| The study of electromagnetic characteristics of targets in the land-sea junction area has very important military and civilian value.In this thesis,related researches are carried out on the target compound scattering in the land-sea junction area.This thesis firstly realizes the highprecision geometric modeling of the land-sea junction area,and at the same time improves the SBR algorithm,which provides a technical basis for the engineering realization of computational simulation.Next,based on the far-field electromagnetic scattering obtained by the calculation simulation,the electromagnetic scattering characteristics,high resolution range profile and Doppler spectrum of the target in the land-sea junction area are calculated and analyzed,and the calculation results are compared with the calculation results under the pure sea area.In contrast,statistical analysis of the similarities and differences of target electromagnetic characteristics in different environments provides relevant theoretical and data basis for target detection and radar clutter suppression technology.The main work is as follows:1.Firstly,the offshore spectrum is modeled based on the Jonswap sea spectrum with the addition of the shallowing factor,and the offshore sea surface and the land rough surface are obtained by the linear filtering method.By introducing the weighted arctangent function to the boundary of the two rough surfaces,the smooth connection between the offshore sea surface and the land rough surface is achieved,and the refined geometric modeling of the land-sea interface region is completed.The model of land-sea junction area is characterized by large size and high accuracy of sectioning.On the premise of ensuring the accuracy of simulation results,in order to further improve the computational efficiency of SBR algorithm,this thesis introduces Open GL,Open Mesh and other frameworks to improve the process of precluding shaded face elements and querying adjacent face elements.Meanwhile,the raytracing process is optimized and accelerated based on the data structure of KD-Tree,which provides a technical basis for the engineering implementation of high-performance electromagnetic scattering calculation in the land-sea junction area;2.With the improved SBR algorithm,the far-field scattering of targets such as landing craft and destroyers are calculated,and the scattering characteristics of different targets with different structures were analyzed and summarized.The composite far-field scattering of the target in different scenes is calculated,the coupling mechanism of targets and background environment is statistically summarized,and the difference of electromagnetic scattering in different environments are compared.Then the HRRP of the target is calculated based on the target's backward broadband scattering echo signal,and the imaging mechanism of the target HRRP is analyzed based on ray theory,and the differences of HRRP in different environments are compared;3.Research on the Doppler spectrum of the land-sea junction area.A quasi-static method is used to simulate the time-varying sea surface,and the Doppler spectrum is obtained through the calculated radar echo time series.This thesis mainly analyzes the effects of radar parameters and rough surface parameters on Doppler spectrum,explains the mechanism of Doppler frequency shift and broadening phenomenon,and compares the differences in Doppler spectrum between the land-sea junction area and the sea surface area.The analysis summarizes the main factors affecting the Doppler spectrum. |
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