Hybrid scheme for inverse scattering of electrically large regions

An efficient algorithm is presented for two-dimensional inverse scattering from electrically large regions. The technique is a hybrid combination of the modified-gradient (MG) method and a beam-tracing-based iterative Born method. The beam-tracing-based inversion cannot resolve sharp contrasts, but such are subsequently recovered by the MG algorithm. In particular, the hybrid scheme feeds the iterative Born reconstructed profile as the initial guess to the modified-gradient algorithm. The hybrid scheme has a highly improved convergence rate and also overcomes the limitations of the iterative Born and modified-gradient schemes, when each is applied alone. Results are presented for several lossless profiles. Issues addressed include the types of profiles that can be successfully imaged, the range of parameters over which the scheme is effective, and performance when noisy data are considered.