Research On Coupling Effect Of Rough Surface And Upper Target In High Power Electromagnetic Environment

The research on the composite electromagnetic scattering of targets and rough surfaces has always been an important topic in the field of computational electromagnetics,this aspect of research has important theoretical significance in the fields of target detection,resource exploration,and microwave remote sensing under complex ground and sea backgrounds.Compared with free space,the clutter signal generated by th e coupling between the target and the rough surface will mask the target's echo signal to a large extent,which will have a certain impact on the analysis of the results,so that the research in this field has practical application value.At present,the relevant research is mainly in the frequency domain,and the study of the time domain characteristics requires corresponding Fourier transform on the basis of the frequency domain.Therefore,the calculation of the time domain characteristics in the complex rough surface model requires huge resources.The quasi-one-dimensional FDTD method is the FDTD algorithm obtained after discretizing and repairing the positive Maxwell equations.Its biggest advantage is that it can directly study its time-domain characteristics in a more complex rough surface and target composite scattering model,this method takes the way of introducing plane wave sources of arbitrary angles by connecting boundaries,which also solves the problem that it is difficult to introduce plane wave sources with oblique incidence in layered half-space media.In this Thesis,the quasi-one-dimensional FDTD method is introduced to model and theoretically calculate the composite electromagnetic scattering models of various types of rough surfaces and their targets,these include the one-dimensional single-layer rough surface and layered rough surface scattering models,the one-dimensional single-layer rough surface and the above plate,semi-buried target composite scattering model,and the layered rough surface and its upper plate,semi-buried target composite scattering model.Write relevant programs to simulate and analyze the electromagnetic scattering characteristics under different incident wave modes and different rough surface models.Compare and verify the simulation results with the COMSOL software simulation results,and the comparative analysis proves that the quasi-one-dimensional FDTD method used in this thesis has good accuracy in the research of electromagnetic scattering of rough surfaces.On this basis,the quasi-one-dimensional FDTD method is used to calculate and analyze the time-domain scattering characteristics of different rough surface models,by comparing the time-domain simulation waveforms under different rough surface types,different media parameters and different incident angles,the variation law of time-domain characteristics with each parameter is summarized.In addition,this thesis also compares the memory and time steps of the one-dimensional FDTD method and the two-dimensional FDTD method,the results show that the memory occupation of the two methods is roughly the same under the same calculation model.However,the quasi-one-dimensional FDTD method requires fewer time steps,about 1/3 of the two-dimensional FDTD method,so its calculation efficiency is higher and the calculation resources are saved more.It provides a certain theoretical basis for the research of the electromagnetic scattering problems of rough surfaces in the actual natural environment.