A Reconfigurable Hybrid Series/Parallel Doherty Power Amplifier With Antenna VSWR Resilient Performance for MIMO Arrays Naga Sasikanth Mannem , Student Member , IEEE, Min-Y u Huang , Member , IEEE, Tzu-Y

Abstract

Antenna load impedance variations typically cause significant power amplifier (PA) performance degradation, including output power, large-signal linearity, and peak/average PA efficiency, which are especially critical for modern millimeter- wave (mm-Wave) communications with spectrally efficient complex modulations. To address this problem, we propose a reconfigurable hybrid series/parallel Doherty PA with a 90 ◦- coupler-based active load modulation network. By reconfiguring the series/parallel Doherty operation modes, the strengths of the Main/Auxiliary PAs, and their relative phase, linear output power (OP 1d B ), as well as peak output power ( Psat) and energy efficiency (PAEpeak and PAE1d B ) of the PA can be largely restored under full-span 360◦ antenna impedance variations. The theoret- ical analysis and design guidelines are both presented in this article. As a proof of concept, a 39-GHz reconfigurable hybrid series/parallel Doherty PA is fabricated in the Global Foundries 45-nm RF CMOS silicon on insulator (SOI) process with a 2-V PA supply and 1-V driver supply. At 39 GHz, the PA achieves a 33.3% peak power-added efficiency (PAE) at 20.8-dBm P sat and 32.2% PAE1d B at 20.2-dBm OP 1d B at a nominal 50- /Omega1load. The reconfigured PA demonstrates an 18.5–19.12-dBm OP 1d B with a high PAE1d B of 20.6%–25.3% at 3:1 antenna voltage standing wave ratio (VSWR) over 360 ◦ angles. The PA achieves an rms error vector magnitude (EVM) of −23.6 dB/−22.8 dB/−23.1 dB at an average Pout of