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

Microwave Imaging of 3D Dielectric Structures by Means of a Newton-CG Method in Spaces

An increasing number of practical applications of three-dimensional microwave imaging require accurate and efficient inversion techniques. In this context, a full-wave 3D inverse-scattering method, aimed at characterizing dielectric targets, is described in this paper. In particular, the inversion approach has a Newton-based structure, in which the internal linear solver is a conjugate gradient-like algorithm in lp spaces. The presented results, which include the inversion of both numerical and experimental scattered-field data obtained in the presence of homogeneous and inhomogeneous targets, validate the reconstruction capabilities of the proposed technique

Hemorrhagic brain stroke detection by using microwaves: Preliminary two-dimensional reconstructions

Preliminary numerical results concerning the application of a Gauss-Newton method for diagnostic purposes of hemorrhagic brain strokes are reported. Interrogating microwaves are used in a multistatic and multiview arrangement. The reported results concern a two-dimensional model under transverse magnetic illumination conditions

Nonlinear electromagnetic inverse scattering in via Frozen or Broyden update of the Fr\ue9chet derivative

Microwave imaging methods are useful for non-destructive inspection of dielectric targets. In this work, a numerical technique for solving the 3D Lippmann-Schwinger integral equation of the inverse scattering problem via Gauss-Newton linearization in Banach spaces is analysed. More specifically, two different approximations of the Fr\ue9chet derivative are proposed in order to speed up the computation. Indeed it is well known that the computation of the Fr\ue9chet derivative is generally quite expensive in three dimensional restorations. Numerical tests show that the approximations give a faster restoration without loosing accuracy

Three-dimensional microwave imaging in Lp Banach spaces: Numerical and experimental results

In this paper, a microwave imaging method able to inspect three-dimensional configurations is proposed. The approach is developed in Lp Banach spaces, and allows to suitably face the ill-posedness of the considered full vector inverse scattering problem. The assumed nonconventional spaces require several modifications in the original inexact-Newton scheme, which give rise to a significant improvement in reducing the oversmoothing effects in the reconstructed distributions of the dielectric properties of the targets. The proposed approach is discussed in details and validated by using both numerical simulations and real data

A three-dimensional microwave imaging approach based on a Lp Banach space inversion procedure

A three-dimensional microwave imaging inversion algorithm is proposed in this paper. The developed approach is based on an efficient procedure, performing a regularization in the framework of the Lp functional Banach spaces. In order to increase the computational efficiency of the method, two specific speed-up strategies have been developed. The performances of the method have been preliminarily assessed by means of numerical simulations

Cost-efficient FMCW radar for multi-target classification in security gate monitoring

A prototype of a radar system for classification of multiple targets passing through a road gate is presented in this paper. It allows to identify different types of targets, i.e., pedestrians, motorcycles, cars, and trucks. The developed system is based on a low-cost 24 GHz off-the-shelf FMCW radar, combined with an embedded Raspberry Pi PC for data acquisition and transmission to a remote processing PC, which take care of detection and classification. The processing chain relies upon a tracking algorithm to follow the targets during traversal, combined with a classification scheme based on support vector machines. The approach has been validated with experimental data acquired in different scenarios, showing good identification capabilities

Advanced Real-Time Monitoring of Rainfall Using Commercial Satellite Broadcasting Service: A Case Study

Correct regulation of meteoric surface and subsurface flow waters is a fundamental goal for the sustainable development of the territories. A new system, aimed at real-time monitoring of the rainfall and of the cumulated rainfall, is introduced and discussed in the present paper. The system implements a Sensor Network based on the IoT paradigm and can cover safety-critical \u201chot spots\u201d with a relatively small number of sensors, strategically placed, in areas not covered by traditional weather radars and rain gauges, and lowering the costs of deployment and maintenance with respects to these devices. A real application case, based on the implementation of the pilot plant at the Monte Scarpino landfill (Genoa, Italy), is presented and discussed. The system performances are assessed on the basis of comparisons with data provided by a polarimetric weather radar and by a traditional rain gauge. View Full-Tex