Design of Ultra-Wideband Doherty Power Amplifier Using a Modified Combiner Integrated with Complex Combining Impedance.

To be compatible with future wireless communication systems, it is very necessary to extend the bandwidth of the Doherty power amplifier (DPA). In this paper, a modified combiner integrated with a complex combining impedance is adopted to enable an ultra-wideband DPA. Meanwhile, a comprehensive analysis is performed on the proposed method. It is illustrated that the proposed design methodology can provide power amplifier (PA) designers with more freedom in implementing ultra-wideband DPAs. As a concept of proof, a DPA working over 1.2-2.8 GHz (a relative bandwidth of 80%) is designed, fabricated and measured in this work. Experimental results showed that the fabricated DPA delivers a saturation output power of 43.2-44.7 dBm with a gain of 5.2-8.6 dB. Meantime, the fabricated DPA achieves a saturation drain efficiency (DE) of 44.3-70.4% and a 6 dB back-off DE of 38.7-57.6%.