PO-SBR Algorithm For Analysis Of Composite Scattering And HRRP From The Target And Rough Surface

The modern warfare in the context of complex environment has promoted the rapid development of scientific and innovative technologies.The technical requirements of target stealth and recognition,environmental remote sensing,and ocean exploration have placed higher demands on the scattering of target and environmental composite models,such as simple calculation method,less computation time,and less storage consumption.This thesis focus on the open electromagnetic field of rough surface and target,the method that the physical optics(PO)and shooting and bouncing rays(SBR)are utilized.The physical optics is a high-frequency approximation method that calculates the induced electromagnetic current on the surface of the scatter based on the geometric optical approximation,and the scattered field are approximated as the integral of the induced electromagnetic current.The SBR is a hybrid method of the geometric optical(GO)method and the physical optical method(PO).The geometrical optics method is used to find the reflection surface element of the target,and the physical field method is used to solve the scattering field as well.Therefore,the SBR method is more accurate than the PO method for solving the complex targets that including dihedral and trihedral angles.In this thesis,two methods are used to solve the electromagnetic scattering field of the rough surface and the target,and the high-resolution distance image of the target is obtained based on the target scattering field.The main work of the thesis including: 1.The combination of PO and PO is applied to solve the composite scattering of the target and the rough surface numerically.The rough surface and the target scattering are solved by PO calculation,and the coupling between target and rough surface are considered according to the Huygens equivalent principle and the idea of multipath scattering as well.This method is used to solve the composite scattering of both one-dimensional rough surface and single two-dimensional target,and by comparing to the traditional MoMent method(MoM),the results show that those two methods matched well.Based on this,the composite model is extended to multiple targets above the rough rub surface.The results of scattering are compared with the boundary finite element(FE-BI)method.The validation of the algorithm for the rough surface and multi-objective composite model is carried out as well.In addition,the effects of incident wave parameters,rough surface parameters and target parameters on the scattering of composite models are studied at the same time.2.The physical optics method are able to solve the electromagnetic scattering of some simple targets,but for the more complex target models that including the dihedral and trihedral angles,the coupling effect cannot be taken into consideration,which would lead to the big difference when comparing between the numerical results and the measured results of the PO method.Therefore,in this thesis,the SBR method is proposed to calculate the electromagnetic scattering of complex targets.For the edge scattering problem of the target,the physical diffraction theory(PTD)is used to calculate the edge diffraction field of the model.and the verification of algorithm are implemented by comparing the results obtained from the simulation results and the multi-pole(MLFMM)method in commercial software.3.Based on the PO and SBR methods,a hybrid method of PO-SBR is proposed and applied to the scattering field calculation of the composite model of the two-dimensional rough surface and the upper three-dimensional object.The PO method is used to calculate the primary scattering of the rough surface,the SBR method is used to calculate the self-scattering of the target,and the coupling scattering between the rough surface and the target is calculated according to the Huygens equivalent principle and the idea of multipath scattering as well.The PO-SBR method is used to calculate the difference field radar scattering coefficient of the target(one or more)above the rough surface.The correctness of the method is verified by the comparison with the fast multipole method of commercial software.As for the problem of high time consumption in the iterative calculation of the algorithm,based on the OpenMP parallel acceleration theory,the programming code is parallelized,which reduces the running time effectively.4.The basic principle of high resolution range image is introduced in this thesis.The imaging mechanism of one-dimensional range image is analyzed as well.Besides,based on the backward broadband scattering data of the rough surface and the target composite model mentioned above,the High Resolve the distance image(HRRP)of the composite model is obtained by using the inverse fast Fourier transformation.The number,position as well as amplitude characteristics of the peaks in the total HRRP are analyzed,and the specific sources of the peaks are studied from the physical mechanism as well.