Research On Imaging Technology Of High-band And High-frame-rate SAR

Compared with the conventional airborne Synthetic Aperture Radar(SAR)which requires a long accumulation time,low imaging frame rate characteristics for achieving high-resolution,high-band and high-frame-rate SAR can effectively detect the target and track a specific target through frames of clear images.This paper focuses on imaging of high-band and high-frame-rate SAR.Through theoretical simulation and measured data processing,we mainly study motion error and imaging algorithm.The main researches are as follows:In this paper,the high-band and high-frame-rate SAR imaging model is introduced and the dechirping model is deduced theoretically and measured data is processed.In addition,we demonstrate its specific frame rate indicators.In a certain overlap rate,you can guarantee the SAR video frame resolution to maintain a high frame rate.For high-band SAR,small high-frequency vibrations of the platform can also lead to defocusing of the image.In this paper,the influence of high frequency components of vibration error is deduced theoretically and simulated at the signal level,which proves the validity of theoretical derivation and the necessity of compensating the high frequency components of vibration error.Then,two kinds of motion compensation algorithms(TD-PGA and time-domain PACE)are analyzed and compared to compensate the high frequency components of vibration error.Two compensation schemes are proposed: one is suppress the small high-frequency vibration eroor of the platform effectively by optical vibration isolation platform and combine the time domain phase gradient autofocus algorithm based on the motion sensor measurement and echo data to realize the precise focusing of the SAR image.The other is to use the PACE algorithm without any preset time to compensate the motion error directly,and to increase the computing speed by under-sampling and interpolation.Based on circular SAR the important working mode of high frame rate,the time-domain back-projection algorithm and the wave-front reconstruction algorithm are reduced in detail,and the processing steps and flow chart are given.Taking the point target as an example,the signal simulation is carried out to verify the effectiveness of the algorithm.The two-dimensional spatial wavenumber domain of the full-aperture SAR is circular.Through the molecular aperture imaging,the resolution of distance and azimuth is continuously coupled with the distance and azimuth.When they are fully coupled,it achieves the ultimate resolution,and also brings a three-dimensional imaging capability.Finally,the validity of the time-domain algorithm is proved by the processing of GOTCHA's SAR data,and the efficient generation of SAR video is proposed based one the sub-aperture imaging of the measured data.Since the scattering characteristics of the target are related to the observation angle,some targets show sub-apertures clearly.In SAR video,the scattering characteristics of the target at a particular angle of view will be more pronounced and the detection and tracking of moving targets will be more effective.