A mixed order BCGS-FFT based fast 3D inverse electromagnetic scatterings for anisotropic objects

The purpose of the electromagnetic (EM) inverse scattering problems is to estimate EM properties of unknown objects within area of interest with known scattered EM fields. Three dimensional inverse scattering problems can be conveniently modeled by volume equivalence theorem. The volume equivalence theorem describes the forward scattering problems by volume integral equations. Estimating unknown EM properties of objects from these volume integral equations is a nonlinear problem. The born iterative method (BIM) and the distorted born iterative method (DBIM) are proposed to efficiently solve the nonlinear problems (Y.M. Wang and W.C. Chew Int. Jour. Imaging Sys. Tech. 1, 100-108, 1989). The BIM is more stable with noisy data and the DBIM converges faster.