Analysis and Design of Reconfigurable Multiband Mismatch-Resilient Quasi-Balanced Doherty Power Amplifier for Massive MIMO Systems
Haifeng Lyu, Kenle Chen
Abstract
A novel power amplifier (PA) with wide bandwidth and load mismatch resilience is presented based on the quasi-balanced Doherty PA (QB-DPA) architecture. By reconfiguring the parallel/series QB-DPA operation modes with the nominal/exchanged biasing alternation and control of phase dispersion, the proposed QB-DPA topology can overcome the bandwidth limitations and ensure a standard Doherty profile and high efficiency and linearity against dynamic load mismatch over the operational bandwidth. Based on the theoretical analysis, a design guidance of output matching topology on phase offset implementation is presented. As a proof of concept, a physical prototype is demonstrated targeting for 1.7–2.7-GHz bandwidth. The developed QB-DPA achieves an efficiency of 56%–78% at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {OP}_{\mathrm {1\,dB}}$ </tex-math></inline-formula> and 47%–71% at 6-dB output back-off (OBO) over the in-band operation with 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> load. Through reconfiguration (parallel/series mode for mismatch recovery and nominal/exchanged biasing for bandwidth extension), the developed QB-DPA demonstrates significantly improved <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {OP}_{\mathrm {1\,dB}}$ </tex-math></inline-formula> variation both at center frequency 2.1 GHz and edged-frequency 1.7 and 2.6 GHz at 2:1 voltage standing wave ratio (VSWR) over 360° phase span. In modulated measurement using 20-MHz long-term evolution (LTE) signals, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$> 44.5\%$ </tex-math></inline-formula> average efficiency and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ < -30.9$ </tex-math></inline-formula> -dBc adjacent channel power ratio (ACPR) are obtained across the wide bandwidth at matched-load condition. More importantly, for VSWR 2:1 circle, the high linearity [ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ < 5.3\%$ </tex-math></inline-formula> error vector magnitude (EVM)] and average efficiency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$> 38.1\%$ </tex-math></inline-formula> ) can be experimentally maintained through reconfigurations.