Forward Modeling Assisted Digital Predistortion Method for Hybrid Beamforming Transmitters with a Single PA Feedback

Abstract

This paper presents a novel forward modeling digital predistortion (DPD) method for hybrid beamforming transmitters based on a single power amplifier (PA) feedback. In hybrid beamforming transmitters, when multiple data streams are transmitted simultaneously, implementing DPD requires that all the PA’s outputs are sampled and divided into multiple data streams, which costs large hardware resources when there are massive antennas. However, generally, the PAs’ behavioral characteristics in beamforming transmitters are very similar, so the proposed method needs only one PA’s output in the feedback path to forward model all the PAs. Then all the PAs’ outputs can be estimated and used to extract DPD coefficients in digital domain. Compared with the DPD method that needs all the PA’s feedbacks of a hybrid beamforming transmitter, the proposed method can realize equivalent linearization performance while reducing PAs’ feedbacks significantly. The robustness of the proposed method is also validated by simulation. Compared with the existing single PA feedback DPD method, the proposed method can be also implemented even when multiple signals are in the same frequency band and it can thus enhance spectrum efficiency.