Study And Application On Precorrected-FFT Method In Analysis Of EM Scattering

The fast analysis of electromagnetic scattering characteristic of targets plays an important role in the technical areas of radar detection, radar target identification and radar cloaking and anti-cloaking. It has been a hot research topic to analyze the electromagnetic scattering from complex targets that compose of arbitrary metal and dielectric, partly because more and more composite materials are used in more and more targets and equipments. Aiming at these backgrounds, with the electromagnetic field integral equations being used as theoretical basis and the method of moments being used as solving technique the precorrected-FFT method is employed to accelerate the solving process in this thesis. The primary research focuses on studying some key problems of the precorrected-FFT method, improving the method, and applying the method to the fast analysis of EM scattering characteristics of complex targets.This thesis is made up of three parts. The first part of this thesis focuses on studying the basic theory and the specific implementation to solve electromagnetic field integral equations with method of moments. The second part focuses on applying the precorrected-FFT method to analyze metallic objects, dielectric objects, and composite metallic-dielectric objects based on its principle and implementation. In the third part, the multilevel precorrected-FFT method is presented and implemented to overcome the intrinsic drawback of the precorrected-FFT method, and then the performances of both methods are compared.In the first part of this thesis, the electromagnetic field integral equations are deduced from the basic electromagnetic theory firstly. Then the basic ideas and the general process of solving the integral equation with method of moments are introduced. And then the RWG basis function for metallic objects and SWG basis function for dielectric objects are constructed. Finally, the specific processes of the discretization of the surface integral equation of metallic objects with RWG basis function, the discretization of the volume integral equation of dielectric objects with SWG basis function, and the discretization of the volume-surface integral equation of composite metallic-dielectric objects with RWG and SWG basis functions are explained in detail, as well as the resulting linear equations.In the second part of this thesis, the basis ideas, the general process, the theory foundation and the implementation of the operators of the precorrected-FFT method are set forth firstly. Then a new stencil topology is implemented to reduce the memory requirement of near-zone precorrections. Finally, the precorrected-FFT method is applied to analyze the RCSs of metallic objects, dielectric objects and composite metallic-dielectric objects, with its accuracy, memory requirement and computation complexity being investigated. In the last part of this thesis, the multilevel precorrected-FFT method is presented to overcome the poor efficiency of the precorrected-FFT method when analyzing metallic objects, hollow dielectric objects and composite metallic-dielectric objects. Then an improved stencil topology and the multilevel stencil structure adapted to the multilevel precorrected-FFT method are constructed. And then the inter-level operators such as projection, interpolation and precorrection are implemented. And then the accuracy, memory requirement and computation complexity of the multilevel precorrected-FFT method are investigated in combination with the analysis of various objects. Finally, the multilevel precorrected-FFT method is applied to analysis the RCSs of various objects, followed by the range of application of the multilevel precorrected-FFT method and the range of application of the precorrected-FFT method being compared.