Waveform Synthesis for Active Loadpulling Mitigation in Multiuser MIMO Transmitters

The rapid development of massive multiple input and multiple output (m-MIMO) systems has raised the demand for higher antenna array integration, which introduces challenges related to antenna mutual coupling and the resulting power amplifier (PA) loadpulling effect. By ensuring uniform excitation magnitudes across all active RF chains, this paper proposes a method through constant envelope excitation across the transmit array that minimizes variance of the changes of the active impedance seen by each PA, thereby providing more consistent PA performance across the array and, thus, improving the network capacity. Simulation results demonstrate that, compared to the counterpart systems using traditional zero forcing (ZF) precoder, the proposed method significantly reduces the loadpulling effect.