Enhanced Class-A/AB mobile terminal power amplifier efficiency by input envelope injection and “self” envelope tracking

A baseband modulation technique is proposed to improve the efficiency and linearity of Class-A/AB radio frequency (RF) power amplifiers (PAs). The baseband load impedance is optimized, and the input envelope - along with the RF signal - is fed to the PA input. The resulting baseband modulation of the drain increases the saturated RF output power and improves the linearity for a given dc power consumption. A 2GHz HFET power amplifier exhibited a significant improvement in peak PAE from 40% to 54% for a two-tone input and from 23% to 27% for a 5MHz BW 64-QAM signal.