A microwave Doherty amplifier employing envelope tracking technique for high efficiency and linearity

Abstract

In this letter, we have demonstrated a microwave Doherty amplifier employing input signal envelope tracking technique. In the amplifier, gate bias of peaking amplifier is controlled according to the magnitude of the envelope. A 2.14-GHz Doherty amplifier has been implemented using 4-W PEP LDMOSFE'ts and an adaptive controlled gate bias circuit has been constructed and the control shape is optimized experimentally. The performance of, the, microwave Doherty amplifier has been compared with those of class AB amplifier using one-tone, two-tone, and forward-link wideband code-division multiple access (WCDMA) signals. For a forward-link WCDMA signal, the measured power added efficiency (PAE) of the microwave Doherty amplifier is 30.4% at -30 dBc adjacent channel leakage ratio (ACLR), while that of, the comparable class AB amplifier is 24.2% at the same. ACLR level.