Processing Of Squinted SAR Data

Synthetic Aperture Radar(SAR)is a kind of high-resolution imaging radar,which can continuously detect targets all the day,and it is not affected by external factors such as weather.It is an important electronic equipment in current detection technology.On the other hand,SAR can penetrate through surface shielding and probe deep into the interior of a target,so it can monitor agricultural crops and natural disasters in real time.SAR,often mounted on mobile platforms such as aircraft and satellites,can collect data on a wide range of scenes.For long-range targets,it can also ensure the high resolution of imaging.The acquired images can help solve many problems in military reconnaissance and civil fields,and it are widely used in many fields such as military detection,mapping,guidance,environmental remote sensing and resource exploration.With the change of data acquisition methods and the improvement of imaging requirements,SAR imaging algorithm has become a research hotspot in the field of image processing.At present,due to the constraint of observation and investigation ability of high requirements,we need to detect targets in the ground scene in advance,it has high squint angle,so most of radar data are squint SAR data,classical imaging algorithms have does not apply to the current working situation,the development of new algorithms with focus on imaging and improve image quality need to be resolved.The imaging of squinted SAR data and subsequent image processing remains a huge challenge.In this paper,the squinted SAR data imaging and image quality improvement are studied in detail.The main research results are as follows:Firstly,based on the original polar coordinate format algorithm(PFA),an improved PFA algorithm(MPFA)based on the rotating coordinate system is proposed.This method is used to process the SAR data with squinted information.The main idea is to reconstruct the original coordinate system by rotating the same angle of squinted SAR data,and calculate the instantaneous distance in the new coordinate system.The influence caused by squinted case is eliminated by rotation operation,and the imaging operation is carried out in the positive side looking case condition,breaking the limitation of PFA processing of squinted SAR data.After focusing imaging,the target does not appear skewed cross,which has good effect and effectively simplifies the processing process of subsequent image quality improvement.Secondly,in order to improve the image quality,we mainly discuss the problem of image side lobes control.Based on the classical algorithm of spatially variant variation(SVA),we put forward the filtering method of variable scale polynomial(NPF).The main idea of this method is to determine the weighting coefficient adaptively according to the data characteristics,which has the flexibility.However,this method will inevitably lose the image information while controlling the side lobes.Even if the background fusion method can supplement part of the lost image information and balance the overall energy of the image,the image quality will still be affected.Again in order to solve this problem,this method puts forward a new solution,using the compressed sensing(CS)theory,introducing orthogonal matching pursuit(OMP)algorithm,SAR images are reconstructed by OMP algorithm with NPF images as prior information,finally,background fusion is carried out,while control side lobes,able to retain image information to the greatest extent,restore the SAR images.In addition,the algorithm is further optimized to improve the efficiency of the algorithm,so as to improve the quality of large-scale SAR images in a short time.