The Analytical Solution Of Electromagnetic Scattering By A Buried Anisotropic Medium Cylinder

The research on electromagnetic scattering of buried targets is of great significance in the fields of tunnel,pipeline and mine detection,geophysical exploration and so on.In recent years,more and more scholars have analyzed and studied the electromagnetic scattering characteristics of buried dielectric cylinder in detail,and various methods for calculating the electromagnetic scattering of dielectric cylinder have appeared one after another,and the corresponding analytical process and numerical calculation results are given.Based on the image method,the addition theorem of the Bessel function and electromagnetic scattering of anisotropic dielectric cylinder,an analytical method is proposed to solve the multiple scattering problem of buried anisotropic dielectric cylinder in this thesis.Firstly,based on the theoretical knowledge of the vertical incidence of uniform plane wave on the medium dividing plane and the propagation characteristics of uniform plane wave in unbounded space,the reflected wave and transmitted wave of the uniform plane wave at the medium interface are obtained,and then the transmitted wave at the medium interface will be incident as the incident wave of the buried anisotropic dielectric cylinder,and the transmitted wave of the medium plane will be expanded by Bessel function.Then the eigenvalues and eigenvectors of the differential equation of electromagnetic field in anisotropic medium cylinder are solved by Fourier transform,and then the infinite integral obtained is transformed into the double integral of the sum of eigenvalues by using eigenvalue,and the expression of electromagnetic field in anisotropic medium cylinder is solved by introducing column vector wave function.Finally,the reflected coefficient and transmitted coefficient of anisotropic dielectric cylinder are obtained recursively by using the boundary condition that the tangential components of electric field and magnetic field on the surface of dielectric cylinder are continuous,and then the expressions of reflected wave and transmitted wave of dielectric cylinder are obtained.Then,the reflected wave of the dielectric cylinder is incident on the medium interface as the incident wave again,and the reflected wave and the transmitted wave are generated at the medium interface again.The reflected wave of the medium plane can be equivalent to the scattered wave of the image cylinder of the buried cylinder on the medium plane,that is,the image method used.The image method is used to solve the reflected wave generated by the medium boundary surface,and the reflected wave in image coordinate system is transformed by the addition theorem of Bessel function.Finally,the scattered wave of the image cylinder will be incident as the secondary incident wave of the anisotropic dielectric cylinder,and the reflected wave generated by the dielectric cylinder will be incident as the incident wave of the boundary plane,and it will be repeated until it converges.In this thesis,an analytical method based on multiple reflections is proposed to solve the electromagnetic scattering problem of a dielectric cylinder buried in a homogeneous dielectric halfspace.Based on the numerical calculation results of the theory obtained in this thesis,the influence of many factors such as the dielectric characteristics,size and buried depth of the anisotropic dielectric cylinder on the electromagnetic scattering characteristics is analyzed.The calculation results obtained by this method are compared with those obtained by the electromagnetic simulation software FEKO,which have good consistency and great advantages in calculation time.This solution process can reduce the amount of calculation and increase the iteration speed when it is used to solve related backscattering problems.