Improving Near-Field Beamfocusing Effect via Array Manifold Optimization

This paper investigates the array manifold optimization to enhance the beamfocusing performance in near-field multi-user communications. We focus on the scenario where users are distributed at the same angle but different distances from the base station (BS). By analyzing the mutual coherence of near-field steering vectors, we propose a non-uniform linear array (NULA) configuration that effectively decorrelates users' spatial channels. Both theoretical analysis and numerical results demonstrate that the proposed NULA outperforms the sparse ULA with the same aperture size and the same number of antennas.