Adaptive Subarray Digital Beamforming with Robust Mainlobe Maintenance for Monopulse Angle Estimation in Complicated Jamming Environments

Existing digital array radars face significant challenges when dealing with simultaneous mainlobe and sidelobe jamming, particularly in large-scale phased arrays where element-level digital beamforming imposes high computational demands. To address these issues, this paper proposes an enhanced subarray adaptive processing architecture. A novel robust mainlobe maintenance technique, based on reconstructing the subarray interference and noise covariance matrix, is introduced to suppress multiple sidelobe jammers while preserving the shape and gain of the mainlobe. Subsequently, subarray sumdelta beams with maintained mainlobe are formed to mitigate mainlobe jamming. Finally, full-array adaptive sum-delta beams are employed for accurate monopulse angle estimation. Comprehensive simulation results demonstrate the proposed method's effectiveness in maintaining the mainlobe, canceling jammers, and achieving precise angle estimation, all with relatively low computational complexity.