High-Efficiency Dual-Band Balanced-to-Doherty Mode-Switchable Power Amplifier With Large Frequency Ratio

This article presents a design method of dual-band power amplifier (PA) with switchable balanced and Doherty modes to obtain a mismatch resilience and a larger concurrent power. By designing the dual-band load-modulated network (DB-LMN) with a switchable load, balanced and Doherty mode reconfiguration is realized in dual band with a large frequency ratio. Meanwhile, to obtain the high efficiency for both modes, the dual-band matching network consisting of a harmonic control network (HCN), a two-section matching network, and an offset line is proposed. In addition, the proposed two-section matching network achieves dual-band matching with a large frequency ratio in a simple structure. Based on the proposed method, 0.9-/2.35-GHz PA with switchable balanced and Doherty modes was designed and measured. Under the continuous-wave stimulation, the 6-dB back-off and saturation efficiency of Doherty mode, and the saturation efficiency of balanced mode are 55%/47%, 73.1%/70%, and 71%/69%, respectively, at 0.9/2.35 GHz. Using a 10-MHz long-term evolution (LTE) modulated signal with 6-dB peak-to-average power ratio (PAPR), the measured average efficiency at the Doherty mode is 55%/49.5%, and the adjacent channel power ratio is better than - 29 dBc at operating frequencies. The measured results show that the proposed dual-band PA achieves an increase in saturated power up to 0.8/1.3 dB at 0.9/2.35 GHz under mismatched load conditions on the 2:1 voltage standing wave ratio (VSWR) circle. The concurrent output power can be improved by 1.5 dB by switching to the balanced amplifier (BA) mode.