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 transversemagnetic 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.

On the Calibration of a Multistatic Scattering Matrix Measured by a Fixed Circular Array of Antennas

“…One way is to construct it mechanically by moving physically the emitters and the receivers all around the illuminated zone. This is what has been done in a free space environment [3][4][5], in a liquid environment [6,7] or above a buried target [8,9] for example. Another possibility is to construct it electronically with a fixed array of antennas, each pair of emitter/receiver being selected thanks to hyperfrequency switches or any kind of multiplexer/demultiplexer devices, e.g., [10][11][12][13][14][15].…”

GPR Estimation of the Geometrical Features of Buried Metallic Targets in Testing Conditions

“…Also in this case, the inversion model is concerned with an investigation domain similar to that already presented. Again, the measurement configuration assumes a bistatic modality with the source and receiver separated by 19 The first tomographic reconstruction from measured data is shown in Fig. 10 and is referred to the case of a pair of metallic targets already presented in Fig.…”

“…These conditions are difficult to be achieved in a large test site (see, e.g., [17,18] and the literature therein) but can be obtained in laboratory scale experiments [14,[19][20][21].…”

Bayesian inversion for optical diffraction tomography

“…The variables w and s are initialized as follows: the initial estimate of the sources is obtained by back-propagating the scattered field data from S onto D [37]:…”