Time-Domain Fast Imaging Algorithm For Array Forward-Looking Synthetic Aperture Radar Research

Different from single-antenna synthetic aperture radar(SAR),Array Forwardlooking Synthetic Aperture Radar(AFSAR)is a SAR system working with multiantenna elements,and the geometry of AFSAR is more diverse,which can meet the forward-looking SAR application in a variety of scenarios.Because the time domain algorithm does not have the constraint of constant bearing assumption,it can effectively avoid the problem of coupling azimuth and distance in forward imaging.This paper is based on AFSAR and combined with time-domain fast algorithms.The details are as follows:1.In the track direction,due to the movement of the aircraft,a virtual synthetic aperture will be formed.The forward-looking SAR imaging area is located in front of the airborne platform.The contribution of the virtual synthetic aperture to the azimuth resolution provided by the area directly in front of the aircraft movement is zero,even if it is close to the track.Due to the small oblique viewing angle,the cross-course resolution provided by virtual synthetic aperture is still very low.Therefore,the low cross-course resolution is the main problem of forward-looking SAR imaging.In order to solve this problem,AFSAR forms a real synthetic aperture of forward-looking crosscourse by arranging antenna arrays in the cross-course direction.The real synthetic aperture can effectively improve the azimuth resolution of forward-looking SAR imaging.In the case of small scenes,the contribution of the virtual synthetic aperture to the cross-direction resolution of AFSAR imaging is limited,and the cross-direction resolution of AFSAR is mainly provided by the array antenna.Cartesian Fast Back Projection(CFBP)algorithm,and finally coherently stack the CFBP images at each slow time sampling point,and finally obtain high-quality AFSAR images with high processing efficiency.Experimental simulation verifies the effectiveness of the method.2.To increase the cross-course resolution of AFSAR,the method of increasing the length of the antenna array can be adopted.However,this method will increase the number of array elements,thereby increasing the complexity of the SAR platform system and the cost of making the system,and in many practical applications.The length of the antenna array is limited.To solve this problem,this paper adopts the antenna array of Multiple Input Multiple Out(MIMO)mode.By optimizing the array configuration,the MIMO mode can form a column of virtual antenna arrays through the equivalent phase center with a small number of transceiver elements to realize SAR.Forward-looking imaging improves the cross-row resolution ability;according to the configuration characteristics and signal characteristics of MIMO forward-looking imaging,the time-domain fast imaging method is studied to obtain high-quality AFSAR images and take into account high processing efficiency.Experimental simulation verifies the effectiveness of the method.