A Consistency Enhancement Technique for MIMO Power Amplifier Modules

Hybrid beamforming reduces the hardware complexity of massive multiple-input multiple-output (MIMO) systems. In this architecture, one digital chain must drive all the power amplifiers (PAs) in the subarray. However, differences in PAs lead to poor linearization of shared digital pre-distortion (DPD). Based on circuit mechanisms and model simulations of PAs, this article identifies one reason for differences in PAs. Fluctuations in the manufacturing process lead to changes in the matching network of PAs, and the transmission characteristics of the matching network affect the nonlinear behavior of PAs. In order to reduce the network differences of PAs at the circuit level and improve the consistency of nonlinear behavior, this article proposes a consistency improvement scheme for MIMO power amplifier (PA) modules. The scheme uses the tuned network to correct the differences in the matching network. To validate the scheme, seven PAs from the same batch are corrected by the tuned network. Before and after the correction, the other PAs are linearized by the DPD signal of one PA. The measured bandwidths include 10 MHz and 40 MHz, and the measured power ranges from saturated average power to back-off of 9 dB. The results show that the PAs corrected by the tuned network have a better consistency. The linearization ability of the shared DPD one-drive-multiple is improved. The adjacent channel power ratio (ACPR) improvement reaches 14 dB.