Wideband phase inverter integrated in Doherty power amplifier for linearity improvement

A wideband phase inverter (WPI) integerated in a Doherty power amplifier (DPA) is proposed for linearity improvement. This WPI is integrated at the output of the carrier amplifier in the DPA while keeping the same size as the conventional DPA. The input signal is excited at both the carrier and the peaking amplifiers and then the amplified signals are combined by the push-pull toplogy. This results in the cancellation of the even-order harmonic terms as well as the cancellation of IMD3 by proper bias selection. An experiment shows the peak power-added efficiency (PAE) is around 50% at 21 dBm output power with linearity improvement as the adjacent channel leakage ratio (ACLR) under a wideband code division multiple access signal is around-40 dBc. This improves around 7 dB in ACLR under the same output power and PAE and better error vector magnitude (EVM) compared with the single-stage class AB amplifier. Copyright © 2015 The Institution of Engineering and Technology.