The target on the sea destroys the movement of the sea and affects an area around the target. Therefore, radar echoes from a target on the sea can be found in several successive range cells. Analysis of the echoes shows that the echoes of the target have a long range correlation in space. In this paper, we propose a target detection method by using the joint space-time-frequency decomposition, according to the diffidence between the target echoes and the sea clutter. Therein, the cross S-Method is proposed, which can be considered as the summation of the cross Wigner-Ville representations of the signal components and the sea clutter components, respectively. By using the inverse transform of the cross Wigner-Ville representation, we decompose the echoes from successive range cells. Then a signature, revealing the cross time-frequency concentration, is used to find the signal component in the decomposed signal components. The proposed method is evaluated by the X-band sea echoes with a simulated target or a real target. Results demonstrate that the proposed method not only detects the weak target in high accuracy, but also provides its instantaneous state.%海面目标不仅影响其位置处波浪运动，还会影响其周围的水域，其雷达回波信号分布于多个相邻的距离单元，所以目标回波信号表现出明显的空域相关性。该文根据海面目标信号的空间相关性提出了一种基于空域联合时频分解的海面微弱目标检测方法。该文提出的一种两信号互S-方法将相邻两个距离单元的回波信号变换到时频域，再利用互维格纳-威尔逆变换实现两距离单元信号的联合时频分解，最后根据分解分量的联合时频聚集性实现目标检测。实测X波段雷达海面回波的处理结果表明该文方法能够较精确地从海面回波中检测出微弱目标，并且能够显示目标的瞬时运动特性。
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