Triple-Mode Reciprocal Doherty Power Amplifier With Multi-Band Operation and Extended High Efficiency Range
Shuang Liu, Jingzhou Pang, Ruibin Gao, Tingting Yao, Tianfu Cai, Mingyu Li, Weimin Shi, Zhijiang Dai
Abstract
This article presents the methodology for designing triple-mode Doherty power amplifier (DPA) with multi-band operation and extended high efficiency range. It is illustrated that three different Doherty operation modes can be realized by simply re-setting the gate bias voltages while the DPA circuits keep unchanged. By employing a novel reciprocal gate bias DPA architecture, five operation bands have been achieved by the proposed DPA with larger than 9 dB high efficiency power range. The active load modulation process and theoretical performance of proposed DPA are analyzed in detail for each mode. For verification, a commercial GaN transistors-based DPA is designed and implemented with 1.76–1.96 GHz band in Mode I, 1.13–1.20/2.48–2.58 GHz bands in Mode II and 0.7–0.76/2.34–2.40 GHz bands in Mode III. The fabricated DPA achieves 7.0–10.5 dB saturation gain, 44.18–46.86 dBm peak output power and 41.9%–61.5% back-off efficiency. When stimulated by a 10 MHz long term evolution (LTE) modulation signal with 8.6 dB peaking-to-average ratio (PAPR), the adjacent channel power ratio (ACPR) of the fabricated DPA is better than −45 dBc after digital pre-distortion at 0.73, 1.18 and 1.85 GHz.