Doherty Power Amplifier With Enhanced Efficiency at Extended Operating Average Power Levels

This paper proposes an electronically reconfigurable Doherty amplifier capable of efficiently amplifying wireless signals with significant time varying average power. This paper outlines closed-form equations used to design an effective Doherty amplifier that can be driven with signals of variable power levels using a small number of electronically tunable devices. As a proof of concept, a reconfigurable Doherty amplifier prototype was designed and fabricated that efficiently amplified signals centered at 2.6 GHz with output average power levels equal to 35, 30, and 25 dBm. The measurement results obtained using continuous wave signals revealed power-added efficiencies of greater than 66%, at input power level adjustments of 21 and 16 dBm, and more than 62% when the average input power level setting was adjusted to 11 dBm. In addition, the reconfigurable Doherty amplifier, driven with a 20-MHz long-term evolution signal, was successfully linearized using a pruned Volterra series based digital predistrtion algorithm.