基于流形滤波的海面微弱目标检测方法

Maritime Weak Target Detection Method Based on Manifold Filter

由于海面波动等因素近海杂波呈现出较强的非均匀特性,杂波功率估计误差较大,降低了海面微弱目标检测性能。针对这一问题,本文提出一种基于流形滤波的海面微弱目标检测方法,通过建立雷达回波信号的高维流形表示,将雷达目标检测问题转化为流形上两点间的区分性问题,同时,在流形空间中对杂波进行加权滤波处理,降低非均匀杂波能量,提高杂波功率估计精度,从而有效改善目标检测性能。首先,将每个距离单元的脉冲串回波数据建模为一个托普利兹正定矩阵,观测区域内各距离单元所对应的正定矩阵构成一个矩阵流形,杂波非均匀特性表现为矩阵流形上数据的几何拓扑性质;然后,通过在流形上聚类将非均匀杂波数据分解为若干类具有相似统计特性的数据,并估计每类杂波数据的几何中心;最后,针对不同类别的杂波几何中心在流形上进行加权滤波处理,提高非均匀杂波功率估计准确度,并设计相应的几何检测器。仿真和实测数据实验结果表明,所提方法能够提高非均匀海杂波的功率估计精度,改善微弱目标的检测性能。

Waves cause constant changes in the signal power of sea clutter,which demonstrates obvious nonhomogeneous characteristics.The detection performance for maritime weak targets is seriously restricted owing to the reduced estimation accuracy of clutter.To solve this problem,many detection algorithms have been designed to improve the sea-clutter detection performance.The information geometry detector,which maps the received signals to a matrix manifold and makes decisions based on the geometric distance in the manifold space,has shown great advantages in weak-target detection.However,its performance still suffers from the poor estimation accuracy of the clutter covariance matrix.To further improve the performance of the information geometry detector in sea-clutter environments,a maritime weak target detection method based on a manifold filter is proposed herein.First,the signals of the range cells were modeled as Toeplitz positive definite matrices,forming a matrix manifold.Each range cell corresponded to a point on the manifold,and the characteristics of the sea clutter could be expressed by the geometric topology characteristics of the manifold.Specifically,the points of range cells with similar statistical characteristics were closer on the manifold,while the nonhomogeneous points were separated.Next,considering the geometric structure of the manifold space,a clustering method was proposed for the manifold.A nonhomogeneous clutter was divided into several types of clutter with similar characteristics using this clustering method,and the geometric centers of these kinds were estimated.Because the clutter in a class demonstrated closer geometric distances,it was appropriate to use their geometric centers to represent the geometric distributions of these classes.Finally,based on the number of samples contained in each class,the weights of each clutter class were calculated to reduce the influence of nonhomogeneous clutter.Then,the manifold filter was used for different types of clutter to improve the estimate accuracy of the clutter covariance matrix.Experiments based on both simulated and measured data were conducted to analyze the performance of the proposed method and compared methods under different scenarios.The results showed that the proposed method could effectively improve the detection performance for maritime weak targets in sea-clutter environments.