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A New Approach to Range Cell Migration Correction for Ground Moving Targets in High-resolution SAR System Based on Parameter Estimation
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摘要: 距离徙动校正(RCMC)是机载单天线高分辨率合成孔径雷达(SAR)实现运动目标聚焦成像的关键环节。针对现有方法运算量大、精度低的缺点，该文提出一种结合参数估计分4步完成的RCMC方法。该方法首先通过结合能量均衡法的Hough变换估计距离向速度并校正距离走动，然后以初始方位向调频率校正距离弯曲，再采用Map-drift估计精确的方位向调频率，最后校正残余距离弯曲。与传统方法相比，该方法计算量较小，性能稳定，并能够校正高分辨率下不可忽略的残余距离弯曲。该文给出新方法的数学模型，并通过仿真和实际数据处理验证了该方法的有效性。Abstract: Range Cell Migration Correction (RCMC) represents an important advance in moving target imaging in the airborne single antenna high-resolution SAR system. In this paper, we propose a new four-step RCMC approach combined with parameter estimation that overcomes the drawbacks of high computation and low accuracy in high-resolution. First, we use the Hough transform and the energy balancing method to estimate the range velocity and correct the range walk. Next, we perform a range curvature correction in the range-Doppler domain by using the initial Doppler rate. Thirdly, we accurately estimate the Doppler rate using Map-drift technology. Finally, we correct the residual range curvature by the accurate Doppler rate. Compared with traditional algorithms, the proposed method requires less computation and is robust in the high-resolution SAR system. In this paper, we present a mathematical model and validate its effectiveness using both simulation and real data.
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图 8 结合能量均衡法的Hough变换结果
Figure 8. Results of Hough transform with energy balancing method
图 10 动目标精确成像并定位的合成SAR图像
Figure 10. Composite SAR image with stationary scenes and focused moving targets
表 1 雷达仿真参数
Table 1. Parameters of simulation
参数名称 参数值 距离向点数 2048 方位向点数 2048 中心频率(GHz) 15.6 距离向采样率(MHz) 750 信号带宽(MHz) 600 信号脉宽(μs) 1 飞机地速(m/s) 80 脉冲重复频率(Hz) 480 中心斜距(km) 5 
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表 2 目标仿真参数
Table 2. Parameters of simulated targets
目标编号 距离向速度
(m/s)方位向速度
(m/s)距离向加速度
(m/s2)目标1 –1 –1 0 目标2 10 10 0 目标3 10 10 –0.2
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表 3 距离向速度估计结果
Table 3. Estimation results of range velocity
目标编号 Hough变换估计结果(m/s) Hough变换估计相对误差(%) 本文算法估计结果(m/s) 本文算法估计相对误差(%) 目标1 0.13 113.00 –0.98 2.00 目标2 10.45 4.50 10.03 0.30 目标3 10.04 0.40 10.02 0.20
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表 4 方位向调频率估计结果
Table 4. Estimation results of azimuth frequency rate
目标编号 真实值(Hz/s) 本文算法估计
结果(Hz/s)本文算法估计
相对误差(%)目标1 137.88 138.03 0.11 目标2 101.92 102.11 0.19 目标3 80.09 80.22 0.16
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表 5 算法运算时间
Table 5. Execution time of traditional method and proposed method
算法类别 算法步骤 执行时间(s) 常规算法 Keystone变换 36.43 距离弯曲粗校正 0.18 总时间 36.61 本文算法 Hough变换 0.53 多普勒中心估计 0.11 距离走动校正 0.26 距离弯曲粗校正 0.18 Map-drift 0.75 距离弯曲精校正 0.18 总时间 2.01
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表 6 实测数据参数
Table 6. Parameters of real data
参数名称 参数值 距离向点数 800 方位向点数 32768 中心频率(GHz) 15.6 距离向采样率(MHz) 1000 信号带宽(MHz) 700 信号脉宽(μs) 60 飞机地速(m/s) 66 脉冲重复频率(Hz) 1200 中心斜距(km) 15
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