Near-Field Wideband Beamfocusing Optimization: A Heuristic Two-Stage Approach

Abstract

A near-field wideband multi-user communication system is studied. To eliminate the near-field beam split caused by the wideband spatial effect, a hybrid beamforming architecture based on true-time delayers (TTDs) is exploited. A heuristic two-stage approach is proposed for optimizing the analog and digital beamformers of the TTD-based hybrid beamforming architecture to facilitate near-field wideband beamfocusing. In particular, in the first stage, a closed-form analog beamformer design based on a piecewise-near-field approximation is proposed to maximize the array gain at users. Next, in the second stage, the digital beamformers are optimized by exploiting the successive convex approximation. Finally, our numerical results demonstrate that the proposed approach can effectively eliminate the near-field beam split and outperforms the existing approach in terms of spectral efficiency.