Nonlinear inversions of immersed objects using laboratory-controlled data

Abstract

The paper is focused on the characterization of objects immersed in water using laboratory-controlled data obtained in the microwave frequency range. Experiments performed at the laboratory represent, at a reduced scale, the electromagnetic characterization of objects buried at a shallow depth in the sea, with the objects and the emitting and receiving antennas being immersed. Characterization is taken here as an inverse scattering problem whose data, whilst limited in aspect, consist of the values of the time-harmonic scattered electric fields measured at several discrete frequencies on a single line of a few receivers. The modelling of the wave–object interaction is performed through a domain integral representation of the fields in a two-dimensional transverse-magnetic configuration. The inverse scattering problem is solved by means of two iterative algorithms tailored for homogeneous objects: the so-called level-set method and a binary specialized contrast source inversion method. Emphasis is put both on the experimental features and their modelling, and the results obtained for different types of objects are presented.