Research On Sidelobe Suppression Algorithm For Squint SAR Imaging

Synthetic Aperture Radar(SAR),as a high-resolution imaging radar,can obtain high-quality images and plays an important role in the contemporary remote sensing field.With the improvement of modern people’s quality of life,synthetic aperture radar has been widely used in all aspects and has become a hot topic for modern scholars.So far,many effective SAR imaging and image processing methods have been proposed in the field of radar imaging technology.In the SAR imaging process,because of the limited range of the two-dimensional frequency domain support in the range and azimuth direction,side lobes appear in the target SAR image.If the SAR imaging scene contains many strong target points,its sidelobes will cause the weak target points to be distorted,which will affect the SAR imaging results and reduce the SAR image quality.Therefore,sidelobe suppression is particularly important in SAR image processing.Aiming at the target in the squint situation,this paper studies the sidelobe suppression technology of SAR image.This paper proposes to correct the side lobes in the squint situation to "cross",and then combine the MSVA algorithm to realize the side lobes suppression in the SAR image in the squint situation.Calculate the image contrast(IC)and entropy(IE)of SAR images before and after sidelobe suppression to prove the effectiveness of the algorithm.The main research contents of this paper are as follows:1.Research the spatial apodization algorithm(SVA)and some improved SVA algorithms,and apply them to the SAR imaging in the frontal mode to verify the sidelobe suppression effect.Analyze and derive the formula,respectively use the traditional SVA algorithm and the improved SVA algorithm to calculate pixel by pixel in the SAR image,and obtain different results after sidelobe suppression.Compare the IC and IE values ??before and after the suppression on the SAR images after different sidelobe suppression algorithms to judge the advantages and disadvantages of each algorithm.2.The sidelobe suppression process of squint SAR imaging is studied,and the sidelobe tilt correction,sidelobe suppression and geometric distortion correction process are analyzed in detail.In the case of squint,due to the choice of the coordinate system and the existence of distance movement,the side lobes no longer appear as "crosses",and there is a tilt phenomenon.The SVA algorithm and its improved algorithm can only achieve sidelobe suppression when the sidelobes are "cross",so sidelobe tilt correction is required for squint SAR imaging images.Considering the two-dimensional Fourier distortion characteristics,the sidelobe tilt correction is achieved by means of phase factor compensation.After the corrected side lobes are "cross",SVA and the improved SVA algorithm can be used to achieve side lobe suppression in squint SAR images.Since the geometrical position of the target will be distorted in the process,it is necessary to restore the spatial position,and still use the phase compensation method to finally realize the sidelobe suppression of the squint SAR image and restore the target spatial position.