A hybrid Cartesian loop and envelope modulated PA linear transmitter architecture

A high efficiency and linearity PA solution is presented based on hybrid linearisation schemes that employ complementary techniques to overcome the weakness (or constraints) of either method on its own. In particular, the high linearity of Cartesian loop is combined with the high efficiency of envelope elimination and restoration (EER). The results of a prototype hybrid linearised PA built using digital generation of the phase and amplitude signals for the EER amplifier, and utilizing a digital Cartesian feedback loop are presented. Limitations of the amplitude modulator on system performance are demonstrated using PWM and delta-modulated switching amplifiers.