Optimal Two-Way Hybrid Doherty-Outphasing Power Amplifier

Abstract

This paper presents a two-way hybrid Doherty-outphasing power amplifier (HD-OPA) with an optimal efficiency. The HD-OPA consists of a main PA operating in class-F and an auxiliary PA operating in class-C which jointly operate in the Doherty mode at lower power and the outphasing mode at higher power. The peak to backoff fundamental drain voltage ratio of the auxiliary PA is optimized such that the main and auxiliary transistors both deliver their maximum power at peak power. As a result, the outphasing angles between the two inputs need to be changed dynamically with the dual-input power level. This concept is validated by a fabricated 2.08 GHz PA demonstrator circuit with a drain efficiency of 71.1 % at 8 dB backoff power and a drain efficiency of 74.6 % at 45.1 dBm peak power in continuous-wave measurements. When excited with a 20-MHz LTE signal with 9.55 dB peak-to-average-power-ratio, the HD-OPA yields an average efficiency of 56.7 %, average power-added-efficiency of 52.3 % and adjacent-channel-leakage-ratio of -49.0 dBc after linearization.