A Doherty Power Amplifier Based on AM-AM/PM Cancellation Combining Network Synthesized by Back-Off Complex Load Impedance

Abstract

This letter proposes a general design method for a linear Doherty power amplifier (DPA). With this method, the expanded or compressed amplitude-to-amplitude (AM-AM) and amplitude-to-phase (AM-PM) distortions of carrier power amplifier (PA) can be canceled at different back-off complex load impedance. In this design, a linear DPA is designed at 3.0–3.5 GHz for the prototype characterization. The measurement results show that the gain compression and phase variation are controlled within 1.3 dB and 5.5°, respectively. Applying a 100 MHz 64-QAM signal with a 6-dB peak-to-average power ratio, without any additional linearization method, the adjacent channel power ratio (ACPR) is below −40 dBc, and the average drain efficiency (DE) is better than 41% at the average output power of 37 dBm when the carrier frequency is swept from 3.1 to 3.3 GHz.