc.