SAR Imaging From Missing Raw Data Recovery Based On Compressed Sensing

Synthetic Aperture Radar(SAR)is an active microwave remote sensing imaging system with all-weather,high-resolution,strong penetration and multi-parameter detection characteristics.The characteristics of SAR make it have broad application prospects in the fields of vegetation protection,terrain mapping,resource detection,disaster assessment and military reconnaissance.The deepening and expansion of the application field of SAR technology requires that the SAR system can have high-resolution imaging capabilities in different systems and working modes,and can obtain satisfactory high-quality images under various practical conditions.The problem of missing data exists in signal processing fields such as astronomical observation,remote sensing radar,and sonar detection,especially in the field of radar imaging.In the actual work of SAR system,SAR echo data will be missing due to various reasons.At this time,if the missing echo data is directly imaged by the traditional SAR imaging processing method,the imaging results may be blurred,defocused,aliased,or even false targets,resulting in the degradation of the SAR image quality.High-quality SAR images are the key to presenting the accuracy and reliability of target information,and can provide a basis for ensuring the smooth development of various research work on SAR technology.Therefore,high-resolution SAR imaging technology is the basis and key of SAR research.In this paper,an in-depth study on the problem of missing SAR echo data is carried out.The main research contents and innovations can be summarized as follows:1.The types of missing SAR data in azimuth are studied and analyzed.SAR echo data may be missing in azimuth for various reasons.In this paper,the data missing of SAR in the azimuth direction is divided into periodic missing and random missing.The reasons of periodic missing and random missing are analyzed respectively,and the missing model of SAR echo data is given.2.The recovery imaging problem of SAR echo data with periodic missing in azimuth direction is studied.Due to mission requirements,signal undersampling and other reasons,the echo data collected by the SAR system may be periodically missing in the azimuth direction.At this time,if the traditional imaging method is still used for direct imaging,the imaging quality will be degraded.Aiming at this problem,this paper proposes a recovery imaging method for azimuth periodic missing SAR data based on the SWOMP algorithm.The proposed method can effectively suppress false targets in azimuth and improve the imaging quality of periodically missing SAR echo data.The effectiveness and feasibility of the proposed method are verified by simulation experiments.3.The problem of SAR echo data recovery imaging under the condition of random missing azimuth is studied.In the process of transmitting and receiving electromagnetic waves by the SAR system,the received SAR echo data may be randomly missing in the azimuth due to object occlusion,interference,system failure and other reasons.If the missing SAR echo data is processed by traditional imaging algorithms,defocusing and false targets may appear.Aiming at this problem,this paper proposes a recovery imaging method for azimuth random missing SAR data based on the SASt OMP algorithm.This method can recover images from random missing SAR data with unknown sparsity.The method proposed can suppress the azimuthal defocus phenomenon and improve the focusing effect of point targets,thereby improving the SAR imaging quality in the case of random missing data.Moreover,this method can adapt to a wider selection range of threshold parameters.Simulation results demonstrate the feasibility and effectiveness of the proposed method.