Near-Field Beamforming Method for Distributed Array Radar Based on Nonuniform Range Segmentation and Steering Vector Cone Constraint

Distributed array radar (DAR) can improve the mainlobe jamming suppression ability by expanding the aperture of monostatic radar. However, traditional beamforming methods cannot accurately match the range parameter of steering vector and results in a performance degradation in the near-field applications of DAR. To address this issue, this paper proposes a near-field beamforming method for DAR based on non-uniform range segmentation and steering vector cone constraint. First, the proposed method divides the received signal into non-uniform range segments based on the criterion of maximum phase difference between subarrays. The non-uniform range segmentation reduces the near-field steering vector error within each range segment, thus prevents beam pattern distortion. Second, the method constructs a cone constraint that synchronously constrains the mainlobe and the range segment. Eigenvectors that meet the constraints are blocked by the eigen-projection matrix preprocessing (EMP) beamforming. By employing the cone constraint, the mainlobe within range segments can be maintained and residual jamming issues in certain range segments are avoided. Simulation and experimental results show that the proposed mainlobe jamming suppression beamforming method offers superior performance and lower hyperparameter dependence.