A Design Strategy for Linearity-Enhanced Doherty Power Amplifier by Input Harmonics Control

Abstract

In this letter, a linearity-enhanced Doherty power amplifier (DPA) design strategy based on input second-harmonics control is proposed. By combining the load modulation process and analyzing the gain compression and phase changes caused by introducing input harmonics, suitable harmonic parameters are determined. The proposed method helps to reduce amplitude-to-amplitude (AM-AM) and amplitude-to-phase (AM-PM) distortion. Moreover, this method has a minimal impact on efficiency. To verify this method, a linearity-enhanced DPA is designed to operate within 3.2–3.7 GHz. Test results exhibit AM-AM distortion within 0.75 dB, AM-PM distortion within 3°, and the adjacent channel power ratio (ACPR) better than −40 dBc under 80-MHz modulated signal excitation.