Dual-Wideband Three-Stage Doherty Power Amplifier Using Reciprocal Bias Configuration

This article presents an innovative power amplifier (PA) architecture designed to achieve dual-mode three-stage Doherty operation through the incorporation of a reciprocal bias configuration. A modified three-stage load modulation network (LMN) is proposed with the objective of simultaneously achieving an extended high-efficiency range and dual-wideband performance. Furthermore, a detailed account of the relevant three-stage Doherty load modulation process is provided, accompanied by a theoretical bandwidth analysis. To validate the proposed architecture and design method, a three-stage Doherty PA (DPA) prototype employing commercial gallium nitride (GaN) active devices has been designed and meticulously fabricated. The prototype exhibits a bandwidth of 1.0–1.7 GHz in Mode I and 0.5–0.9 GHz in Mode II, thereby corroborating the efficacy of the proposed approach. The fabricated three-stage DPA achieves a peak output power of 43.6–44.6 dBm across the two designated bands. The drain efficiency was found to be between 41.5% and 51.6% and between 44.0% and 58.0% at 9–10-dB output power back-off (OBO) in Mode I and Mode II, respectively. When driven by a 10-MHz 64QAM signal with a 9-dB peak-to-average power ratio (PAPR), an average efficiency exceeding 40% was achieved.