Distortion shaping in space and frequency using digital predistortion in MIMO transmitters

Artikel i vetenskaplig tidskrift, 2026

A novel approach to multiple-input, multiple-output transmitter distortion shaping that shapes emitted distortion at different frequencies, and in different spatial directions, differently is proposed. In this approach, a new criterion of optimality using weighted over-the-air observations, and a digital predistortion (DPD) scheme particularly adapted to this criterion, are formulated. Through simulation, it is shown that emitted in-band and out-of-band distortion can be shaped spatially in the proposed approach, with up to 8 dB in-band distortion reduction in a user direction, compared to conventional per-PA DPD.