Research On Imaging Algorithm Of High Squint Missile-borne SAR

With the background of informationized warfare,weapons with long-range precision strike capability have become the focus of current research in various countries.The allweather,high-precision two-dimensional imaging capability of Synthetic Aperture Radar(SAR)makes it the trend of missile seekers.Therefore,studying SAR imaging algorithms which are suitable for high-squint working conditions of missile-borne platforms has important military significance.First,the large squint missile SAR model is analyzed,and the instantaneous slant range in the squint model is deduced.The meaning and relationship of different order items in the Taylor expansion of the instantaneous slant range is performed.Then the range walk error of the distance migration is separated to lay the foundation for the optimization of the migration correction.Then the echo signal of the ground virtual point target is deduced,and the echo data matrix is obtained through simulation,which provides the data source for the subsequent imaging algorithm verification.Secondly,this thesis analyzes the conventional SAR imaging algorithm,and points out that the conventional algorithm has poor imaging effect and large computational complexity in the high squint imaging of the missile platform.In this thesis,the correction process of the migration error is divided in the following two steps.First,the range walk is corrected in the distance frequency-azimuth time domain,thereby greatly reducing the residual migration and the two-dimensional coupling.Then,range curve and the highorder offset are corrected in the two-dimensional frequency domain,thereby completing the calibration process more accurately and efficiently.Based on the above ideas,this thesis deduces the improved Range Doppler(RD)algorithm and the improved Chirp Scaling(CS)algorithm for high squint imaging,and verifies that the improved algorithm can enhance the imaging effect for the echo data of high squint angle through the simulation and comparison experiments.Finally,this thesis studies the imaging algorithm under the missile platform based on the practical application background.As for the real-time problem of imaging on the missile platform,in order to efficiently complete azimuth pulse compression,this thesis utilizes the sub-aperture processing method to segment the radar echo azimuth signal data,and realizes the parallel processing of multiple sub-aperture data through the time-domain sub-aperture correlation algorithm.On the other hand,aiming at the motion error of the missile-borne platform,this thesis analyzes and compares the first-order and second-order error estimation methods of Doppler parameters.The sub-aperture processing to efficiently and accurately estimate the motion parameters are also combined in order to better compensate the motion error.Finally,it is verified that the improved algorithm has not only less computational complexity than the full aperture processing method,but can also obtain images with better focusing effect through performance analysis and simulation comparison.