Two-dimension Space-variance Correction Approach for Diving Highly Squinted SAR Imaging with Sub-aperture
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摘要: 俯冲合成孔径雷达(SAR)常采用大斜视子孔径成像来满足平台机动性和处理实时性；而大斜视模式下距离方位的严重耦合、斜视角沿距离向的空变及3维速度和加速度的存在会导致距离包络和方位相位的2维空变，严重影响成像质量。针对这些问题，该文提出一种新的两级频域滤波算法，在预处理后，首先引入第1级频域滤波因子以校正距离包络沿方位位置的空变以实现距离徙动统一校正，然后采用第2级频域滤波校正方位多普勒参数的空变实现方位相位统一聚焦。仿真实验验证了该算法的有效性。Abstract: The diving SAR usually adopts the highly squinted mode and sub-aperture to satisfy the maneuvering and real-time processing. However, the existence of severe range-azimuth coupling, range-dependent squint angle and three-dimension velocity and acceleration leads to the space variance of range envelope and azimuth phase, which makes imagery unfocused seriously. To solve these problems, a Two-stage Frequency Filtering Algorithm (TsFFA) is proposed. After preprocessing, the First-stage Frequency Filtering (FsFF) factor is first introduced to correct azimuth-dependent Range Cell Migration (RCM) and realize the unified RCM correction. Furthermore, the Second-stage Frequency Filtering (SsFF) factor is adopted to equalize azimuth-dependent Doppler parameters and realize unified azimuth phase focused. Simulation results are presented to validate the effectiveness of the proposed approach.
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表 1 仿真参数
载频 15 GHz 脉冲重复频率 2.5 kHz 距离带宽 200 MHz 高度 5 km 脉冲宽度 10 μs 场景中心斜距 10 km 方位侧视角 28° 平台速度 (145, –38, –35) m/s 加速度 (1.2, 0.5, –0.8) m/s2 合成孔径时间 0.6 s 
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表 2 性能指标测量结果(未加窗)
性能指标 参考方法 本文方法 点1 点3 点5 点1 点3 点5 峰值旁瓣比(dB) –3.46 –13.23 –5.63 –13.23 –13.25 –13.21 积分旁瓣比(dB) –4.24 –9.77 –5.92 –9.77 –9.83 –9.76 方位分辨率(m) 1.58 1.05 1.46 1.03 1.01 1.04
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