A digital Doherty transmitter suitable for wireless infrastructure efficiency enhancement

Abstract

The present work proposes a digital Doherty power amplifier (PA) with improved efficiency performance. The efficiency enhancement is achieved by using a digital adaptive phase alignment mechanism that is implemented to address the problem of power-dependent phase imbalance between the carrier and peaking cells of gallium-nitride (GaN) Doherty PAs following the turn-on of the peaking cell. An average efficiency of 57% has been measured using a one-carrier Worldwide Interoperability for Microwave Access (WiMAX) signal with a peak-to-average power ratio of 7 dB. This corresponds to an improvement of 7% in average efficiency with no linearity degradation compared to a conventional single-input fully analog Doherty PA.