基于自适应字典校正的稀疏恢复STAP算法
Sparse Recovery STAP Algorithm Based on Adaptive Dictionary Correction
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摘要: 空时自适应处理(Space-Time Adaptive Processing, STAP)技术在时间维(脉冲维)和空间维(阵元维)联合进行信号处理,以实现动目标检测功能。但是,传统STAP技术的计算复杂度非常高,而且在优化处理信号过程中需要大样本的支撑,在实际的工作场景中,杂波环境复杂易变,不易获取足够多的独立同分布样本,因此杂波抑制效果较差。稀疏恢复空时自适应处理(Sparse Recovery Space-Time Adaptive Processing, SR-STAP)算法可以利用很少的训练样本实现杂波抑制,但大多数SR-STAP算法的计算量巨大,运行速度慢,算法实时性不高。此外,SR-STAP算法需要对连续空时二维平面进行离散化处理,将空时二维平面划分为很多细小的网格,由于真实的杂波在空时平面上是连续分布的,同时考虑雷达接收信号中噪声、系统参数误差等因素的影响,真实杂波点与离散化网格点之间一定存在着偏差,会造成网格失配现象,导致SR-STAP算法杂波抑制性能下降。针对此问题,本文提出了基于自适应字典校正的稀疏恢复STAP算法。该算法首先通过子空间投影法筛选出与杂波最相关的原子;然后围绕选定原子由粗到细进行自适应局部网格划分,按照局部网格迭代选优准则,不断调整选择局域内的最优原子,直到满足迭代终止条件,以匹配真实的杂波点;最后利用选定的最优原子对应的空时导向矢量构造杂波子空间,更新噪声子空间上与杂波子空间正交的投影矩阵得到STAP权值。仿真实验表明,所提算法与传统SR-STAP算法相比,具有更高的稀疏恢复精度,更快的运行速度,改善了STAP性能。Abstract: The space-time adaptive processing (STAP) technology jointly performs signal processing in the time (pulse dimension) and space (array dimension) dimensions to realize the dynamic target detection function. However, the computational complexity of traditional STAP technology is substantial, and it needs the support of large samples when optimizing the signal processing. In real-world scenarios, the cluttered and changing environment complicates acquiring sufficient independent and identically distributed samples, resulting in suboptimal clutter suppression. Sparse recovery space-time adaptive processing (SR-STAP) algorithms are capable of achieving clutter suppression with a limited number of training samples. However, the majority of SR-STAP algorithms have considerable computational complexity, slow running speed, and low real-time performance. In addition, the SR-STAP algorithm needs to discretize the continuous space-time two-dimensional plane, and the space-time two-dimensional plane is divided into several small grids. The continuous distribution of real clutter across the space-time plane, coupled with noise and system parameter errors in radar signals, leads to discrepancies between actual clutter points and discretized grid points. This grid mismatch affects the clutter suppression performance of the SR-STAP algorithm. To address this issue, this paper proposes a dictionary mismatch correction SR-STAP algorithm based on local grid adaptive division. First, the algorithm selects the atoms that have the highest correlation with clutter using the subspace projection method. Subsequently, adaptive local grid division is performed around the selected atoms from coarse to fine. According to the local grid iterative optimization criterion, the optimal atoms in the local area are constantly adjusted and selected until the iteration termination condition is satisfied to match the real clutter points. Finally, the clutter subspace is constructed using the space-time steering vector corresponding to the selected optimal atom, and the STAP weight is obtained by updating the projection matrix orthogonal to the clutter subspace on the noise subspace. Simulation results show that, compared with the traditional SR-STAP algorithm, the proposed algorithm has higher sparse recovery accuracy, faster running speed, and improved STAP performance.