Abstract: This article presents a comprehensive theoretical analysis of the resilience demonstrated by the three-stage Doherty power amplifier (DPA) when operating under load mismatch conditions. Additionally, a novel reconfigurable three-stage DPA architecture is introduced, with the aim of enhancing resilience to load mismatch using exceptionally simple circuits and a one-dimensional (1D) control method. To validate the efficacy of this proposed architecture and control approach, a DPA prototype employing commercial gallium nitride (GaN) active devices has been designed and meticulously fabricated at 2 GHz. With a matched 50 Ω load, the fabricated three-stage DPA achieves a high-efficiency range of 9.5 dB with larger than 51% back-off drain efficiency (DE). Through the proposed 1D control, the DPA presents 47.0%–55.1% back-off efficiency with ≤ 2 dB power fluctuation at a 2:1 voltage standing wave ratio (VSWR) over a 360° phase span. When driven by a 20 MHz long-term evolution (LTE) signal with an 8 dB peak-to-average power ratio (PAPR), the DPA achieves 46.2%–53.9% average efficiency and better than -21 dBc adjacent channel power ratio (ACPR) without digital pre-distortion (DPD) under load mismatch conditions.

Key words: Doherty power amplifier; Load mismatch; One-dimensional (1D) control; Reconfigurable; Three-stage

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