Solution of time-harmonic Maxwell's equations by a domain decomposition method based on PML transmission conditions

Numerical discretization of the large-scale Maxwell's equations leads to an ill-conditioned linear system that is challenging to solve. The key requirement for successive solutions of this linear system is to choose an efficient solver. In this work we use Perfectly Matched Layers (PML) to increase this efficiency. PML have been widely used to truncate numerical simulations of wave equations due to improving the accuracy of the solution instead of using absorbing boundary conditions (ABCs). Here, we will develop an efficient solver by providing an alternative use of PML as transmission conditions at the interfaces between subdomains in our domain decomposition method. We solve Maxwell's equations and assess the convergence rate of our solutions compared to the situation where absorbing boundary conditions are chosen as transmission conditions

Monitoring of the heart movements using a FMCW radar and correlation with an ECG

Monitoring the heart activity is an important task to prevent and diagnose cardiovascular diseases. An electrocardio-gram (ECG) is the gold standard for such task. It monitors the heart electrical activity, and while the later is highly correlated to the cardiac mechanical activity, it does not provide all the information. Other sensors such as echo-cardiograph allow to monitor the heart movements, but such tools are hard to operate and expensive. Therefore, contact-less monitoring of the heart using RF sensing has gained interest over the past years. In this paper, we provide a process to extract the movement of the heart with a high accuracy from a millimeter wave radar, i.e. we describe a non invasive and affordable way to monitor cardiac movements. We then demonstrate the correlation between the observed movements and the ECG. Furthermore, we propose an algorithm to synchronize the ECG signal and the processed signal from the radar sensor. The results we obtained provide insights on the mechanical activity of the heart, which could assist cardiologists in their diagnosisComment: 10 pages, 19 figure

Physical Contamination Detection in Food Industry Using Microwave and Machine Learning

The detection of contaminants in food products after packaging by a non-invasive technique is a serious need for companies operating in the food industry. In recent years, many technologies have been investigated and developed to overcome the intrinsic drawbacks of the currently employed techniques, such as X-rays and metal detector, and to offer more appropriate solutions with respect to techniques developed in the academic domain in terms of acquisition speed, cost, and the penetration depth (infrared, hyperspectral imaging). A new method based on MW sensing is proposed to increase the degree of production quality. In this paper, we are going to present a novel approach from measurements setup to a binary classification of food products as contaminated or uncontaminated. The work focuses on combining MW sensing technology and ML tools such as MLP and SVM in a complete workflow that can operate in real time in a food production line. A very good performance accuracy that reached 99.8% is achieved using the non-linear SVM algorithm, while the accuracy of the performance of the MLP classifier reached 99.3%

Numerical Modeling and High Speed Parallel Computing: New Perspectives for Tomographic Microwave Imaging for Brain Stroke Detection and Monitoring

This paper deals with microwave tomography for brain stroke imaging using state-of-the-art numerical modeling and massively parallel computing. Microwave tomographic imaging requires the solution of an inverse problem based on a minimization algorithm (e.g. gradient based) with successive solutions of a direct problem such as the accurate modeling of a whole-microwave measurement system. Moreover, a sufficiently high number of unknowns is required to accurately represent the solution. As the system will be used for detecting the brain stroke (ischemic or hemorrhagic) as well as for monitoring during the treatment, running times for the reconstructions should be reasonable. The method used is based on high-order finite elements, parallel preconditioners from the Domain Decomposition method and Domain Specific Language with open source FreeFEM++ solver

Detection of brain strokes using microwave tomography

Brain stroke is a major cause of disability and death worldwide. There are two types of stroke, ischemic or cerebral infarction (85% of cases) and hemorrhagic (15%). The diagnosis must be made quickly (within 3 to 4 hours after the onset of symptoms) to determine the nature of the stroke and proceed to treatment. Recent works have shown the modification of the complex permittivity according to the nature of stroke [1] in the microwave domain. We are interested here in the detection of brain strokes using microwave tomography. We present results obtained by electromagnetic simulations coupled to a realistic noise model of measurements. The forward problem is based on a massively parallel computing using domain decomposition method, and an inverse problem based on L-BFGS algorithm with a regularization based on total variation (TV)

Whole-microwave system modeling for brain imaging

In this paper, we present the results of a whole-system modeling of a microwave measurement prototype for brain imaging, consisting of 160 ceramic-loaded antennas working around 1 GHz. The modelization has been performed using open source FreeFem++ solver. Quantitative comparisons were performed using commercial software Ansys-HFSS and measurements. Coupling effects between antennas are studied with the empty system (without phantom) and simulations have been carried out with a fine numerical brain phantom model issued from scanner and MRI data for determining the sensitivity of the system in realistic configurations

Développement d'antennes millimétriques en bande W

The following manuscript describes the 5 years work dedicated to the developments of mm-Wave antennas, more specifically in the W-band. The basic motivation is the increasing interest for using millimetre waves in civil applications, specially in the radar field. Reflecatarrays are good candidates for these applications. Nevertheless, specific simulation/ modelisation tools and measurements setups have to be developed. The manuscript is organised as follows: - Chapter one describes the printed reflector antennas developed a multi-sensor system on rescue helicopter. Antennas are part of a radar operating at 94 GHz. Tests including in-flight measurements were conducted. - Chapter 2 is dedicated to dielectric lenses and reflectarrays studies. - Chapter 3 describes the antenna measurement setup and a lens-based CATR study. - Chapter 4 is dedicated to old studies conducted in X and C bands on uniplanar Vivaldi antennas.Le travail présenté dans ce mémoire de HDR porte sur le développement d'antennes millimétriques en bande W. Ces dernières succientent un regain d'intérêt suite à l'émergence des applications civiles en gamme millimétrique, notemment dans le domaine des radar. Concevoir de telles antennes, de type reflectarray, implique non seulement le développement d'outils de simulation/modélisation spécifiques mais aussi la mise en place de dispositifs de mesures adaptés. Le manuscrit s'articule autour de axes de recherche: - le premier chapitre présente les principaux résultats obtenus dans le cadre des antennes millimétriques pour radar embarqués, - le second chapitre décrit les études relatives aux réseaux réflecteurs et lentilles diélectriques, - le troisième chapitre est consacré à la métrologie des antennes avec la mise en place du système de mesure en bande millimétrique et l'étude d'une base compacte, - le quatrième et dernier chapitre est la synthèse des travaux menés entre 1996 et 2001 sur les structures planaires pour l'insertion de fonctions actives

Radar de détection de petits objets au sol (vers un système d'imagerie millimétrique)

Les systèmes millimétriques ont connu un regain d intérêt durant les dix dernières années, pour des applications grand public visant à améliorer le confort et la sécurité des usagers tels que les radars automobiles à 77 GHz. De tels radars sont équipés d antennes qui doivent posséder à la fois un faisceau étroit afin d obtenir une bonne résolution latérale, et une bande passante relativement élevée pour augmenter la résolution en portée du radar. Actuellement celle-ci est de 200 à 250 m bien que de récents projets aient conduits à détecter des cibles bien plus lointaines grâce à l augmentation de la puissance incidente et du gain des antennes. Les récents progrès des circuits et composants permettent à présent d envisager de nouvelles applications. La thèse proposée porte sur l étude d un système permettant de détecter toutes sortes d objets au sol. Une application envisagée est la détection de débris présents sur les pistes des aéroports. L exemple le plus frappant qui démontre l utilité d un tel système, est l accident survenu au Concorde il y a plusieurs années causé par un débris métallique présent sur la piste de décollage. Un radar d imagerie fonctionnant dans la gamme millimétrique devrait être capable de détecter de petits objets en métal, en béton, en pierre ou même en plastique. En s appuyant sur les fréquences allouées par les autorités compétentes, les recherches précédentes et la disponibilité sur le marché des composants et circuits intégrés, la gamme de fréquences comprise entre 76 et 81 GHz est retenue. Un système antennaire complexe reposant sur l utilisation d un réseau réflecteur à diagramme d élévation en cosécante carrée et directif en azimut est développé.In the last decade, microwave and millimeter-wave system have found u=increasing commercial applications and gained importance in comfort and security applications like in automotive radar sensors in the 77 GHz frequency range. Such sensors are equipped with narrow beam antennas for a good lateral resolution and a reasonably high bandwidth for a high range resolution. Detection range for automotive applications presently is 200-250 m, but in some projects much higher detection distances have been demonstrated with increased transmitter power and higher gain antennas. Due to an increasing maturity and availability of circuits and components for such systems, other applications are within the range of realization. In the proposed thesis, sensor systems, for obstacle objects on the ground shall be investigated. A possible application is the debris detection on airport runways. A basic motivation for this is the fatal accident with a Concorde aircraft a few years ago due to a metal part lost by an aircraft on the runway some time before. An imaging radar sensor at sufficiently high frequency shall be able to detect relatively small pieces of metal, concrete, stone, or even plastic on an otherwise quite flat surface. Based on frequency range between 76 GHz and 81 GHz is selected for the investigations. A complex antenna system is developed. It is based on the use of a reflect array with a squared cosecant beam in elevation and a focused one in azimuth.NICE-BU Sciences (060882101) / SudocSudocFranceF

Étude d'une base compacte millimétrique à lentille diélectrique

NICE-BU Sciences (060882101) / SudocSudocFranceF

Millimeter-Wave Imaging for FOD Detection

International audienceWe present an efficient approach to reconstruct images of small objects and Foreign Object Debris (FODs) from scattered field synthetic data and measurements in W-band (75-110 GHz), taking advantages of spatial and polarization diversities, and processed with either qualitative or quantitative inverse methods. The target application is FOD detection for airport runways. Most existing systems are monostatic but rapid advances in millimeter-wave technologies make it realistic to imagine the deployment of multistatic radars on either side of airport runways. In the following, we investigate the contribution of multistatic measurements, on the reconstruction of typical debris, courtesy of DGAC (French Civil Aviation)