Analysis and Design of Reconfigurable Multiband Mismatch-Resilient Quasi-Balanced Doherty Power Amplifier for Massive MIMO Systems

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
$\text {OP}_{\mathrm {1\,dB}}$
and 47%–71% at 6-dB output back-off (OBO) over the in-band operation with 50-
$\Omega $
load. Through reconfiguration (parallel/series mode for mismatch recovery and nominal/exchanged biasing for bandwidth extension), the developed QB-DPA demonstrates significantly improved
$\text {OP}_{\mathrm {1\,dB}}$
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,
$> 44.5\%$
average efficiency and
$ < -30.9$
-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 [
$ < 5.3\%$
error vector magnitude (EVM)] and average efficiency (
$> 38.1\%$
) can be experimentally maintained through reconfigurations.