Terahertz Imaging Theory And The Application Of Finite-Difference Time-Domain Method In It

Terahertz technology is increasingly valued by people,and its various characteristics make it have great scientific value and a wide range in object imaging,environmental monitoring,medical diagnosis,radio astronomy,broadband mobile communications,especially satellite communications and military radar.Application prospects.Among these,imaging is another important application aspect.And related to it,electromagnetic inverse scattering problem is even more important.However,since measurement data can only be obtained from a limited area,electromagnetic backscattering is a challenging and ill-posed problem.Nonlinearity and morbidity are two of the major difficulties.So far,no universal solution has been formed.The common approach is to use linearization approximation and iterative methods to deal with nonlinear problems,and to use regularization techniques to suppress pathological characteristics.In this paper,we first study the basic theory of finite difference time domain methods,including numerical dispersion,numerical stability,and various boundary conditions.Then,for the nonlinear and ill-posed problems of the inverse problem,the Born approximation and the Rytov approximation are used to solve the nonlinearity and the Tikhonov regularization to suppress the ill-posed problem.Finally,a method is proposed in this paper.The finite-difference time-domain method is used in the GNI method.The time domain finite-difference method is used to solve the positive problem in the electromagnetic inverse scattering problem.The total time-domain field can be used to calculate Green's function.When solving the inverse problem,this paper selects the GNI method and decomposes the original problem into two subproblems for solving the GN direction and the step length.By solving these two subproblems,the reconstruction is realized.Through simulation,it is found that the method has certain feasibility.