Digital Predistortion for Dual-Linearly Polarized Millimeter-Wave Phased Array User Equipment

To accommodate the ongoing user’s data explosion, many approaches like polarization multiplexing are proposed to increase the uplink communication capacity with limited bandwidth in user equipment (UE). This article proposes a novel dual-linearly polarized digital predistortion (DLP-DPD) scheme for DLP millimeter-wave (mmWave) phased array UE. Different from conventional single-polarized arrays, the DPD here not only aims to deal with the nonlinear distortion caused by power amplifiers (PAs) but also the cross-polarization interference which is a specific distortion in DLP phased array system. Theoretical analysis and system modeling of DLP phased array is presented, and a DLP-DPD model is proposed according to the derivation. Furthermore, in order to reduce the complexity of the DPD module, the proposed DLP-DPD scheme only needs to update a small part of coefficients when the user moves within a beam coverage. To validate the proposed DLP-DPD scheme, experiments were carried out on a 1 $\times $ 4 DLP mmWave phased array at 26.5 GHz. The experimental results show that DLP-DPD scheme can achieve good performance in DLP phased array dynamic scenario, dealing with the nonlinearity and cross-polarization interference well.