요한요소법과 LMA-GA 혼합법을 이용한 거대 강산란체의 역산란 = Inverse Scattering of High contrast and Large Object using Finite Element Mehtod and Hybrid LMA-GA

다국어 초록 (Multilingual Abstract)

An iterative inverse scattering method(IISM) for reconstructing the permittivity of two dimensional high contrast and large object is presented. This method uses the finite element method(FEM) for calculating the scattering fields and the hybrid method for minimizing the cost function. The FEM calculates the scattered fields faster than the method of moment(MM). The hybrid method(HLMGA) is composed of a Levenberg-Marquardt algorithm(LMA) and a genetic algorithm(GA). Numerical results show that the IISM based on the HLMGA and GA can always reconstruct all the permittivity profiles of a high contrast and large object, in contrast the IISM based on the LMA often converges to the local minima of the cost function. The HLMGA gives better permittivity profiles and faster convergence than the GA. When the noise is presented in the scattering fields, the characteristics of the cost function show that multiple incident waves are needed for the stable inversion. Also both LMA and a prior knowledge of background medium for a fast convergence are used. The permittivity profile converged to local minima by LMA is modified by substituting the background profile into a known background medium, then this modified profile as an initial one in order to get out of a local minima of cost function is used.