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太赫兹条带SAR的PFA成像与误差补偿方法
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Abstract:
由于成像分辨率高、成像帧频高等优势，太赫兹合成孔径雷达(Synthetic Aperture Radar, SAR)正日益受到广泛的关注。而太赫兹波束窄使得其成像幅宽相对较小，这也正好符合极坐标格式算法(Polar Format Algorithm, PFA)的应用场景。然而PFA是针对聚束SAR成像的，不能直接应用于条带SAR；同时随着太赫兹SAR分辨率的提升，PFA对运动误差的二维空变影响无法忽视。为解决以上问题，本文提出了一种太赫兹条带SAR的PFA成像与误差补偿方法。首先通过确定条带SAR与聚束SAR之间的补偿函数实现二者的等效转换，拓宽PFA的应用范围；其次在PFA处理前采用互相关方法进行运动误差的粗补偿以减小PFA对运动误差的二维耦合影响；最后在PFA之后采用最大对比度自聚焦算法进行运动误差精补偿来满足太赫兹SAR的成像要求。仿真实验结果验证了该方法的有效性和鲁棒性。
Due to its high imaging resolution and frame rate, terahertz (THz) synthetic aperture radar (SAR) is increasingly attracting widespread attention. The narrow beam of terahertz waves results in a relatively small imaging swath, which aligns well with the application scenario of the Polar Format Algorithm (PFA). However, PFA is designed for spotlight SAR imaging and cannot be directly applied to stripmap SAR; moreover, with the improvement of THz SAR resolution, the two-dimensional space-variant impact of motion errors by PFA cannot be ignored. To address these issues, this paper proposes a PFA imaging and error compensation method for THz stripmap SAR. Initially, by establishing a compensation function between stripmap SAR and spotlight SAR for an equivalent conversion, the application range of PFA is expanded. Subsequently, a cross-correlation method is used for coarse compensation of motion errors before PFA processing to reduce the two-dimensional coupling impact of PFA on motion errors. Finally, a maximum contrast autofocus algorithm is applied after PFA for fine compensation of motion errors to meet the imaging requirements of terahertz SAR. Simulation experimental results verify the effectiveness and robustness of this method.
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