Men Zhirong, Wang Pengbo, Li Chunsheng, Chen Jie, Liu Wei, Fang Yue
School of Electronic and Information Engineering, Beihang University, Beijing 100191, China.
Collaborative Innovation Center of Geospatial Technology, Wuhan 430079, China.
Sensors (Basel). 2017 Jul 25;17(8):1700. doi: 10.3390/s17081700.
Synthetic Aperture Radar (SAR) is a well-established and powerful imaging technique for acquiring high-spatial-resolution images of the Earth's surface. With the development of beam steering techniques, sliding spotlight and staring spotlight modes have been employed to support high-spatial-resolution applications. In addition to this strengthened high-spatial-resolution and wide-swath capability, high-temporal-resolution (short repeat-observation interval) represents a key capability for numerous applications. However, conventional SAR systems are limited in that the same patch can only be illuminated for several seconds within a single pass. This paper considers a novel high-squint-angle system intended to acquire high-spatial-resolution spaceborne SAR images with repeat-observation intervals varying from tens of seconds to several minutes within a single pass. However, an exponentially increased range cell migration would arise and lead to a conflict between the receive window and 'blind ranges'. An efficient data acquisition technique for high-temporal-resolution, high-spatial-resolution and high-squint-angle spaceborne SAR, in which the pulse repetition frequency (PRF) is continuously varied according to the changing slant range, is presented in this paper. This technique allows echo data to remain in the receive window instead of conflicting with the transmitted pulse or nadir echo. Considering the precision of hardware, a compromise and practical strategy is also proposed. Furthermore, a detailed performance analysis of range ambiguities is provided with respect to parameters of TerraSAR-X. For strong point-like targets, the range ambiguity of this technique would be better than that of uniform PRF technique. For this innovative technique, a resampling strategy and modified imaging algorithm have been developed to handle the non-uniformly sampled echo data. Simulations are performed to validate the efficiency of the proposed technique and the associated imaging algorithm.
合成孔径雷达（SAR）是一种成熟且强大的成像技术，用于获取地球表面的高空间分辨率图像。随着波束控制技术的发展，滑动聚光灯和凝视聚光灯模式已被用于支持高空间分辨率应用。除了这种增强的高空间分辨率和宽测绘带能力外，高时间分辨率（短重复观测间隔）是众多应用的一项关键能力。然而，传统SAR系统的局限性在于，在单次飞行中，同一区域只能被照射几秒钟。本文考虑了一种新型的高斜视系统，旨在单次飞行中以从几十秒到几分钟不等的重复观测间隔获取高空间分辨率的星载SAR图像。然而，会出现距离单元徙动呈指数增加的情况，并导致接收窗口与“盲距”之间产生冲突。本文提出了一种用于高时间分辨率、高空间分辨率和高斜视角星载SAR的高效数据采集技术，其中脉冲重复频率（PRF）根据斜距的变化而连续变化。该技术可使回波数据保留在接收窗口内，而不会与发射脉冲或天底回波发生冲突。考虑到硬件精度，还提出了一种折衷且实用的策略。此外，针对TerraSAR-X的参数，对距离模糊度进行了详细的性能分析。对于强点状目标，该技术的距离模糊度将优于均匀PRF技术。对于这种创新技术，已开发出一种重采样策略和改进的成像算法来处理非均匀采样的回波数据。进行了仿真以验证所提技术及相关成像算法的有效性。
