An envelope linearization algorithm for an open-loop multi-switcher envelope tracking power amplifier

A linearization algorithm for the envelope supply voltage waveform is proposed for an open-loop multi-switcher envelope tracking power amplifier (ETPA). To maintain the fidelity of the supply voltage, we develop a two-step method comprising “non-linear pre-emphasis” and “envelope memory polynomial digital predistortion”, where the captured supply voltage of an RFPA is used. An ETPA is demonstrated using a 45 V CMOS multi-switcher envelope modulator and a 2.14 GHz 30 W GaN RFPA. The measured envelope absolute RMS error and ACLR are improved to 1.3% and -45 dBc from 6.4% and - 36dBc, respectively, compared with conventional pre-emphasis.