Research On Fast Imaging And Real-time Processing Of Arbitrary Trajectory SAR

Synthetic Aperture Radar(SAR),as an active microwave active sensor,can obtain accurate information of far observation scene under all weather conditions day and night,and has been widely used in civil,military and many other fields.With the continuous development of SAR imaging technology,the working mode of the system has long been not limited to the linear orbit,and various imaging modes emerge one after another.Arbitrary trajectory SAR can flexibly adjust the radar trajectory according to the observation requirements and the surrounding environment.Therefore,it can obtain multi-angle target scattering information,and has stronger detection,recognition and continuous monitoring ability in complex environment.It has become one of the most promising imaging models.However,compared with the traditional imaging mode,the arbitrary trajectory SAR has the characteristics like flexible trajectory,which make the conventional SAR imaging configuration and imaging method no longer applicable.In response to the above problems,this paper conducts research on fast imaging algorithms and real-time processing of arbitrary trajectory SAR,which is specifically divided into the following three points:1.Aiming at the problem that the resolution formula of traditional SAR system is no longer applicable under arbitrary trajectory working mode,a resolution evaluation method based on wavenumber spectrum is proposed.This method reveals the relationship between radar trajectory and system resolution.It can be used for resolution evaluation of linear,circular,and arbitrary trajectory SAR systems and radar trajectory planning,and lays a theoretical foundation for subsequent research on arbitrary trajectory SAR imaging algorithms.2.Aiming at the problem that the frequency domain algorithm is difficult to apply to arbitrary trajectory SAR imaging mode,and the accuracy and efficiency of traditional time domain fast imaging algorithms are mutually restricted,an improved FFBP imaging method based on segmented projection and global fusion is proposed.By introducing sub-aperture reference point,this method breaks through the limitation of traditional FFBP algorithm based on local polar grid,and can perform projection and fusion on the global rectangular coordinate grid.The improved algorithm has the advantages of simple sub-image fusion process,no polar to rectangular coordinate transformation,and convenient projection range limitation.It effectively solves the contradiction between imaging accuracy and algorithm efficiency,and realizes high-efficiency and high-precision imaging of arbitrary trajectory SAR.3.Aiming at the real-time and high-resolution imaging requirements of arbitrary trajectory SAR,this paper completes the design of real-time processing software for improved algorithms based on TMS320C6678 isomorphic multi-core DSP.Firstly,the imaging module design is completed by combining DSP hardware resources and algorithm processing flow,and functions such as adaptive quantization are added according to the actual needs of the project.Subsequently,the real-time processing software was optimized in terms of loop optimization and the use of inline functions,and the compatibility of the imaging software was maintained by adding extreme situation protection and other means.Finally,simulation and measured data processing are carried out to prove the correctness and efficiency of the improved FFBP algorithm real-time processing software design.