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A three-way saturated Doherty power amplifier (S-DPA) based on class-F topology is proposed to improve efficiency at large backed-off output power regions. The high efficiency is demonstrated by implementing the amplifier using Eudyna EGN010MK GaN HEMTs and testing it with a continuous wave (CW) signal and a forward-link wide-band code division multiple access (WCDMA) 1-FA signal at 2.14 GHz. The proposed S-DPA has a power-added efficiency (PAE) of 50% for the CW signal at 10 dB backed-off output power region, while a two-way S-DPA and class-F PA have PAEs of 39% and 25%, respectively. Also, the proposed S-DPA has a PAE of 46.7% for the WCDMA 1-FA signal with peak-to-average power ratio of 10 dB, while the two-way S-DPA and the class-F PA have PAEs of 42.7% and 28.7%, respectively. Moreover, the proposed S-DPA, when linearized by a digital feedback predistorter, delivers an adjacent channel leakage ratio of 49.2 dBc at a 2.5 MHz offset with a PAE of 45.9%.
Date of Publication: Aug. 2008