Study On Modeling Of Electromagnetic Scattering From Targets In A Rough Half Space

The modeling of target electromagnetic scattering characteristics is of great value in the fields of radar target recognition and detection,stealth and anti-stealth operations,and mineral exploration.In the real world,except for air and sky flying targets,a large number of targets are in a non-uniform environment,such as a typical semi-space environment such as ground and sea.At this time,the electromagnetic scattering of the target not only depends on itself,but the environment will greatly affect its scattering characteristics.Therefore,the composite scattering of the target and the environment requires the establishment of an integrated analysis model.This paper conducts research on the typical environment of the sea surface,proposes a new type of rough half-space environment model,and models and analyzes the electromagnetic scattering characteristics of targets in this environment based on the integral equation method.The main contents include:Aiming at the target modeling,this article uses the operator theory to review the basic principles of the method of moments,and elaborates its implementation process,especially the most commonly used RWG basis function form.On this basis,the above operators are embodied and the surface integral equation of electromagnetic field is introduced.In order to calculate the large target,this article further introduces the mathematical principles and implementation steps of the multi-layer fast multipole method.This method uses group aggregation and overall transfer to reduce the number of exchange chains in the far range,which can greatly reduce the integral of the method of moments.The computational complexity of the equation speeds up the solution process.In this paper,a program is implemented to model and analyze typical target electromagnetic scattering,and compare the results with simulation software to verify the accuracy and practicability of the above method in target characteristic modeling.In order to consider the composite scattering of the target and the sea surface,it is necessary to establish a rough surface model of the sea surface.This article introduces the concept of the sea spectrum and explains the detailed process of generating a rough sea surface model from the sea spectrum.Different from the actual sea surface,the sea surface model required for calculation has a certain size,that is,there is a boundary.In order to suppress the "boundary effect" that appears at the boundary of the sea surface model,this paper uses a two-dimensional cone incident wave to gradually cut off the energy on the illuminated surface.On this basis,the process of generating the composite model of the rough sea surface and the target is further introduced.The target and the truncated sea surface are taken as a composite target,and the integrated modeling calculation is carried out on the target and the truncated sea surface through the above method.In the case of grazing incidence,the irradiated area incidence will increase sharply,making the required sea surface size increase sharply,which brings about a huge unknown quantity of solution.This paper introduces a new type of rough half-space model.First use the plane half space as a basic model,and use the half space dyadic Green function to describe the scattering contribution of the infinite background.On this basis,the generated finite rough surface is superimposed on the plane half space.The model is combined with the actual target to solve the scattering of rough half-space target.Since the coupling between the sea surface and the target decreases with the increase of the distance,the plane interface can be used to replace the rough surface for the coupling calculation with the target at a distance from the target,avoiding the problem of space truncation.Specifically,this article first derives the dyadic Green's function and incident field in a plane half space in detail,and gives the discrete matrix expressions of the electric field integral equation and the magnetic field integral equation in the half space.In order to smoothly transition the rough surface boundary to the plane half-space interface,this paper introduces an attenuation window function to smoothly cut the rough surface boundary.Finally,the rough surface is attached to the plane half-space,which is regarded as a special open-body target,and a composite model is formed with the real target.The half-space method of moments is used to solve the integrated scattering.By comparing with simulation software,the correctness of the method is verified.In order to improve the ability of the scattering model to solve electrically large problems,this paper further explores the multi-layer fast multipole method based on halfspace dyadic Green's function.The aggregation transfer and configuration calculation are completed by layering the actual area and the mirror area.Solve the electromagnetic scattering of electrically large targets in a rough half-space environment.Finally,through the research of ship model scattering in rough half-space,the ability of the proposed method to deal with electrically large problems is verified.