低信杂噪比合成孔径雷达数据的预滤波处理

针对机载合成孔径雷达(synthetic aperture radar， SAR)中由于波束指向不准、不完全孔径效应以及内部噪声增大等因素所造成目标回波信杂噪比(signal to clutter noise ratio, SCNR)下降现象，本文提出一种对子孔径回波进行迭代变加载去除杂波噪声方法。传统的方法在信杂噪比较低的情况下难以获得目标像，本文方法利用迭代变加载对距离压缩后的连续子孔径回波进行处理，使得在抑制杂波、去除噪声的同时，目标的信息得到了保护，进而改善了低信杂噪比下的自聚焦成像质量，通过实测数据验证该方法的有效性。

Pre-filtering processing for synthetic aperture radar echo at low signal-to-clutter-noise ratio level

In the airborne synthetic aperture radar (SAR) system, the echo with low signal to clutter noise ratio (SCNR) is caused by the beam pointing deviation, partial aperture effect, and the internal system increased noise. A new method of recursive variational diagonal loading is presented to improve the performance of suppressing the clutter and noise. The conventional imaging method often requires the high correlation for radar returns, which is fail at the low SCNR level.  By the recursive variational diagonal loading at the continuous sub aperture echo after range compression, the clutter and noise are suppressed, and the information of target have been maintained and sufficiently protected. The quality of image is improved by self focusing processing at low SCNR condition. The results of the raw data have proved the validity of the proposed method.