Research On FMCW SAR Imaging Method Of Missile Borne Platform

In order to deal with the current complex battlefield environment,precision guided weapons have always been an important means of accurately hitting targets in the battlefield.Not only rapid penetration and precise identification of attacks are needed,but all-weather,all-weather and long-range combat capability is also required.Synthetic aperture radar(SAR)is one of the methods for precision guidance of missiles and has received a lot of research.Compared with spaceborne and airborne SAR imaging,its characteristics of high speed,large strabismus,and curved motion make it the main difference between on-board imaging and spaceborne and airborne imaging,and it is also a key issue to be resolved in missile-borne imaging.Frequency Modulated Continuous Wave(FMCW)SAR has the advantages of small size,light weight and low peak power.Therefore,FMCW SAR has great application potential in the field of precision guidance.This paper first studies the imaging process of FMCW SAR,which is different from the traditional pulsed SAR imaging.In the FMCW SAR imaging,the problems caused by the continuous motion of the in-pulse carrier platform cannot be neglected,and a detailed analysis is performed to indicate the continuity within the pulse.The effect of exercise on imaging increases with the increase of the oblique viewing angle,and it is more necessary to pay attention to the influence brought by the oblique viewing condition,which needs to be considered in the imaging process.The specific analysis and imaging process of the Frequency Scaling Algorithm(FSA)under the FMCW system is given.By analyzing the motion characteristics of the missile-loaded platform,the high-speed,strabismus,and curved motion of the missile-loaded platform brings great difficulties to imaging.By analyzing the limitations of the FSA algorithm,the approximation of the second-distance-compression term is compensated in the high-squint condition.The next becomes unsuitable,limiting the application of the FSA algorithm.By analyzing the effects of the secondary distance compression term,that is,the higher order terms,the higher order terms cannot be ignored with the increase of the imaging oblique viewing angle,and a nonlinear frequency scaling algorithm(NFSA)is given to solve the secondary distance compression.The item's vacancy problem and compensation for higher items.However,the complexity of the ballistic motion,such as avoidance flight or subduction flight,is a non-uniform non-linear motion,which makes the traditional imaging method difficult to apply in the ballistic platform,and all need to be improved.According to the characteristics of guided missiles,through the decomposition of the missile's flight trajectory,distance-distance motion compensation and azimuth non-uniform Fourier transform are used to solve the problem of non-uniform non-linear motion platform imaging.Finally,combined with the improved NFSA imaging algorithm,it enables imaging on an airborne platform.Through imaging analysis,good imaging results are obtained.