The method of decomposition the time reversal operator has been introduced with aim focusing acoustic waves on a selected target. It is based derivation invariants operator, which linked to transfer matrix array transducers insonifying invariant scattering medium. theoretical and numerical results concern independent point-like scatterers. Here, we apply numerically same technique electromagnetic waves, all interactions between various scatterers are taken into account. This may be very...

We present a 3D spherical bistatic experimental setup developed in the anechoic chamber of Institut Fresnel Marseille, France, for scattering measurements targets microwave domain, both copolarization and cross‐polarization. first describe geometry setup, measurement protocol, calibration process. The results obtained different metallic dielectric are then compared to numerical simulations, computed either using coupled dipole method or Mie theory. These comparisons used validate algorithms...

A two-step electromagnetic detection procedure is proposed to characterize a dielectric obstacle buried at low depth under rough surface from single-frequency and multistatic data. First, we have developed, in the framework of small perturbation theory, correlation scattered field, which enables us recover an estimation roughness profile. This method tested for various cases with synthetic data provided by rigorous boundary integral solver. Second, obtained profile introduced into numerical...

An accurate knowledge of the complex permittivity value materials is compulsory when performing experimental electromagnetic applications. Unfortunately, these values are not so obvious to determine in practice. In this letter, we propose a novel approach for determining dielectric constant materials. This method combines free-space far-field scattering pattern measurements with Bayesian procedure, which fully exploits measurement uncertainties. Therefore, measured weighted according their...

The calibration of the multistatic scattering matrix plays an important part in construction a quantitative microwave imaging system.For measurement applications, must be performed on amplitude and phase fields interest.When antennas are not completely identical, as for example with multiplexed array, specific procedure constructed.In present work, we explain how complex can defined which takes advantage geometrical organization antennas.Indeed, arrays positioned circle, inherent symmetries...

This letter deals with the monitoring of volumetric water content a soil column in fully controlled environment by means noninvasive microwave imaging system. Indeed, moisture is an important piece information to improve fluid flow modeling or better understand uptake plant roots. In this letter, we address problem recovering footprint evolution respect time using built-in laboratory setup coupled robust qualitative method: linear sampling method (LSM). The ruled Richards equations and...

To overcome the ill-posedness of inverse scattering problem, we introduce an appropriate way representing unknown permittivity profile which benefits from two a priori pieces information are commonly encountered. First, map has limited spatial support can be contained within circular investigation area. Second, physical reasoning based on operator, there is only number independent parameters that retrieved measured fields. Both adequately introduced by in terms Zernike polynomial expansion,...

The spatial depolarization of light emitted by heterogeneous bulks is predicted with exact electromagnetic theories. sample microstructure and geometry connected partial polarization.

This article deals with the inverse scattering problem from scattered field data measured inside a closed microwave scanner. system is presently being developed to demonstrate potentiality of non-invasive imaging for volumetric water content monitoring. The final goal retrieve soil moisture information as it an important parameter understanding fluid flow modelling, well uptake by plants roots. Based on actual state setup, we are proposing appropriate numerical tools, in particular finite...

The electromagnetic dual-primal finite element tearing and interconnecting (FETI-DPEM) method is a nonoverlapping domain decomposition developed for the analysis of large-scale problems, where corner edges are globally numbered. This paper presents an extension FETI-DPEM2 method, named FETI-full dual primal (FETI-FDP2), more flexible Robin-type boundary conditions imposed, on inner interfaces between subdomains as well edges, leading to new interface problem. Its capacities tested in...

A study using tunneling spectroscopy of the density states in vicinity Fermi level has been performed on ${\mathrm{NbSe}}_{3}$ at low temperature. The conductance data reveal an asymmetry with respect to and below 4.2 K two minima. These results definitely establish semimetallic character Tunneling spectra have analyzed assuming anisotropic gap structure, transverse coupling energy derived is good agreement band calculations.

Context. The growth of dust grains in protoplanetary disks is not understood detail. Several studies have proposed the presence aggregates and irregular to overcome physical barriers grain models. In order understand scattering properties these aggregates, laboratory measurements light microwave been developed over last 50 years. Aims. We aim measure different analog with fractal dimensions 1.5, 1.7, 2.0, 2.5, 2.8. Methods. used technique (microwave analogy) for measurements. particles were...

In this letter, we focus on an imaging procedure that retrieves the complex permittivity map of investigation domain from electromagnetic scattered field measurements. The transmitter and receiver are independently moved along two parallel lines finite extent. such a configuration, antenna effects drastic importance. We propose thus quantitative modeling antennas does not require additional calibration process. model is completely incorporated in inversion allows to recover tubes whose...

ABSTRACT Probing the near‐subsurface in presence of absorbing media is a very challenging problem. Within that framework, we analyse capabilities mono‐frequency/multistatic set‐up for detecting shallowly buried targets. As antennas constitute an important part probing device, accurate method modelling behaviour proposed. This modelling, performed thanks to correct balanced set elementary sources, then incorporated calculation scattered field, with home‐made Finite Element Method software....

A Quasi-Newton method for reconstructing the constitutive parameters of three-dimensional (3D) penetrable scatterers from scattered field measurements is presented. This adapted handling large-scale electromagnetic problems while keeping memory requirement and time flexibility as low possible. The forward scattering problem solved by applying finite-element tearing interconnecting full-dual-primal (FETI-FDP2) which shares same spirit domain decomposition methods finite element methods. idea...

In this paper, we address the problem of reconstruction shape a 3D perfectly conducting object. This object is assumed to be immersed in homogeneous lossy embedding medium cross borehole configuration. The method based on an optimization process performed with help conjugate gradient method. A boundary integral formalism and adjoint state are used order compute field scattered by estimated its derivatives respect small deformations shape. paper also extend case regularization which optimize...

This paper deals with the detection of a buried object beneath rough surface in two-dimensional configuration. A new method for detecting objects from wide-band, near-field, multi-static data is suggested. The so-called near-field configuration corresponds to set transmitters and receivers located along line segment vicinity surface. proposed here based on correlation scattered fields two sets associated transmitters. theoretical study framework low-frequency approximation predicts an...

In this work, we present an extension of the classical DORT method for time-harmonic inverse medium scattering problems. This tool enables one to estimate shape unknown scatterers even if they are not necessarily point-like scatterers. is described and compared with existing sampling methods. Moreover, a mathematical derivation provided its validation, either in free-space environment or metallic enclosure setup. Two-dimensional examples, based on measured data sets acquired circular...

In this paper we present our advances in the scattering measurement of low electromagnetic signature objects. The targets under test are spheroids relative permittivities and sizes comparable to wavelength. measurements were carried-out at experimental facility "Centre Commun de Ressources en Microondes" (CCRM) a bistatic configuration using hard gating noise reduction system. further assessed through comparisons computations obtained with Finite Element Method code. Thanks careful control...

A numerical study of second-harmonic generation (SHG) in cavity resonator integrated grating filters (CRIGFs) shows extraordinary strong conversion rates planar corrugated waveguides based on lithium niobate layers, not exceeding 625 µm length. The key idea is to couple the dark mode structure at pump frequency that has a Q-factor much stronger than bright commonly used. This achieved by shifting coupler between enclosing Bragg mirrors, resulting an asymmetric structure. Three structures are...

Due to the increasing number of applications in engineering design and optimization, more attention has been paid full-wave simulations based on computational electromagnetics.In particular, finite-element method (FEM) is well suited for problems involving inhomogeneous arbitrary shaped objects.Unfortunately, solving large-scale electromagnetic with FEM may be time consuming.A numerical scheme, called dual-primal finite element tearing interconnecting (FETI-DPEM2), distinguishes itself...

This letter considers the problem of detecting and characterizing a target buried beneath rough surface separating two homogeneous half spaces. The is tackled by analyzing frequency-averaged Wigner-Ville function, purpose which to filter out scattering. Characterization performed using iterative solution derived from Newton-Kantorovitch algorithm as applied function instead scattered field usually done. In addition, scattering model involved in inversion scheme assumes flat interface,...