The Influence of the Azimuth RCS Pattern of Calibrator on SAR Absolute Calibration
The Influence of the Azimuth RCS Pattern of Calibrator on SAR Absolute Calibration
复制标题
定标器方位角RCS方向图对SAR绝对定标的影响
DOI：
10.1109/lgrs.2021.3120433
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发表时间：
2021-10
影响因子：
4.8
通讯作者：
Huang Jianjun
中科院分区：
文献类型：
--
作者：
Du Shaoyan;Hong Jun;Wang Yu;Xing Kaichu;Qiu Tian;Huang Jianjun
辐射定标的实现依赖于已知的人工点目标作为参考，如角反射器。校准器的标准之一是方位雷达截面（RCS）方向图的3dB波束宽度需要大于合成孔径雷达（SAR）天线的3dB波束宽度，以确保具有窄方位波束宽度的SAR天线能够对准校准器，同时还使得校准器的标称RCS值在辐射校准期间近似恒定。然而，校准器的RCS实际上是在合成孔径周期内不恒定的，特别是当SAR天线波束宽度较宽时。简化的处理会给校准带来误差。在这封信中，方位RCS图案被考虑在内。建立了恒定RCS引起的误差模型。在误差模型的基础上，讨论了一种改进的校准判据。利用已知的SAR系统参数，对不同尺寸的二面角反射器进行了数值模拟实验。仿真结果验证了误差模型的正确性，并指出当SAR波束宽度大于定标器波束宽度时，引入的误差不可忽略。通过实验进一步分析了定标器尺寸与SAR波束宽度的关系。
The realization of radiometric calibration relies on the known artificial point targets as the reference, such as corner reflectors. One of the criteria of the calibrator is that the 3 dB-beamwidth of the azimuth radar cross section (RCS) pattern needs to be larger than the synthetic aperture radar (SAR) antenna 3-dB beamwidth to ensure the SAR antenna, which has a narrow azimuth beamwidth, can align to the calibrator while also making the nominal RCS value of the calibrator approximately constant during the radiometric calibration. However, the RCS of the calibrator is actually inconstant within a synthetic aperture period, especially when the SAR antenna beamwidth is wide. The simplified treatment will introduce errors to calibration. In this letter, the azimuth RCS pattern is taken into account. The error caused by the constant RCS is modeled. Based on the error model, an improved criterion of the calibrator is discussed. The experiments use the known SAR system parameters for numerical simulation based on dihedral corner reflectors (DCRs) with different sizes. The results verify the error model and indicate that when the SAR beamwidth is larger than the beamwidth of the calibrator, and the introduced error cannot be ignored. The relationship between the size of the calibrator and the SAR beamwidth is further analyzed through the experiments.