1,721,087 research outputs found
Etude de métamatériaux à indice de réfraction négatif
No full text1 Volume; Diffusion restreinte; 87 page
Towards new prospects for electromagnetic compatibility, in Metamaterials and Wave Control, Eric Lheurette (ed)
No full textThis chapter focuses on the potential of metamaterials in EMC applications. It is organized as follows. In section 4.2, a short overview of electromagnetic compatibility is given. To highlight the relevance of metamaterials in EMC problems, current trends in industrial applications as well as the consequent challenges arising in EMC are described. The cases of transport and telecommunications industries are considered. The two main applications foresighted are filtering and shielding. Section 4.3 focuses on electromagnetic shielding. The performance of shields depends on both their geometric and electrical parameters, and on the characteristics of the incident EM field. Figures of merit to evaluate these performances are given. Examples of three published one-dimensional metamaterial shields based on reflection or absorption are given. In section 4.4, a detailed analysis of a three-dimensional metamaterial cavity is proposed. The contribution of metamaterials highlighted in the concept of subwavelength cavities. The design steps of an appropriate metamaterial for this particular application are given. Finally, the metamaterial designed are applied to the walls of a regular reverberation chamber generally used for EMC tests
Etude de métamatériaux à indice de réfraction négatif
No full text1 Volume; Diffusion restreinte; 87 page
Etude de métamatériaux à indice de réfraction négatif
No full text1 Volume; Diffusion restreinte; 87 page
Antenne multimode, multiport et multistandard pour système de communication adaptable
No full textAntenne multimode, multiport et multistandard pour système de communication adaptable Une antenne multimode, multiport et multistandard comprenant un substrat sur lequel est disposé un unique élément rayonnant planaire, une pluralité de ports de communication connectés à l’élément rayonnant chacun à un emplacement distinct de l’élément rayonnant et destinés à être couplés à différents moyens de communication à la fois utilisant différents standards de communication. L’élément rayonnant comprend une forme elliptique. Brevet déposé sous les numéros EP4165727A1;FR3111480A1
Towards new prospects for electromagnetic compatibility, in Metamaterials and Wave Control, Eric Lheurette (ed)
No full textThis chapter focuses on the potential of metamaterials in EMC applications. It is organized as follows. In section 4.2, a short overview of electromagnetic compatibility is given. To highlight the relevance of metamaterials in EMC problems, current trends in industrial applications as well as the consequent challenges arising in EMC are described. The cases of transport and telecommunications industries are considered. The two main applications foresighted are filtering and shielding. Section 4.3 focuses on electromagnetic shielding. The performance of shields depends on both their geometric and electrical parameters, and on the characteristics of the incident EM field. Figures of merit to evaluate these performances are given. Examples of three published one-dimensional metamaterial shields based on reflection or absorption are given. In section 4.4, a detailed analysis of a three-dimensional metamaterial cavity is proposed. The contribution of metamaterials highlighted in the concept of subwavelength cavities. The design steps of an appropriate metamaterial for this particular application are given. Finally, the metamaterial designed are applied to the walls of a regular reverberation chamber generally used for EMC tests
Amélioration des performances des antennes intégrées à l'aide de métamatériaux et de la théorie des modes caractéristiques
No full textLa demande de systèmes sans fil mobiles miniaturisés a accru le besoin d'intégrer des antennes électriquement petites qui se caractérisent généralement par de mauvaises performances et un faible rendement. Des approches telles que l'utilisation de diélectriques, de fentes, de composants parasites,… ont été appliquées au fil des années pour améliorer les performances de telles antennes. La plupart des méthodes existantes sont empiriques et basées sur des optimisations chronophages. D'autres approches comme l'optimisation du courant d'antenne basée sur l'analyse modale sont des approches systématiques qui ont été proposées. Il a également été montré que l'utilisation de matériaux artificiels appelés inclusions de métamatériaux comme élément parasite permet d'améliorer les performances de l'antenne à moindre coût. Cependant, le choix de la bonne inclusion pour une conception d'antenne est compliqué, en particulier lorsque l'antenne est non canonique et arbitraire.Dans cette thèse, nous proposons une méthode systématique pour améliorer les performances de l'antenne en utilisant l'inclusion de métamatériaux. La méthode est utilisée pour concevoir une antenne inspirée des métamatériaux avec le potentiel d'analyser à la fois les propriétés de rayonnement et de diffusion de la conception inspirée des métamatériaux. Il utilise l'approche modale caractéristique pour évaluer l'énergie quantitative stockée des inclusions de métamatériaux qui fournissent des informations quantitatives sur le comportement en champ proche de l'inclusion. L'approche modale de l'énergie stockée est comparée à l'approche des paramètres efficaces pour décrire les inclusions et elles montrent toutes deux une bonne concordance qualitative. Dans le processus de conception inspiré des métamatériaux, un mode caractéristique est appliqué pour obtenir un aperçu des propriétés de rayonnement de la structure et l'inclusion est choisie pour compenser l'énergie stockée de l'élément d'antenne en fonction de sa quantité d'énergie stockée modale. Le couplage entre l'antenne et l'inclusion est analysé en utilisant le coefficient de couplage intermodal. Il représente la diffusion entre l'antenne et l'inclusion et définit comment la distance de positionnement et de séparation entre les deux éléments affecte les performances globales du système inspiré des métamatériaux. La méthodologie proposée est validée avec un prototype qui montre une bonne concordance entre le résultat simulé et mesuré. La méthode proposée est en outre appliquée dans l'analyse de l'amélioration de l'antenne intégrée en utilisant le camouflage électromagnétique. Le manteau se couple à l'élément dans son voisinage et permet à l'élément d'antenne actif de fonctionner avec un meilleur rendement de rayonnement. La méthode proposée est donc diverse et utile pour la conception future de systèmes inspirés des métamatériaux avec des performances améliorées.The demand for miniaturized mobile wireless systems have increased the need to integrate electrically small antennas which are generally characterized by poor performances and low efficiency. Methods such as the use of dielectric, slots, parasitic components, … have been applied over the years to enhance the performance of such antennas. However they are empirical and based on time-consuming optimisations. Other methods like antenna current optimization based on modal analysis are systematic methods which have been proposed. It has also been shown that the use of artificial materials known as metamaterial inclusions as parasitic element help to improve antenna performance at lower cost. The choice of the right inclusion for an antenna design is complicated especially when the antenna is non-canonical and arbitrary.In this thesis, we propose a systematic method for enhancing the performance of antenna using metamaterial inclusion as a parasitic element. The method is used for designing parasitic metamaterial antenna with the potential to analyse both the radiation and scattering properties of the parasitic metamaterial design. It uses the characteristic modal method to evaluate the quantitative stored energy of metamaterial inclusions which provide quantitative information on the near-field behaviour of the inclusion. The modal stored energy method is compared to the effective parameter method for describing inclusions and they both show good qualitative agreement. In the parasitic metamaterial antenna design process, characteristic mode is applied to get an insight into the radiation properties of the structure and an inclusion is chosen to compensate the stored energy of the antenna element based on the quantity of its modal stored energy. The coupling between the antenna and the inclusion is analysed using the inter-modal coupling co-efficient. It represents the scattering between the antenna and the inclusion and defines how the positioning and separation distance between the two elements affect the overall performance of the metamaterial-inspired system. The proposed methodology is validated with a prototype that show a good agreement between the simulated and measured result. The method is further applied in investigating the enhancement of integrated antenna using electromagnetic cloaking. The cloak couples to the passive element in its vicinity and allow the active antenna element to operate with a better radiation efficiency. The proposed method show usefulness for future design of parasitic metamaterial systems with enhanced performance
Electromagnetic energy harvesting systems in the railway environment: State of the art and proposal of a novel metamaterial energy harvester
No full text13th European Conference on Antennas and Propagation (EuCAP), Cracovie, POLOGNE, 31-/03/2019 - 05/04/2019In this paper, an overview on energy harvesting systems in the railway environment and recent advancements is presented. Energy harvesting systems in the railway environment vary from piezoelectric energy harvesters to electromagnetic energy harvesting systems (mostly mechanical vibrations to electric energy) which has been an interesting topic for researchers specially for applications to supply power to wireless sensor networks to insure safety on the railway track. Recently, experimental measurements have been observed for electromagnetic fields in the railway environment at a wideband range of frequency from 10 kHz to 1 GHz where unintentional signals or ambient energy has shown to exist in the railway infrastructure. The design of a high efficient and compact energy harvesting system has been considered. It is based on a metamaterial structure at a given frequency compatible for railway applications which is chosen at 350 MHz. The metamaterial design has shown good absorption at 350 MHz equal to 98% with a subwavelegth structure of ?/14 and thickness ?/100. Unlike metamaterial absorbers, the energy is dissipated through a via where 84% of the energy was delivered through a resistive load of 8.5 K?
Metamaterials for non-radiative microwave functions and antennas, in Metamaterials and wave control
No full textInternational audienceCurrent and future wireless communications systems have to be smart while proposing an acceptable quality of service for given applications and optimized resource management in terms of energy consumption and spectral occupation. Moreover, the demand for nomadic devices is growing, thus requiring light, low profile and miniaturized microwave components which can easily integrate into complex systems. All these requirements can be contradictory for the conventional microwave engineer since for instance, miniaturization is usually achieved with a non-negligible impact on overall performances. Since metamaterials can be tailored to present required electromagnetic properties, it should definitely provide a higher degree of freedom in the design of both radiative and non-radiative components for wireless systems. The potential of metamaterial to improve the performances of microwave devices should also be considered. This chapter is divided in two main parts: the first one deals with metamaterial applications for non-radiative microwave components and the second one describes the potential and applications of metamaterials to microwave antennas
Enhancement of backscattering cross section from an equivalent human cylinder under oblique incidence
No full textInternational audienceAn analysis about the enhancement of backscattering radar cross section from an equivalent human body cylinder using a specific type of coating is presented. The types of coatings considered for the human body are taken to inductive meta surface (MS), inductive MS followed by a dielectric layer and an epsilon negative (ENG) metamaterial. An eigenfunction expansion method has been used to derive analytical expressions for the scattered electric and magnetic fields. It is investigated that inductive MS and inductive MS followed by a dielectric layer type of coatings cannot be used to enhance the backscattering radar cross section from the human body. It is found that an ENG metamaterial coating having specific permittivity and coating thickness can be used to significantly enhance the back-scattering radar cross section from the human body under oblique incidence. Therefore, an ENG metamaterial coating is selected for the proposed model and finally, the modelling of the proposed design is suggested
- …
