New Digital Predistortion Training Method with Cross-Polarization Channel De-Embedding for Linearizing Dual-Polarized Arrays using Far-Field Observation Receiver

This paper proposes a far-field (FF) -based digital predistortion (DPD) training method for linearizing dual-polarized (dual-pol) beamforming arrays in the presence of cross-polarization channel (XPC) interference experienced in the DPD FF observation receiver (OR). The cross-polarization interference (XPI) in the XPC can be attributed to the transmitter’s antennas, the probe used in the DPD FF OR, the OR’s OTA channel, as well as the mechanical misalignment between the TX antenna and the FF OR probe. Specifically, an XPI estimation and de-embedding technique that corrects for both XPC errors using interleaved multi-tone test signals is proposed. Experiments conducted using a 4x4 dual-pol RF beamforming array operated at 38 GHz and excited by a 5G NR 200 MHz 256-QAM OFDM test signal are presented. The measurement revealed the capacity of the proposed technique to correct for the nonidealities in the XPC where the XPI was reduced from -10 dB to -40 dB.