Passive RFID System for Object Shape Estimation

European Conference on Antennas and Propagation (12th, 2018, London

Novel Inverse-Scattering Methods in Banach Spaces

The scientific community is presently strongly interested in the research of new microwave imaging methods, in order to develop reliable, safe, portable, and cost-effective tools for the non-invasive/non-destructive diagnostic in many fields (such as medicine, civil and industrial engineering, \u2026). In this framework, microwave imaging techniques addressing the full three-dimensional nature of the inspected bodies are still very challenging, since they need to cope with significant computational complexity. Moreover, non-linearity and ill-posedness issues, which usually affects the related inverse scattering problems, need to be faced, too. Another promising topic is the development of phaseless methods, in which only the amplitude of the electric field is assumed to be measurable. This leads to a significant complexity reduction and lower cost for the experimental apparatuses, but the missing information on the phase of the electric field samples exacerbates the ill-posedness problems. In the present Thesis, a novel inexact-Newton inversion algorithm is proposed, in which the iteratively linearized problems are solved in a regularized sense by using a truncated Landweber or a conjugate gradient method developed in the framework of the l^p Banach spaces. This is an improvement that allows to generalize the classic framework of the l^2 Hilbert spaces in which the inexact-Newton approaches are usually defined. The applicability of the proposed imaging method in both the 3D full-vector and 2D phaseless scenarios at microwave frequencies is assessed in this Thesis, and an extensive validation of the proposed imaging method against both synthetic and experimental data is presented, highlighting the advantages over the inexact-Newton scheme developed in the classic framework of the l^2 Hilbert spaces

Inverse Scattering for Monochromatic Phaseless Measurements

International audienceAn inverse method and measurement setup for profile and constitutive parameters reconstruction from monochromatic phaseless information is presented. The method is based on the minimization of a cost function that relates the measured field with the one scattered by a model of the object under test (OUT), where the position, contour, and constitutive parameters are the unknowns. As a result, phaseless information is directly related to the inverse problem unknowns, thus avoiding the need of an intermediate phase retrieval step. Due to the nonlinear nature of the cost function, global optimization techniques, such as the particle swarm optimization and differential evolution algorithms, have been considered for cost function minimization. An exhaustive analysis of the cost function behavior as a function of the electric size of the OUT is presented, discussing the optimal OUT size where the proposed methodology provides accurate profile and constitutive parameters reconstruction. The proposed methodology is conceived to use it together with a simple, low-cost measurement setup for fast characterization of perfect electric conductor and dielectric objects. Measurement examples are presented aiming to prove the feasibility of the described measurement setup