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Letteratura scientifica selezionata sul tema "METAMATERIAL REFLECTOR"

Autore: Grafiati

Pubblicato: 11 settembre 2023

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Articoli di riviste sul tema "METAMATERIAL REFLECTOR"

Huang, Wei, Ningye He, Renxia Ning e Zhenhai Chen. "Wideband Reflector and Analogue Electromagnetically Induced Reflection in Metamaterials". Crystals 11, n. 8 (19 agosto 2021): 985. http://dx.doi.org/10.3390/cryst11080985.

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Metamaterials are highly demanded for advanced applications in absorbers, sensors, and filters. However, metamaterial reflectors, especially broadband reflectors, remain challenging. In this paper, we theoretically investigate a wideband metamaterial reflector which consists of cross shaped graphene strips and a silica (SiO2) substrate. The cross shaped graphene strips are coated on the top of the structure, and the cross shape rotated 45° graphene strips are spun on the bottom of it. The calculated reflection can be tuned through length and width of the graphene strips. By comparison, not only broadband reflection but also analogue electromagnetically induced reflection (EIR) can be realized. Moreover, the structure can generate a bi-directional broadband reflection of insensitive polarization. This kind of bi-directional reflector at microwave frequencies is obtained because the top and bottom graphene strip structures are similar. We employ the electric field distribution of the designed structure to elucidate the mechanism of the analogue EIR effect. We further discuss the influence of incident angle on the analogue EIR effect. Such a bi-directional reflector can be potentially applied to a wideband reflector, antenna, and sensor.

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Zhao, Zhen-Yu, Hai-Wen Liu, Zhi-Jiao Chen, Liang Dong, Le Chang e Meng-Ying Gao. "Dual circularly polarized Fabry-Perot antenna with metamaterial-based corner reflector for high gain and high aperture efficiency". Acta Physica Sinica 71, n. 4 (2022): 044101. http://dx.doi.org/10.7498/aps.71.20211914.

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Based on the ray-tracing model, a new method of achieving a high gain and high aperture efficiency Fabry-Perot antenna with metamaterial-based corner reflector is proposed. The proposed Fabry-Perot antenna is composed of a dual circularly polarized patch antenna feed and the metamaterial-based corner reflector. The metamaterial-based corner reflector consists of four phase correction metasurfaces and a partially reflective surface. First, theory and analysis of the Fabry-Perot antenna with metamaterial-based corner reflector are presented. Then, the performances of the dual circularly polarized antenna feed, the traditional Fabry-Perot antenna, and the Fabry-Perot antenna with metamaterial-based corner reflector are compared among each other and analyzed. Finally, the proposed Fabry-Perot antenna is fabricated and measured. The measured left-hand circular polarization (LHCP) gain and the measured right-hand circular polarization (RHCP) gain of the proposed Fabry-Perot antenna are 21.4 dBi and 21.3 dBi, respectively. Comparing with the antenna feed, the LHCP gain and RHCP gain of the proposed Fabry-Perot antenna are enhanced by 16.4 dB and 16.3 dB, respectively. Compared with the traditional Fabry-Perot antenna, the metamaterial-based corner reflector acts as both a reflection surface and a phase correction surface. It manipulates the propagation direction and phase of electromagnetic wave. The proposed Fabry-Perot antenna with high gain, high aperture efficiency and low sidelobe at 2.8 GHz paves the way for developing the solar radio telescope and conducting the observation.

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BOURAS, Khedidja, Abdelhadi LABIAD, Chaker SALEH e Mouloud BOUZOUAD. "Emulation of metamaterial waveguides". Algerian Journal of Signals and Systems 3, n. 3 (15 settembre 2018): 117–24. http://dx.doi.org/10.51485/ajss.v3i3.67.

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In this work, we are interested by emulating metamaterial microwave waveguides which behave like conventional metallic ones. We use metamaterial layers based on two types of unit cells. The first one is a connected cross type unit cell which leads to a metamaterial with a near zero refraction index (n1≈ 0). The second one is a disconnected cross type unit cell which leads to a metamaterial with a refraction index greater than unity (n2 >1). With these two type of metamaterials we can define, in the metamaterial layer, different sections each one can have a refraction index equal to n1 or n2. Using these metamaterial layers we can build a metamaterial waveguide. This latter is obtained by stacking a number of layers. The waveguide is obtained by selecting an inner section with a refraction index n2 and an outer section with a refraction index n1 close to zero which plays a similar role as a metallic reflector to form the waveguide.

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McSherry, Sean, e Andrej Lenert. "Design of a gradient epsilon-near-zero refractory metamaterial with temperature-insensitive broadband directional emission". Applied Physics Letters 121, n. 19 (7 novembre 2022): 191702. http://dx.doi.org/10.1063/5.0122535.

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Gradient epsilon-near-zero (ENZ) metamaterials offer broadband directional control over thermal emission. Implementing this approach using materials that remain stable in harsh thermo-chemical environments would allow it to be broadly deployed in thermal photonics. Our prior work showed that heterostructures of rock salt MgO and perovskite BaZr0.5Hf0.5O3 (BZHO) are stable up to 1100 °C in air, with no discernible intermixing. In this work, we design a gradient ENZ metamaterial made from three lattice-matched refractory oxides: MgO, BZHO, and NiO. The miscibility of MgO and NiO makes it possible to linearly vary the ENZ frequency of the metamaterial layers. BZHO is used as a thin, interlayer diffusion barrier. We model the emissivity of our gradient ENZ metamaterial at 25 and 1000 °C to demonstrate that the spectral bandwidth of directional emission is preserved at high temperatures despite changes in the optical properties of each material. Finally, we discuss practical fabrication challenges associated with the back reflector and offer potential solutions based on advancements in hetero-integration. Overall, this work shows a pathway toward gradient ENZ metamaterials with ultrahigh-temperature stability.

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Mustapha, M. G., M. K. A. Rahim, N. A. Murad, O. Ayop, S. Tuntrakool, M. A. Baba, A. Y. Iliyasu e Mohd Ezwan Jalil. "Polarization insensitive switchable metamaterial absorber/reflector for X-band applications". Bulletin of Electrical Engineering and Informatics 9, n. 6 (1 dicembre 2020): 2443–48. http://dx.doi.org/10.11591/eei.v9i6.2196.

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A unit cell of squared shaped polarization-insensitive switchable metamaterial absorber/reflector is presented. The structure operates at 10.20 GHz under both absorber mode and reflector mode configurations. Copper wire bridging the gaps to form a circular shape structure were used as switches for operation mode selections. The structure was designed on an FR4 substrate, and the incidental wave angles were varied from 0 to 50 degrees. The structure demonstrated almost 100% absorption at resonance, 3.314 GHz percentage bandwidth at 80% as an absorber. On the other hand, as reflector, it demonstrated almost a 90% reflection and a usable bandwidth of 3.327 GHz.

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Xu, Wangren, e Sameer Sonkusale. "Microwave diode switchable metamaterial reflector/absorber". Applied Physics Letters 103, n. 3 (15 luglio 2013): 031902. http://dx.doi.org/10.1063/1.4813750.

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Deng, Guangsheng, Tianyu Xia, Jun Yang, Longzhen Qiu e Zhiping Yin. "Tunable terahertz metamaterial with a graphene reflector". Materials Research Express 3, n. 11 (15 novembre 2016): 115801. http://dx.doi.org/10.1088/2053-1591/3/11/115801.

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Aközbek, N., M. J. Bloemer e M. Scalora. "Experimental investigation of a metamaterial omnidirectional reflector". Journal of Applied Physics 104, n. 3 (agosto 2008): 033105. http://dx.doi.org/10.1063/1.2963479.

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Lu, Taoming, Youcheng Wang, Helin Yang, Xiaojun Huang, Yanfei Zhou e Jiong Wu. "Absorbing properties of metamaterial dihedral corner reflector". Materials Research Express 7, n. 2 (24 febbraio 2020): 025802. http://dx.doi.org/10.1088/2053-1591/ab7567.

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Hedayati, M. Keshavarz, S. Fahr, C. Etrich, F. Faupel, C. Rockstuhl e M. Elbahri. "The hybrid concept for realization of an ultra-thin plasmonic metamaterial antireflection coating and plasmonic rainbow". Nanoscale 6, n. 11 (2014): 6037–45. http://dx.doi.org/10.1039/c4nr00087k.

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Più fonti

Tesi sul tema "METAMATERIAL REFLECTOR"

Ratni, Badr Eddine. "Étude et conception d’antennes à base de métasurfaces destinées aux applications spatiales et aéronautiques". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS327/document.

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Cette thèse a pour but de mettre en avant les récentes avancées dans le domaine des métasurfaces. Ces structures ont été utilisées dans le but d’améliorer les performances des antennes classiques ou de concevoir de nouveaux concepts d’antenne. Les travaux menés s’inscrivent dans le cadre d’une collaboration avec des partenaires industriels qui sont Airbus Safran Lunchers, Airbus Group Innovations et le CNES. La thèse est organisée en deux parties. La première partie est consacrée aux métasurfaces utilisées comme des surfaces partiellement réfléchissantes (SPR) pour concevoir des antennes à cavité Fabry-Perot. Un modèle analytique permettant de prédire le dépointage du faisceau d’antenne par une modulation de la phase sur la SPR a été développé. Ensuite, un nouveau concept de métasurface permettant de réaliser du dépointage de faisceau est proposé. Il consiste à appliquer un gradient de phase en faisant varier l’indice effectif le long du substrat diélectrique de la SPR. La deuxième partie de cette thèse est quant à elle consacrée à la conception d’une métasurface active permettant d’émuler plusieurs fonctions. Dans un premier temps, la métasurface est utilisée comme un réflecteur présentant une reconfigurabilité fréquentielle et angulaire. Ensuite cette métasurface est utilisée comme polariseur reconfigurable où une polarisation linéaire de l'onde incidente est convertie en polarisation circulaire. Enfin, la dernière étude concerne l’utilisation de la métasurface active pour la réalisation d’une antenne à réflecteur cylindro-parabolique et à réflecteur dièdre reconfigurables
This thesis aims at highlighting recent advances in the field of metasurfaces. These structures have been used to improve the performances of conventional antennas or to design new antenna concepts. The work has been carried in the framework of a collaboration with industrial partners, namely Airbus Safran Launchers, Airbus Group Innovations and CNES. The manuscript is organized into two parts. The first part is devoted to metasurfaces used as partially reflecting surfaces (PRS) to design Fabry-Perot cavity antennas. In this part, an analytical model allowing to predict the beam steering angle by a phase modulation along the PRS is developed. Then, a new concept of metasurface allowing to steer the main antenna beam is proposed. It consists in applying a phase gradient by varying the effective index of the substrate that constitutes the PRS. The second part of this thesis is devoted to the design of an active metasurface that allows emulating different functionalities. First, the metasurface is utilized as a reflector with frequency and steering reconfigurability characteristics. Then, this metasurface is used as a reconfigurable polarizer where linearly polarized incident waves are converted into circularly polarized ones. Finally, the last study concerns the use of the active metasurface for the design of reconfigurablecylindro-parabolic and corner reflector antennas

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Ting, Choon Boon. "Universal Zero Specular Reflection Curves for MetaMaterials". Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/17469.

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Approved for public release; distribution is unlimited
Materials are generally classified in terms of their constitutive parameters, the complex permittivity and permeability , in the frequency domain. These parameters are used to determine the response of materials to electromagnetic (EM) radiation. Materials found in nature have positive real parts for both and . In recent years, researchers have shown that a new class of materials called metamaterials (MTMs), characterized by inclusions of various shapes and materials that are small compared to wavelength, result in an effectively homogeneous medium with the unique properties of negative real and which cause EM waves traveling through the medium to exhibit unusual characteristics. Zero specular reflection layers for four material types such as double positive (DPS), double negative (DNG), epsilon-negative (ENG) and mu-negative (MNG) materials are examined in this thesis. For each defined type of MTM, the transcendental equations are derived and solved numerically to generate curves for zero specular reflection. A MATLAB program was developed to generate universal curves for DPS, DNG, ENG, and MNG materials. The results were discussed and evaluated to determine wave behavior in each type of MTM as well as how they can be used as a matched-surface radar-absorbing material (RAM) for military application. The results were compared to published data.

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Tamayama, Yasuhiro. "No-Reflection Phenomena for Isotropic and Chiral Metamaterials". 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142178.

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Berry, Simon James. "Microwave surface waves on metasurfaces with planar discontinuities". Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/15283.

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The work presented within this thesis details the experimental investigation of the surface waves supported on metasurfaces. Particular attention has been given to the reflection of these surface waves from planar discontinuities associated with these metasurfaces. Various experimental techniques have been developed throughout this work to characterise surface wave supporting metasurfaces. These include a new technique for measuring the dispersion of surface waves supported on metasurfaces, characterisation of the near-field associated with the surface waves, a device for launching planar phase front surface waves and finally a technique for measuring the surface wave reflection coefficient. The dispersion of surface waves on a square array of square cross-section metal pillars has been fully characterised and compared to FEM modelling. The results show that a family of surface waves may be supported by pillar or crossed slit structures rather than just holes even though there is now no lowest cut-off frequency. A family of TM surface modes have been shown to exist with dispersions which asymptote to frequencies defined by the pillar heights (slit depth) and the refractive index of the material filling the slits. Primarily this work focussed on the surface wave properties associated with a square array of square metal patches on a dielectric coated ground plane and a Sievenpiper `mushroom' metasurface. The amplitude reflection coefficient of these surface waves has been studied for three distinct systems: Firstly for surface waves incident upon the termination of a these metasurfaces to free space, secondly for surface waves incident upon the interface between a dielectric coated and uncoated metasurface and thirdly for surface waves incident on the boundary between two metaurfaces. The reflection coefficient of surface waves incident upon the termination of the metasurface to free space is found to increase significantly with the confinement of the surface mode. This confinement, and therefore the form of the reflection coefficient, is significantly different for the two metasurfaces considered due to their dispersions. This increase in the reflection coefficient is caused by both the momentum mismatch of the surface wave compared to the freely propagating modes and the different field distributions of the two modes. The reflection coefficient of surface waves incident upon the boundary between a coated and uncoated metasurface has been experimentally characterised for the metal patch array and Sievenpiper `mushroom' metasurfaces. It is shown that the addition of a thin, significantly subwavelength, dielectric overlayer onto the metasurface vastly perturbs the surface wave dispersion. The reflection coefficient of the surface waves is found to depend on the dispersion of the mode supported on the coated and uncoated metasurface and the overlayer thickness. Most noticeably the thickness of the overlayer, by comparison to the surface wave decay length, has a significant effect on scattering to free space associated with the surface wave reflection. The final system considered was designed to investigate the impedance approximation, often used to describe metasurfaces, and found it to be an incomplete description of the surface waves supported on the metasurfaces used within this study. In the impedance approximation the two surfaces considered are said to be `impedance matched` at certain frequencies. It is demonstrated that the failure of the impedance approximation to accurately describe this system is due to the behaviour of the electric field within the metasurfaces. These are not analytically described in the impedance approximation and are required for an accurate description of the surface waves supported on these metasurfaces.

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Culhaoglu, Ali Eren [Verfasser], Peter [Akademischer Betreuer] Russer, Wolfgang J. R. [Akademischer Betreuer] Hoefer e Hans-Joachim [Akademischer Betreuer] Bungartz. "Microwave Metamaterials: Superlensing and Design of Low Reflection Coatings / Ali Eren Culhaoglu. Gutachter: Peter Russer ; Wolfgang J. R. Hoefer ; Hans-Joachim Bungartz. Betreuer: Peter Russer". München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/1031512691/34.

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Culhaoglu, Ali Eren [Verfasser], Peter Akademischer Betreuer] Russer, Wolfgang J. R. [Akademischer Betreuer] Hoefer e Hans-Joachim [Akademischer Betreuer] [Bungartz. "Microwave Metamaterials: Superlensing and Design of Low Reflection Coatings / Ali Eren Culhaoglu. Gutachter: Peter Russer ; Wolfgang J. R. Hoefer ; Hans-Joachim Bungartz. Betreuer: Peter Russer". München : Universitätsbibliothek der TU München, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20120724-1092907-0-5.

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Kadlec, Radim. "Analýza elektromagnetické vlny na rozhraní heterogenního prostředí". Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-233658.

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The proposed dissertation thesis contains an analysis of conditions on the boundary between layers having varied electromagnetic properties. The research is performed using consistent theoretical derivation of analytical formulas, and the underlying problem is considered also in view of multiple boundaries including the effect of the propagation of electromagnetic waves having different instantaneous speed. The author presents a survey and formulation of the basic characteristics of methods used for electromagnetic wave propagation analysis; in this respect, special emphasis is placed on radial models. The processing of the topic involved the designing and verification (using a set of different, layered planar materials) of algorithms to analyze the electromagnetic field components. The algorithm was assembled to enable simple evaluation of all components of the electromagnetic field in relation to the speed of the wave propagation in a heterogeneous environment. The proposed algorithms are compared by means of different numerical methods for the modelling of electromagnetic waves on the boundary between materials; moreover, electromagnetic field components in common points of the model were also subject to comparison. When in conjunction with tools facilitating the analysis of material response to the source of a continuous signal, the algorithms constitute a supplementary instrument for the design of a layered material. Such design enables the realization of, for example, recoilless plane, recoilless transition between different types of environment, and filters for both optical and radio frequencies.

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El, Ayouch Aliyasin. "Opacité et transparence générées par les résonances locales dans les métamatériaux Acoustiques". Thesis, Besançon, 2015. http://www.theses.fr/2015BESA2007.

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Le domaine des métamatériaux acoustiques connaît un succès grandissant depuis maintenant une vingtaine d’années, notamment en raison de phénomènes exotiques aux perspectives d’applications plus que prometteuses : « l’invisibilité » acoustique en est l’exemple le plus manifeste. Dans cette thèse, nous présentons des métamatériaux acoustiques à résonances locales, et qui permettent de générer aussi bien de l’opacité que de la transparence acoustique. C’est plus particulièrement le couplage entre résonateurs de différentes formes qui est l’objet de nos investigations. Notre étude nous a permis de comprendre que la diffraction est l’une des principales limitation à l’omnidirectionalité des performances d’opacité, que nous avons caractérisé au moyen d’un banc ultrasonore motorisé. Un tel phénomène de diffraction est dû à la présence d’un réseau, et nous proposons dans notre étude des solutions qui permettent de dépasser cette limitation. A partir de cette étude, nous avons ainsi pu transposer au domaine sonore les résultats obtenus pour les ultrasons, ce qui nous a permis de réaliser deux principaux types de dispositifs : des métamatériaux acoustiques aux fonctions de réflecteur d’une part et d’absorbant basses fréquences d’autre part. Enfin, l’étude en homogénéisation de ce type de structure a aussi révélé un effet de densité effective quasi-nulle, dont les applications vont du contrôle de front d’onde, à la furtivité acoustique. De tels résultats offrent un potentiel d’application dans de nombreux champs, que ce soit pour le bâtiment ,l’automobile, l’aéronautique, ou l’acoustique sous-marine
For more than twenty years now, Acoustic Metamaterials are experiencing a growing success, partlydue to exotic phenomena and their wide variety of extremely promising applications: “InvisibilityCloak” is the most vivid example of this. In this thesis, we report on designs of locally resonantacoustic metamaterials, that enable us to generate both sound opacity and transparency. It is moreparticularly coupling between resonators having different forms which is the focus of our work.This study permit us to understand that diffraction is one of the main limitation of omnidirectionalcapabilities involving locally resonant perforated plates, as supported by experimental investigationsrealized using a motorized ultrasonic set-up. We proposed solutions to overcome such a limitation,in the case where the opacity mechanism uses diffraction gratings. From this, we transposed theresults obtained in ultrasonic frequencies to the audible range, which permits us to develop twomain kinds of acoustic devices based on metamaterials: broadband reflectors and low-frequencyabsorbers. Finally, homogenization study of such structures revealed an effect of density near-zero,with applications from shaping wave front, to acoustic furtiveness. Such results paves the way forpromising applications in various field, including construction, automotive and aeronautical industries,submarine acoustics and so on

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Hammoud, Mohamad. "Etude et conception d'antennes imprimées sectorielles à faibles lobes arrière pour réseau Wi-Fi outdoor maillé". Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTS032.

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Dans le cadre du réseau maillé Wi-Fi sur la bande 2,4 GHz en environnement outdoor, nous concevons des antennes sectorielles à très faible rapport de rayonnement avant – arrière. Ceci permet de limiter les interférences co-canales. Nous étudions tout d'abord des éléments rayonnants associés à un plan réflecteur en métamatériau. Ce dernier est basé sur une structure de Sievenpiper dite structure « champignon ». Cette structure est constituée de motifs périodiques imprimés sur un substrat. A l’aide de simulations des diagrammes de dispersion, et de la phase du coefficient de réflexion sur ces structures, avec de nombreux résultats issus de la littérature, nous caractérisons ces plans réflecteurs. Nous sommes alors en mesure de proposer des critères sur la géométrie des motifs pour que le comportement haute impédance de la structure coïncide avec la bande électromagnétique interdite. Le comportement des antennes, élément rayonnant et réflecteur, présente des performances de rayonnement et de bandes passantes très intéressantes. Pour des raisons budgétaires cette structure n'est pas retenue. Une partie de cette thèse explore alors l'effet de la géométrie des éléments rayonnants imprimés associés aux réflecteurs sur les performances en gain et sur le rapport avant/arrière. Le choix se porte sur une géométrie de type boucle. Ce travail est mené tant grâce à des simulations électromagnétiques 3D ainsi qu'à des expérimentations. Des mesures sur terrain d'un prototype d'un système constitué de trois antennes tri-sectorielles munis d'un radôme valide et clôt l'étude
In the frame of outdoor meshed Wi-Fi network operating in the 2.4 GHz frequency band, we conceive sectoral antennas with very low front to back radiation ratio. This should limit co-channel interferences between neighboring base stations. We first study radiating elements in microstrip technology associated with a reflector based on metamaterials. The latter is based on the structure of Sievenpiper, the so-called "mushroom" structure. This structure comprises periodic pattern sprinted on a substrate. Simulations of the dispersion diagram and of the phase of the reflection coefficient, linked to numerous results from the literature, allow us to perform a full-through characterization of these reflectors. We can therefore propose a criterion on the geometry of the patterns bringing the high-impedance frequency band within the forbidden electromagnetic bandgap. The behavior of the overall antenna, radiant element and reflector, exhibits very interesting performances considering bandwidth and radiation lobes. For economic reasons, this structure is not retained and we switch to a simple perfect electric conductor plane. A part of this thesis explores the impact of printed antenna geometry and its associated reflector on the gain and front to back ratio characteristics. We finally choose a loop geometry. This work is achieved with 3D electromagnetic simulations and with outdoor measurements. On-field experiments on a prototype comprising 3 tri-sectoral antennas assembled under a Radome validate and concludes the study

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Aivaliotis, Alexios. "Propagation et diffusion des ondes au niveau macroscopique des métamatériaux limites via le modèle micromorphique relaxé". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI073.

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Les métamatériaux mécaniques microstructurés attirent de plus en plus l'attention de la communauté scientifique et technique. Nous choisissons une approche qui évoque la théorie classique de l'élasticité : celle de la mécanique des milieux continus enrichie. Le but de cette thèse est d'utiliser le nouveau modèle de continuité enrichie appelé modèle micromorphique relaxé détendu afin d'étudier la propagation des ondes et les phénomènes de diffusion aux interfaces entre matériaux et métamatériaux. Lorsqu'il s'agît d'étudier les propriétés de diffusion de structures de taille finie, il devient difficile de traiter les conditions limites correctes. Nous montrons comment les problèmes aux valeurs limites de domaines finis peuvent être mis en place dans le cadre du modèle micromorphique relaxé. Nous mettons en place la solution d'onde plane complète de la diffusion à partir d'une interface séparant un milieu de Cauchy d'un milieu micromorphique relaxé. Les conditions aux limites macroscopiques généralisées sont présentées. Ils permettent de bien décrire les propriétés de diffusion. Le flux d'énergie généralisé associé est introduit. On considère deux cas différents dans lesquels le milieu homogène gauche est soit plus rigide soit plus flexible que le métamatériau droit et le coefficient de transmission est obtenu en fonction de la fréquence et de la direction de propagation. Le contraste des raideurs macroscopiques des deux milieux, influencent l'apparition des ondes Stoneley. On considère par la suite un problème de propagation des ondes de volume et on démontre que les formes d'ondes transitoires résultant de plusieurs impulsions localisées dans un matériau microstructuré peuvent être reproduite. Nous comparons la réponse dynamique d'un matériau microstructuré et lié à celle d'un milieu lié avec des propriétés cinématiques particulières. On démontre que, bien que la théorie de Cauchy soit capable de décrire le comportement global de la métastructure à de basses fréquences, le modèle micromorphique détendu va bien au-delà en donnant une description correcte de la propagation de l'impulsion dans la bande de fréquence et à des fréquences qui croisent les branches optiques. Enfin, on présente le cas d'une dalle de métamatériau de largeur finie. Ses propriétés de diffusion sont étudiées en utilisant une solution semi-analytique du modèle micromorphique relaxé et comparées à des simulations. Le coefficient de réflexion obtenu par les deux méthodes est présenté en fonction de la fréquence et la direction de propagation de l'onde incidente. On trouve un excellent accord pour une large gamme de fréquences, allant de la limite des ondes longues aux fréquences au-delà de la première limite de la bande, et pour des angles d'incidence allant d'une incidence normale à une incidence presque parallèle. Le cas d’un métamatériau semi-infinie est également présenté et est considéré comme une mesure fiable du comportement moyen de la métastructure finie
Mechanical microstructured metamaterials are increasingly gaining attention from the scientific and engineering community. The question of modeling the behavior of metamaterials is of extreme importance. Some choose an approach, which is reminiscent of the classical theory of elasticity: enriched continuum mechanics. We employ the enriched continuum model named relaxed micromorphic model in order to study wave propagation and scattering at interfaces between materials and metamaterials. Dealing with the correct boundary conditions at the macroscopic scale becomes challenging. We show how finite-domain boundary value problems can be set-up in the framework of the relaxed micromorphic model. We set up the full plane wave solution of the scattering from an interface separating a Cauchy medium from a relaxed micromorphic one. Both media are isotropic and semi-infinite. Generalized macroscopic boundary conditions are presented, which allow the effective description of the scattering properties of an interface between a homogeneous solid and a mechanical metamaterial. The associated generalized energy flux is introduced. We show that the contrast of the macroscopic stiffnesses of the two media, together with the type of boundary conditions strongly influence the onset of Stoneley waves at the interface. This allows to tailor the scattering properties of the interface at both low and high frequencies, ranging from zones of complete transmission to zones of zero transmission well beyond the band-gap. We then consider a bulk wave propagation problem and show that the transient waveforms arising from several localised pulses in a micro-structured material can be reproduced. We compare the dynamic response of a bounded micro-structured material to that of bounded continua with special kinematic properties. We show that, while the Cauchy theory is able to describe the overall behavior of the metastructure only at low frequencies, the relaxed micromorphic model goes far beyond by giving a correct description of the pulse propagation in the frequency bandgap and at frequencies intersecting the optical branches. Finally, we present the case of a metamaterial slab of finite width. Its scattering properties are studied via a semi-analytical solution of the relaxed micromorphic model and compared to numerical simulations encoding all details of the selected microstructure. The reflection coefficient obtained via the two methods is presented as a function of the frequency and the direction of propagation of the incident wave. We find excellent agreement for a large range of frequencies. The case of a semi-infinite metamaterial is also presented and is seen to be a reliable measure of the average behavior of the finite metastructure

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Libri sul tema "METAMATERIAL REFLECTOR"

Ozbay, E., G. Ozkan e K. Aydin. Left-handed metamaterials—A review. A cura di A. V. Narlikar e Y. Y. Fu. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199533046.013.20.

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This article focuses on left-handed metamaterials (LHMs). It begins with a discussion of negative-permeability metamaterials, with particular emphasis on split-ring resonators (SRRs) and SRRr arrays and how magnetic permeability influences the response of materials to the incident magnetic field. It then considers the transmission spectra of SRR, LHM and a composite metamaterial as well as the reflection characteristics of a one-dimensional double-negative material. It also examines the effect of disorder on the transmission and reflection properties of ordered left-handed materials, along with the negative refraction, negative phase velocity, and subwavelength imaging and resolution of LHMs. The article concludes with an analysis of planar negative-index metamaterials.

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Werner, Douglas H., Sawyer D. Campbell e Lei Kang. Nanoantennas and Plasmonics: Modelling, Design and Fabrication. Institution of Engineering & Technology, 2020.

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Capitoli di libri sul tema "METAMATERIAL REFLECTOR"

Kumar, Amit, Binod Kumar Kanaujia e Abdul Quaiyum Ansari. "Wideband MM FSS Reflector for CP Millimeter-Wave Antennas". In Metamaterials Science and Technology, 1–20. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-15-8597-5_17-1.

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Kumar, Amit, Binod Kumar Kanaujia e Abdul Quaiyum Ansari. "Wideband MM FSS Reflector for CP Millimeter-Wave Antennas". In Metamaterials Science and Technology, 475–94. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-6441-0_17.

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Singh, Amit K., Mahesh P. Abegaonkar e Shiban Kishen Koul. "High-Gain Antennas Using a Reflection-Type Metasurface". In Metamaterials for Antenna Applications, 77–96. Boca Raton: CRC Press, 2021. http://dx.doi.org/10.1201/9781003045885-4.

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Semchenko, I. V., e S. A. Khakhomov. "The Competition of Bragg Reflection and Fresnel’S Reflection of Electromagnetic Waves in the Artificial Helicoidal Bianisotropic Media with Local Chirality". In Advances in Electromagnetics of Complex Media and Metamaterials, 307–18. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-007-1067-2_19.

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Borzdov, A. N. "Transmission and Reflection of Electromagnetic Waves by the Plane Stratified Structures Possessing Gyrotropic Properties". In Advances in Electromagnetics of Complex Media and Metamaterials, 259–69. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-007-1067-2_15.

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Semchenko, I. V., e V. E. Kaganovich. "Selective Reflection at an Oblique Incidence of Electromagnetic Waves onto Stratified Periodic Gyrotropic Structures". In Advances in Electromagnetics of Complex Media and Metamaterials, 271–80. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-007-1067-2_16.

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Mujawar, Mehaboob, e Subuh Pramono. "Metamaterial-Based Absorber". In Advances in Wireless Technologies and Telecommunication, 110–20. IGI Global, 2023. http://dx.doi.org/10.4018/978-1-6684-8287-2.ch005.

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In this chapter, the authors discuss metamaterial absorbers. The need for active absorbers and also different types of active absorbers have been listed in detail such as switchable absorber/reflector, switchable absorber, and tunable absorbers. The recent trends and the work investigated by researchers around the globe have also been mentioned in brief, which can set a benchmark for further research in the field of metamaterial absorbers. The proposed MTM structure is made up of four-square patches. The structure was designed on an FR4 substrate measuring 11 mm by 11 mm with a thickness of 1.60 mm. Other properties of the substrate include relative permittivity of 4.4 and loss tangent of 0.019. The structure has a full ground plane to minimize transmission. The structure's primary resonance for absorber mode configuration is at 8 GHz. The simulations of the proposed structure were carried out using CST.

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"Inverted-F Antenna Above an Electromagnetic Band-Gap Reflector". In Low-Profile Natural and Metamaterial Antennas, 133–42. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781118859704.ch11.

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Kumar, Asish, Khem B. Thapa, Narendra Kumar e Anil K. Yadav. "Tunable Broadband Reflector Using a One-Dimensional Photonic Crystal Containing Metamaterial with Symmetrically Introduced Magnetized Cold Plasma Defect". In Advances in Photonic Crystals and Devices, 143–59. CRC Press, 2019. http://dx.doi.org/10.1201/9781351029421-9.

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Kruk, Sergey, e Yuri Kivshar. "Tailoring transmission and reflection with metasurfaces". In Dielectric Metamaterials, 145–74. Elsevier, 2020. http://dx.doi.org/10.1016/b978-0-08-102403-4.00010-4.

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Atti di convegni sul tema "METAMATERIAL REFLECTOR"

Yoo, Min-Yeong, e Sungjoon Lim. "Switchable electromagnetic metamaterial reflector/absorber". In 2012 Asia Pacific Microwave Conference (APMC). IEEE, 2012. http://dx.doi.org/10.1109/apmc.2012.6421626.

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Shankhwar, Nishant, Ritika Ranga, Yogita Kalra e Ravindra K. Sinha. "Dielectric ring based metamaterial perfect reflector". In Metamaterials, Metadevices, and Metasystems 2019, a cura di Nader Engheta, Mikhail A. Noginov e Nikolay I. Zheludev. SPIE, 2019. http://dx.doi.org/10.1117/12.2529033.

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Obermeier, Richard, e Jose Angel Martinez-Lorenzo. "Metamaterial-based compressive reflector antenna optimization". In 2017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. IEEE, 2017. http://dx.doi.org/10.1109/apusncursinrsm.2017.8072213.

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Ghosh, Saptarshi, Daecheon Lim e Sungjoon Lim. "Absorber/Reflector Switchable Metamaterial with Polarization-Selectivity". In 2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. IEEE, 2018. http://dx.doi.org/10.1109/apusncursinrsm.2018.8608840.

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Singh, Baljit, Yogita Kalra e Kamal Kishor. "Dielectric Metamaterial based Broadband Reflector in Visible spectrum". In Frontiers in Optics. Washington, D.C.: OSA, 2019. http://dx.doi.org/10.1364/fio.2019.jtu4a.73.

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Zhao, Rui, Linda Shao e Weiren Zhu. "Switchable metamaterial absorber and reflector using PIN diodes". In 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT). IEEE, 2019. http://dx.doi.org/10.1109/icmmt45702.2019.8992912.

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Wen, Yong-diao, Shaobin Liu, Haifeng Zhang, Xue Feng e Ling-Ling Wang. "A tunable microwave metamaterial absorber/cross-polarization reflector". In 2017 Progress In Electromagnetics Research Symposium - Spring (PIERS). IEEE, 2017. http://dx.doi.org/10.1109/piers.2017.8262189.

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Zhong, Hongtao, Jifei Zou, Li Ye, Pu Tang e Jing Tian. "A Metamaterial-based Absorptive Reflector Improved Angular Stability". In 2022 IEEE 10th Asia-Pacific Conference on Antennas and Propagation (APCAP). IEEE, 2022. http://dx.doi.org/10.1109/apcap56600.2022.10069613.

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Yan, Min, e Niels Asger Mortensen. "Metamaterial Reflector for Hollow-Core Infrared Fiber Design". In Quantum Electronics and Laser Science Conference. Washington, D.C.: OSA, 2010. http://dx.doi.org/10.1364/qels.2010.jwa5.

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Morgan, Zachary C. P. O., Kenneth L. Morgan, Jeremy A. Bossard, Cooper S. Cicero, Micah D. Gregory, Pingjuan L. Werner, Douglas H. Werner, Scott F. Griffiths e Matthew L. Ketner. "Design techniques for loss mitigation in metamaterial reflector antennas". In 2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. IEEE, 2015. http://dx.doi.org/10.1109/aps.2015.7304981.

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