Digital Predistortion of 5G Massive MIMO Wireless Transmitters Based on Indirect Identification of Power Amplifier Behavior With OTA Tests

In this article, we present a novel digital predistortion (DPD) architecture for multiple-input-multiple-output (MIMO) transmitters using a real-time single-channel over-the-air (OTA) data acquisition loop. The proposed feedback data acquisition strategy captures OTA signals from a fixed location and indirectly identifies the nonlinear behavior of all power amplifiers (PAs) in the array, as well as their combined signals in the far-field direction. The DPD can, therefore, be effectively constructed without direct measurement at PA output or at user end. The proposed linearization solution can run in real-time and, thus, does not interfere with data transmission in the MIMO transmitters. It can also achieve robust performance when mutual coupling occurs between antenna elements. Simulation and experimental results demonstrate that the proposed scheme can accurately estimate both PA outputs and far-field main beam data. Excellent linearization performance can be achieved with low complexity hardware implementation and reduced computational complexity.