Inversion of experimental data using linearized and binary specialized nonlinear inversion schemes

We deal with an electromagnetic inverse scattering problem where the goal is to characterize dielectric and metallic unknown targets from measurements of the scattered electric fields that result from their interaction with a known interrogating wave in the microwave frequency range. This nonlinear and ill-posed inverse problem is tackled from experimental data collected in a laboratory-controlled experiment led at the Institut Fresnel. Inversion is performed by means of the binary modified gradient method, a nonlinearized iterative technique tailored to the case of homogeneous targets. This method does not always converge towards an acceptable solution if initialization of the unknowns is not carefully performed. The latter is obtained, herein, from diffraction tomography, a linearized solution method which yields in a very fast way a rough estimate of the location, shape and size of the unknown target.