High efficiency Doherty amplifier combining digital adaptive power distribution and dynamic phase alignment

This paper reports a Doherty power amplifier (PA) with significantly improved efficiency over large output power range. The efficiency enhancement is accomplished by associating digital adaptive power distribution and dynamic phase alignment mechanisms, which are implemented to prevent the efficiency degradation due to the problems of input drive waste at back-off, power-dependent phase misalignment between carrier and peaking branches, and impaired load modulation behavior. The measured average efficiency of the proposed Doherty PA is 53% compared to 45% for a standard Doherty PA.