A Compact Single Transformer Footprint Hybrid Current-Voltage Digital Doherty Power Amplifier

Abstract

This paper presents a fully integrated single footprint hybrid current-voltage mode digital Doherty power amplifier (PA). A prototype PA is implemented in a 45nm CMOS SOI process. The proposed PA design provides enhanced linearity through adaptive biasing-based AM-PM distortion mitigation of the current mode digital PA and AM-PM cancelation through hybrid current/voltage mode Doherty-based power combining. It achieves 21.7dBm peak output power $(\mathrm{P}_{\text{sat}})$ at 1.2GHz and 37.6% drain efficiency (DE) at 1.4GHz. The proposed digital Doherty PA demonstrates $1.2\times/1.22\times \text{PBO}$ efficiency enhancement, compared to the ideal class-B at 3/6 dB PBO at 1.2GHz. The measured error vector magnitude (EVM) of 64-QAM/20MHz is −23dB with 22.8% average DE without DPD. This is the first demonstration of hybrid current-voltage mode Doherty power combining on a single footprint transformer over a broad bandwidth (BW)