太赫兹视频SAR多普勒中心估计方法

受外界因素影响，机载合成孔径雷达(SAR)的飞行航迹与理想状态相比往往存在偏差，同时平台导航系统精确度有限，故需要从回波数据中精确估计多普勒中心频率，从而进行距离走动校正。多普勒中心估计误差决定了距离走动的校正精确度，从而决定了合成孔径成像方位压缩效果，是影响SAR成像质量的关键。在机载太赫兹成像雷达系统中，对运动补偿精确度的要求达到了亚毫米级，从而对多普勒中心估计误差提出了更高的要求。传统的多普勒中心估计方法在正侧视或小斜视模式下具有良好的效果，但在具有一定斜视角的模式下往往偏差较大。为了在多模式下有效完成太赫兹视频SAR距离走动校正，本文基于实测数据结果，从传统的包络估计方法出发，探究了一种改进包络估计的多普勒中心估计方法。通过比较，本文所提出的改进包络估计方法在对太赫兹视频SAR正侧视模式回波数据的多普勒中心估计上与另外两种传统方法都具有很高精确度，但在本文所提方法扫描模式下对97%的图像都作出了较为精确的估计，精确度与鲁棒性明显高于另外两种传统方法。结果说明了本文所提出的多普勒中心估计方法具有更好的鲁棒性、更高的效率。这一工作有助于高频段SAR多模式下的成像研究。

Doppler centroid frequency estimation method based on THz video-SAR

Affected by external environment, flight path of airborne Synthetic Aperture Radar(SAR) is always inaccurate. Under the circumstance of limited accuracy of navigation system, estimation of Doppler centroid frequency from airborne SAR data is necessary. Error of Doppler centroid frequency estimation decides the linear phase error, affects the estimation of high order phase error and azimuth compression quality. In airborne terahertz video-SAR system, submillimeter motion compensation accuracy is required, which tremendously increases the importance of Doppler centroid frequency estimation. Traditional Doppler center frequency estimation methods usually have good results in the frontal view or small squint mode of SAR system, but the deviation is often large in the mode of high squint angle. In order to effectively complete range walk correction in multiple modes, based on the measured data of THz video-SAR and starting from traditional envelope estimation method, an improved envelope estimation method is promoted. Compared with two traditional methods, in front view mode, all methods mentioned can give good results, but in scan SAR mode, 97% images can be well-estimated and focused with promoted method better than with other methods. By comparison, the proposed method exhibits higher robustness and efficiency. This work can help research on SAR imaging under high frequency.