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.