Off-Grid Angle-Doppler Estimation for Space-Time Adaptive Processing: A Sequential Approach

The accuracy and efficiency of angle-Doppler estimation are critical for space-time adaptive processing (STAP). These two demands, however, are usually contradictory. In this paper, we propose a sequential approach for off-grid angle-Doppler estimation in the framework of STAP, where both the accuracy and efficiency are well balanced. The sequential characteristic of the proposed algorithm can be reflected from two aspects. On one hand, the angle-Doppler estimation is accomplished via a two-stage procedure, where the coarse sparse reconstruction and the rotational invariant technique are sequentially incorporated. On the other hand. the closed-form solutions to off-grid angle and Doppler parameters are sequentially formulated, which are subsequently paired via an Euclidean distance minimization-based principle. Benefiting from such sequential implementation, the computational complexity can be greatly reduced, and the basis mismatch problem can be avoided in the meantime. Simulation results demonstrate the effectiveness of the proposed algorithm.