Research On Scattering Echo And Large Squint SAR Imaging Of Rough Sea Surface

The research of scattering echo and SAR imaging in complex marine environment is of great significance in the fields of marine remote sensing,marine resources exploration,target detection and recognition and so on.As a high-resolution microwave detection equipment,SAR has the ability to obtain target two-dimensional image information in complex environment.By analyzing the SAR image of complex marine environment,it helps people fully understand the complex scattering mechanism of the ocean.Based on this,this paper mainly studies the sea surface electromagnetic scattering in complex marine environment,various influencing factors of sea surface SAR imaging,and the simulation of large squint SAR imaging of electrically large sea surface,The electromagnetic scattering model under high sea conditions and the imaging algorithm of sea surface high squint SAR are established,and the sea surface SAR imaging is simulated.The main research contents of this paper are as follows:1.Three scattering mechanisms of the sea surface are analyzed,including the mirror reflection mechanism in the case of small incident angle,the Bragg scattering mechanism in the case of medium incident angle and other scattering mechanisms in the case of grazing incidence.Based on Fuks perturbation theory and Kirchhoff approximation theory,the refined facet scattering filed model is studied,and the correctness of the model is verified by simulation.The changes of dielectric constant and sea surface scattering coefficient with sea temperature and salinity in different wave bands are analyzed in detail,and the scattering coefficients of sea surface in different wave bands are compared.2.This paper analyzes and introduces the velocity bunching modulation mechanism of sea surface SAR imaging,and then focuses on the influence of wind speed,hydrodynamics modulation,velocity bunching modulation and other factors on single bistatic sea surface SAR imaging.Finally,a complete electromagnetic scattering model under high sea conditions is established based on nonlinear creamer model,the refined facet scattering filed model and broken wave theory,It focuses on the distribution of breaking points on the sea surface under different wind speeds and the influence of considering the breaking wave or not on the sea surface monostatic and bistatic SAR imaging under HH polarization and VV polarization.3.The large squint SAR imaging simulation of electrically large sea surface is studied.Firstly,the echo signal of squint SAR is analyzed,and then the fourth-order Taylor series expansion of radar instantaneous squint equation is deduced.Finally,based on the velocity bunching modulation mechanism of sea wave and the squint equation of radar high-order term,the imaging algorithm suitable for processing sea surface SAR under large squint is established,and the sea surface SAR imaging simulation of large scene and large squint is carried out.