Single-Receiver Over-the-Air Digital Predistortion for Massive MIMO Transmitters With Antenna Crosstalk

In this article, a novel digital predistortion (DPD) technique considering antenna crosstalk and using over-the-air (OTA) measurements is proposed for massive multiple-input multiple-output (mMIMO) transmitters. In the proposed DPD for hybrid beamforming with regular matrix array, all subarrays share an integrated linear crosstalk model (ICTM) block, a signal decomposition (SD) block, and a single receiver (SR) to reduce hardware complexity and cost greatly. Subarray coupling coefficients can be identified for the ICTM block without direct measurements. Using the SD block, receiving-end signals can be distinguished as feedback signals for each subarray from one feedback signal from SR. The receiving-end signals for each subarray can be linearized by a modified dual-input predistorter as per the distinguished feedback signals. For the special case of fully digital beamforming, the proposed DPD is the same as for hybrid beamforming. Simulation of eight-subarray hybrid beamforming transmitter is given to validate how the proposed DPD scales to mMIMO scenarios. Experimental results of three-subarray hybrid beamforming transmitter are provided, which indicate that the proposed DPD can achieve the similar linearization performance with less complexity, compared with the state-of-the-art dual-input with crosstalk and mismatch model (DI-CTMM) DPD.