Research On Motion Compensation Method Of High-resolution Unmanned Aerial Vehicle SAR Under Large Measurement Error

Synthetic aperture radar,as an active ground detection system,obtains the target by coherently processing the broadband echo signals received by the radar at different spatial positions within a certain accumulation time through the relative motion between the radar and the loading platform.The two-dimensional image of the target,so that people can actually see the real image of the target.With all-day,all-weather working characteristics.It has been widely used in both military and civilian fields.In the actual measurement of the UAV,the carrier aircraft must not be able to move along the ideal route.Affected by external factors such as unstable airflow in the atmosphere,it may deviate from the predetermined trajectory,causing the antenna phase center to shift and the flight attitude to deviate.change,resulting in a motion error.The motion error directly affects the envelope and phase of the echo signal.result in inability to image.Therefore,motion compensation technology is indispensable in UAV SAR processing.Combined with the measured data,this paper focuses on the motion compensation technology of UAV SAR under the extremly large elevation angle and a combined autofocus method based on statistical histogram proposed in special scenarios.Firstly,the basic principles of SAR imaging and some basic imaging algorithms are introduced,which lays a theoretical foundation for the design of subsequent motion compensation algorithms.The correctness of the imaging algorithm is verified by simulation experiments.Then,the motion error of the UAV SAR under the large-down view angle is analyzed,and it is concluded that the phase error of the high-order space variation must be solved in the large-down view angle imaging processing.A motion compensation algorithm based on an improved phase-weighted PGA.It includes non-space-variant phase error estimation,space-variant phase error estimation,and full-aperture cardiac phase stitching.And compared with the motion compensation algorithm based on traditional PGA,the effectiveness of the algorithm proposed in this paper is verified by the simulation test.Finally,when there are not enough strong scattering points in the scene,the PGA algorithm may have a phase estimation error and the focusing will fail.But in this scenario,MDA can focus effectively.At this time,the strength of the point target in the image can be counted,the proportion of the stronger point target in the image can be obtained through the statistical histogram,and the threshold value can be set.On the basis of this threshold value,a combination of The self-focusing compensation method improves the stability of the motion compensation algorithm and retains the focusing accuracy of the original algorithm to a certain extent.Finally,the algorithm is verified by the measured data and good results are obtained.