A Research Of Imaging Mode And Algorithm Of Thz Curvilinear SAR

As a frontier research field of SAR imaging technology,terahertz SAR has a very broad application prospect.The synthetic aperture time of terahertz SAR is short,and the flight trajectory of radar carrier changes little in the synthetic aperture time.The influence on imaging can be ignored under certain conditions.However,the study of terahertz SAR still stays in the straight track or circular track mode,the curve mode of terahertz SAR is not mature in both mode and algorithm.Based on this,the imaging mode and algorithm of THz curve SAR are studied in this paper,and the imaging mode expansion,subaperture division and imaging preprocessing methods are analyzed in depth.The main research contents of this paper are as follows :1.The basic principle of uniform linear SAR and uniform circular SAR imaging is introduced.The imaging resolution of SAR is deduced by analyzing the echo signal of SAR.For the imaging algorithm,the distance preprocessing steps including dechirp processing and dechirp processing are deduced,and then the PFA imaging algorithm is introduced.2.Aiming at the imaging mode of terahertz curve SAR,according to the characteristics of short synthetic aperture time and high bandwidth in terahertz band,around the concept of curve continuous bunching mode,the constraint conditions of approximating curve trajectory to ideal straight line trajectory or circular trajectory are studied,and the acceleration constraint range and carrier radius deviation range that restrict imaging are derived.3.Aiming at the imaging algorithm of terahertz curve SAR,the PFA algorithm based on curve SAR is introduced.According to the constraint conditions of wavenumber aliasing and the principle of resolution matching,a low constraint subaperture division method is proposed.4.Aiming at the wavenumber domain distribution of curve SAR,the data utilization rate of radar echo interpolation in wavenumber domain is analyzed,and the general method to improve the utilization rate is studied.Based on this,the interpolation area preprocessing method is proposed,including determining the center coordinates of the interpolation area by the geometric center point in the wavenumber domain and determining the center coordinates of the interpolation area by the wavenumber domain mapping.Aiming at the defects of polar coordinate interpolation method in fixed scene,a wavenumber domain rotation algorithm is proposed,which greatly improves the utilization rate of data.In general,this paper studies the imaging algorithm of terahertz curve SAR,and analyzes the constraint conditions that the curve trajectory is approximately linear or circular trajectory.Through the study of terahertz curve SAR imaging algorithm,the imaging quality of existing imaging algorithms is improved.