Ambiguity Resolving and Imaging Algorithm for Multi-channel Forward-looking Synthetic Aperture Radar
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摘要: 传统合成孔径雷达方位向分辨率仅由合成孔径提供，但在正前视区域多普勒分集有限，成像性能迅速下降且前视成像也存在固有的左右多普勒模糊问题。针对上述问题该文讨论前视多通道合成孔径雷达系统模型，提出一种理想直线航迹下空域零点约束自适应波束形成的成像方法，有效综合阵列实孔径和合成孔径提高正前视区域的成像质量，利用有限阵列空域自由度实现左右多普勒解模糊。首先对回波数据大前斜成像处理，得到左右模糊的图像，然后进行波束形成，将各通道图像加权并且相干累加，实现左右多普勒解模糊以及方位分辨率增强。仿真实验表明空域零点约束自适应波束形成的成像方法可对前视场景进行高分辨成像。Abstract: The azimuth resolution of traditional synthetic aperture radar is only provided by synthetic aperture. However, in the forward looking area, the Doppler diversity is limited, so the imaging performance declines rapidly. And forward looking imaging also has the Doppler ambiguity problem. In this paper, an adaptive beam forming method with spatial confinement under ideal line track is proposed. The imaging quality of the positive forward region is improved effectively by combining the array of real aperture and synthetic aperture, and the Doppler solution is blurred by using the array space domain. First, the echo data is processed by High Squint SAR imaging to obtain the blurred image. Then the beam-forming is performed, weighted and coherent accumulated with each channel image, so as to resolve Doppler ambiguity and enhance the azimuth resolution. Simulation confirms the validity of the proposed approach.
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Key words:
- SAR /
- Forward-looking imaging /
- Azimuth resolution /
- Doppler ambiguity /
- Beam forming
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表 1 仿真参数
参数 数值 参数 数值 载频Fc 30 GHz 脉冲重复频率PRF 8000 Hz 信号带宽B 55 MHz 波束方位宽度 8° 采样带宽Fs 64 MHz 波束俯仰宽度 22° 下压角 20° 场景中心斜距Rs 7000 m 合成孔径长度 100 m 阵列实孔径长度 0.4 m 
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表 2 各方位点目标仿真分辨率与理论分辨率对比
参数 数值 数值 数值 数值 数值 坐标 (R0, 3.4°) (R0, –3.0°) (R0, 2.6°) (R0, 2.2°) (R0, 1.8°) 仿真分辨率IRW(rad) 6.76E–04 7.63E–04 8.72E–04 1.13E–03 1.53E–03 理论全孔径分辨率(rad) 7.00E–04 7.91E–04 9.09E–04 1.07E–03 1.29E–03 理论合成孔径分辨率(rad) 7.50E–04 8.55E–04 9.94E–04 1.19E–03 1.46E–03
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