The azimuth multichannel synthetic aperture radar (SAR) system can meet the requirements of high resolution and wide swath (HRWS) simultaneously, which overcomes the constraint of the traditional single-channel SAR. However, for a moving target illuminated by the azimuth multichannel SAR system, its radial velocity will lead to ambiguous components and mislocation in the image. Therefore, the radial velocity estimation plays an important role in improving the image quality and moving target relocation, especially for large ships on the open sea. However, as the pulse repetition frequency of a single channel is less than the Doppler spectrum, the traditional velocity estimation methods working in the image domain are out of action. This article suggests an idea that the issue of velocity estimation is converted into that of the linear phase errors estimation combining the linear fitting method, and it is assumed that the target has been already detected before applying the velocity estimation algorithms. To estimate the linear phase errors, two algorithms operating in the Doppler domain are introduced and compared, namely the subspace-based method and the modified frequency correlation method. The advantages of the proposed approaches are free from iteration operation and high accuracy. Besides, the effectiveness of the methods is demonstrated via simulation data and GaoFen-3 real data from ultra-fine stripmap mode. Finally, this article analyzes the velocity estimation accuracy of the two methods and the influence of channel imbalance through substantial experiments.

中文翻译：

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方位角多通道SAR系统中公海船舶的径向速度估计

方位多通道合成孔径雷达（SAR）系统可以同时满足高分辨率和宽幅（HRWS）的要求，克服了传统单通道SAR的局限性。但是，对于由方位多通道SAR系统照明的运动目标，其径向速度将导致图像中的成分模糊和位置不正确。因此，径向速度估计在改善图像质量和移动目标重定位方面起着重要作用，特别是对于公海上的大型船舶而言。但是，由于单个通道的脉冲重复频率小于多普勒频谱，因此在图像域中工作的传统速度估计方法无法发挥作用。本文提出了一种想法，即将速度估计的问题转换为结合线性拟合方法的线性相位误差估计的问题，并假定在应用速度估计算法之前已经检测到目标。为了估计线性相位误差，引入并比较了在多普勒域中运行的两种算法，即基于子空间的方法和改进的频率相关方法。所提出的方法的优点是没有迭代操作和高精度。此外，通过仿真数据和超细带状图模式的高芬3实测数据，证明了该方法的有效性。最后，本文通过大量实验分析了两种方法的速度估计精度以及信道不平衡的影响。