Research On SAR Image Sidelobe Suppression Technology

Synthetic aperture radar(SAR)has been widely leveraged in military and civil fields,especially in reconnaissance,surveillance and target positioning.With the development of technology in the field of military,many new SAR applications,such as unmanned and unmanned aerial vehicle flight platform,can undertake long-term strategic reconnaissance,distinguish between the area of all kinds of camouflage,detect the movement of the enemy submarines,penetrate and find the mobile missile platform hidden in the forest.If combining with the C4 ISR system,the commander will be able to deploy a second artillery bunker in the desert and display moving targets to clear the fog of battle and get a handle on the situation.Currently,SAR mounted on unmanned aerial vehicles is steadily increasing in the demand for surveillance and reconnaissance missions,which can collect tactical and strategic information.Specifically,SAR mounted on unmanned aerial vehicles has replaced some optical and infrared sensors because it provides a number of unique and valuable functions,such as long-range,all-weather and all-weather imaging,ground-moving target indication and focused imaging.Unmanned aerial vehicle SAR system,which can be repeatedly observed as required,has become an indispensable telemetry tool for military and people's lives in many countries due to its low cost,small size,low risk and other characteristics.Therefore,the research of SAR is of great significance to the progress of military,technology and national security.In this paper,the SAR image side lobe processing technology is studied for handling the side lobe phenomenon in SAR image.This paper studies the theoretical basis of correlation in the whole SAR imaging process,and analyzes and summarizes the correlation algorithms in the field of SAR image side lobe suppression.The traditional SVA algorithm and some improved SVA algorithms mainly optimize in two fields: on the one hand,filter related parameters,such as filter order or other filter parameters;on the other hand,the selection of optimal weight coefficient of impulse response for the weighted window function.Although traditional SVA algorithms suppress the side lobe to some extent and improve the image resolution,but are still some obvious side lobe.In this paper,a new side lobe suppression algorithm is proposed from another dimension.The azimuth upward doppler frequency shift algorithm is considered,and the algorithm is based on the complex image data for theoretical derivation.The derived theory algorithm is applied to two groups with three point target simulation of SAR image and actual SAR image.In the two groups of simulation image,one group is ideally excluding doppler frequency shift of SAR images,another group contains a certain amount of doppler frequency shift of SAR image.The actual SAR images usually contains doppler frequency shift.When other conditions are consistent,the application results of the traditional and new SVA algorithms in two different sets of simulated SAR images are analyzed and compared.It is verified that the doppler frequency shift has a certain impact on SAR image side lobe suppression,and the effectiveness of the new algorithm in the field of SAR image side lobe suppression is also verified.Finally,our proposed algorithm is applied to the actual SAR image,and the final image result shows that the proposed algorithm can suppress side lobe more effectively than the traditional SVA algorithm.