Showing papers by "Shah Nawaz Burokur published in 2013"

High Beam Steering in Fabry–Pérot Leaky-Wave Antennas

Abstract: A high-gain low-profile Fabry-Perot (FP) leaky-wave antenna (LWA) presenting one-dimensional high beam steering properties is proposed in this letter. The structure consists of a ground plane and a varying inductive partially reflective surface (PRS). A microstrip patch antenna is embedded into the cavity to act as the primary feed. As design examples, antennas are designed to operate at 9.5 GHz. Subwavelength FP cavities with fixed overall thickness of λ0 /6 (where λ0 is the free-space operating wavelength) are fabricated and measured. The impact of varying the PRS inductance is analyzed. It is shown that a high beam steering angle from broadside toward endfire direction close to 60 can be obtained when judiciously designing the inductive grid of the PRS.

Low-Profile Substrate-Integrated Lens Antenna Using Metamaterials

Abstract: A low-profile substrate-integrated lens antenna is designed using planar metamaterials for a broadband operation. The lens antenna is based on embedding a Vivaldi antenna source inside a parallel-plate waveguide to illuminate a half Maxwell fish-eye (HMFE) lens operating in X-band. The focusing condition of the lens, requiring a gradient refractive index is achieved through the use of complementary nonresonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher inserted into the parallel-plate waveguide. The electric field distribution inside the antenna system has also been explored numerically. Far-field radiation patterns have been measured on a fabricated prototype in an anechoic chamber. It has been shown from both near- and far-field plots that the proposed planar antenna presents good focusing properties.

Experimental verification of isotropic radiation from a coherent dipole source via electric-field-driven LC resonator metamaterials.

Abstract: It has long been conjectured that isotropic radiation by a simple coherent source is impossible due to changes in polarization. Though hypothetical, the isotropic source is usually taken as the reference for determining a radiator's gain and directivity. Here, we demonstrate both theoretically and experimentally that an isotropic radiator can be made of a simple and finite source surrounded by electric-field-driven LC resonator metamaterials designed by space manipulation. As a proof-of-concept demonstration, we show the first isotropic source with omnidirectional radiation from a dipole source (applicable to all distributed sources), which can open up several possibilities in axion electrodynamics, optical illusion, novel transformation-optic devices, wireless communication, and antenna engineering. Owing to the electric- field-driven LC resonator realization scheme, this principle can be readily applied to higher frequency regimes where magnetism is usually not present.

Phase-compensated metasurface for a conformal microwave antenna

Abstract: The in-phase radiation from a conformal metamaterial surface is numerically and experimentally reported. The LC-resonant metasurface is composed of a simultaneously capacitive and an inductive grid constituted by copper strips printed on both sides of a dielectric board. The metasurface is designed to fit a curved surface by modifying its local phase. The latter phase-compensated metasurface is used as a reflector in a conformal Fabry-Perot resonant cavity designed to operate at microwave frequencies. Far-field measurements performed on a fabricated prototype allow showing the good performances of such a phase-compensated metasurface in restoring in-phase emissions from the conformal surface and producing a directive emission in the desired direction.

Metamaterial-based half Maxwell fish-eye lens for broadband directive emissions

Abstract: The broadband directive emission from a metamaterial surface is numerically and experimentally reported. The metasurface, composed of non-resonant complementary closed ring structures, is designed to obey the refractive index of a half Maxwell fish-eye lens. A planar microstrip Vivaldi antenna is used as transverse magnetic polarized wave launcher for the lens. A prototype of the lens associated with its feed structure has been fabricated using standard lithography techniques. To experimentally demonstrate the broadband focusing properties and directive emissions, both the far-field radiation patterns and the near-field distributions have been measured. Measurements agree quantitatively and qualitatively with theoretical simulations.

Inductive-varying grid for highly beam-steerable cavity antennas

Abstract: The design of a locally one-dimensional inductive-varying metamaterial operating near 10 GHz is reported. This is combined with a fixed capacitive grid to design a phase-varying metasurface. This composite metasurface is then used as a partially reflecting surface (PRS) together with a perfect electric conductor surface to form a resonant Fabry-Perot type cavity. A patch antenna acting as a primary source is embedded in the cavity to constitute a highly beam-steerable directive antenna. A 56° deflection of the antenna beam is experimentally observed.

Excitation of trapped modes from a metasurface composed of only Z-shaped meta-atoms

Abstract: A printed planar Z-shaped meta-atom has recently been proposed as an alternative design to the conventional electric-LC resonator for achieving negative permittivity. Transforming the LC topology of the resonator helps to facilitate transposition of geometrical parameters for the optical regime and also to improve the metamaterial homogeneity. In this work, we discuss about the excitation of a dark or trapped mode in such Z-shaped meta-atom. The electromagnetic behavior of the meta-atom has been investigated through both simulations and experiments in the microwave regime. Our results show that the Z meta-atom exhibits a trapped mode resonance. Depending on the orientation of the polarized electromagnetic field with respect to the Z atom topology and the incident plane, the excitation of the dark mode can lead either to a narrowband resonance in reflection or to a very asymmetric Fano-like resonance in transmission, analog of electromagnetically induced transparency. Compared to other structures, the Z me...

Reducing physical appearance of electromagnetic sources

Abstract: We propose to use the concept of transformation optics for the design of novel radiating devices. By applying transformations that compress space, and then that match it to the surrounding environment, we show how the electromagnetic appearance of radiating elements can be tailored at will. Our efficient approach allows one to realize a large aperture emission from a small aperture one. We describe transformation of the metric space and the calculation of the material parameters. Full wave simulations are performed to validate the proposed approach on different space compression shapes, factors and impedance matching. The idea paves the way to interesting applications in various domains in microwave and optical regimes, but also in acoustics.

Thin Conformal Directive Fabry–Pérot Cavity Antenna

Abstract: A compensated-phase partially reflective surface (PRS) is proposed in this letter. It is used together with a metallic ground plane to form a low-profile Fabry-Perot (FP) cavity antenna conformed on a cylindrical surface. A microstrip patch antenna is embedded inside the cavity to act as the primary feed. To validate the proposed PRS, an antenna is designed to operate at the 5.7-GHz Wi-Fi frequency. The subwavelength FP cavity with a fixed overall thickness of λ0/10 (where λ0 is the free-space operating wavelength) is fabricated and measured. The impact of compensating the PRS phase is analyzed.

Active metasurface for low-profile reconfigurable antennas

Abstract: The analysis and design of a low-profile Fabry-Perot (FP) cavity antenna comprising an active metasurface are presented. The antenna under investigation is formed by embedding a feeding source in a cavity composed of a Perfect Electrical Conductor (PEC) surface and a metasurface reflector. Several configurations of such antennas are presented to achieve different desired performances such as high directivity, frequency agility and beam steering.

Broadband metamaterial-based half Maxwell fish-eye lens antenna

Abstract: A low-profile substrate-integrated lens antenna is designed using planar metamaterials for a broadband operation. The lens antenna is based on embedding a Vivaldi source inside a parallel-plate waveguide to illuminate a half Maxwell fish-eye (HMFE) lens operating in X-band. The focusing condition of the lens, requiring a gradient refractive index is achieved through the use of complementary non-resonant metamaterial structures. Far-field radiation patterns have been measured on a fabricated prototype in an anechoic chamber. It has been shown that the proposed planar antenna presents good focusing properties.

X-band metamaterial-based Luneburg lens antenna

Abstract: A metamaterial-based low profile antenna is presented in the 8-12 GHz frequency range (X-band). The antenna is designed in a parallel-plate TEM waveguide configuration. A planar metamaterial-based Luneburg lens and a Vivaldi antenna that illuminates the latter lens are embedded inside the TEM waveguide. The focusing condition of the lens, requiring a gradient refractive index is achieved through the use of complementary non-resonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher. A prototype has been fabricated using standard printed circuit board techniques and has been measured in an anechoic chamber. A good qualitative agreement is observed between simulations and experiments. The proposed planar antenna presents good focusing properties over the X-band frequency range.

Broadband low profile substrate-integrated antenna based on gradient index lens

Abstract: A broadband metamaterial-based low profile antenna is presented in the 8-12 GHz frequency band. The antenna is composed of a parallel-plate TEM waveguide embedding a planar gradient index Luneburg lens and a slot Vivaldi antenna that illuminates the latter lens. The focusing condition of the lens, requiring a gradient refractive index is achieved through the use of complementary non-resonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher. A prototype fabricated using standard printed circuit board techniques has been measured in an anechoic chamber. A good qualitative agreement is observed between simulations and experiments. The proposed planar antenna presents good focusing properties.

Interpretation of the electric resonance in Z-shaped meta-atom

Abstract: A planar Z-shaped meta-atom has been recently proposed as an alternative design to the conventional electric-LC (ELC) resonator for achieving negative permittivity. Transforming the LC topology of the resonator helps to facilitate transposition of geometrical parameters for the optical regime and also to improve the metamaterial homogeneity. In this work, we discuss about the interpretation of the resonance in such Z-shaped meta-atom.

Metamaterials-based gradient index broadband lens antennas

Abstract: Gradient index lenses are proposed to transform a cylindrical wave into a plane one. The lenses are designed from metamaterials engineering in a wide frequency band. A primary source operating in the whole X-band is used to feed the lenses. The lens-antenna systems are low profile and exhibit a directive emission in the H-plane. A very good agreement is observed between measurements performed on the fabricated lens-antennas and numerical simulations.

Analysis of a subwavelength Z-shaped metamaterial

Abstract: A Z-shaped easy made planar meta-atom is presented as an alternative design to the conventional electric-LC (ELC) resonator for achieving negative permittivity. Transforming the LC topology of the resonator helps to facilitate transposition of geometrical parameters for the optical regime and also to improve the metamaterial homogeneity. Our approach aims to simplify the resonator design and achieve a lower resonance frequency without being limited by fabrication techniques. The electromagnetic behaviour is investigated through both simulations and experiments in the microwave regime. Our results show that the developed meta-atom exhibits a strong electric response to normally incident radiation and can be used very effectively in producing materials with negative permittivity. The Z-shaped structure is also shown to present a higher effective medium ratio and can possibly find various applications in planar high frequency passive circuits due to the simplicity of fabrication.

Engineering of source appearance via transformation optics concept

Abstract: The use of transformation optics concept for the design of miniaturized radiating devices is investigated. By choosing transformations that compress space, and then match it to the surrounding radiation environment, we are able to alter the physical size of the embedded source. We show that a small aperture antenna can then behave as one with a large aperture. A study of the transformation of the space metric and the material parameter calculation is presented. Simulations are performed to validate the proposed approach at microwave frequencies. This study paves the way to interesting applications in telecommunications and aeronautical domain.

Métamatériaux à gradient d’indice pour les antennes-lentilles large-bande

Abstract: REE N°4/2013 63 LES METAMATERIAUX Abdallah Dhouibi1 , Shah Nawaz Burokur2,3 , Andre de Lustrac2 3 , Alain Priou1 LEME, Universite Paris Ouest1 , IEF, Universite Paris-Sud, CNRS, UMR 8622 , Universite Paris-Ouest3 Introduction Les avancees dans les etudes des interactions onde-matiere nous permettent aujourd’hui d’envisa- ger la conception de nouveaux types de dispositifs antennaires bases sur le controle des parametres electromagnetiques des metamateriaux. De nom- breuses etudes et experiences ont ete menees ces dernieres annees [1] sur les structures a gradient d’in- dice (GRIN). L’utilisation de telles structures permet principalement de focaliser les ondes radio par l’uti- lisation de structures spheriques ou hemispheriques a saut d’indice. Des travaux recents ont ete menes sur de telles lentilles et notamment sur leurs analyses electromagnetiques pour les presenter comme des alternatives aux lentilles dielectriques convention- nelles. En effet, au lieu de controler le trajet de l’onde a l’interface entre deux dielectriques differents, on le fait par le gradient d’indice dans une structure a metamateriaux. Dans ce pap

Metamaterial-based Fabry-Pérot leaky wave antennas: low profile, high directivity, frequency agility and beam steering

Abstract: The analysis and design of subwavelength metamaterial-based Fabry-Perot (FP) leaky wave antennas (LWAs) are presented. The antennas under investigation are formed by embedding a feeding source in a cavity composed of a Perfect Electrical Conductor (PEC) surface and a metasurface reflector. Several configurations of such antennas are presented to achieve different desired performances such as: high directivity, frequency agility and beam steering.

Novel antenna concepts via coordinate transformation

Abstract: Coordinate transformation is an emerging field which offers a powerful and unprecedented ability to manipulate and control electromagnetic waves. Using this tool, we demonstrate the design of novel antenna concepts by tailoring their radiation properties. The wave manipulation is enabled through the use of engineered dispersive composite metamaterials that realize the space coordinate transformation. Three types of antennas are considered for design: a directive, a beam steerable and a quasi-isotropic one. Numerical simulations together with experimental measurements are performed in order to validate the coordinate transformation concept. Near-field cartography and far-field pattern measurements performed on a fabricated prototype agree qualitatively with Finite Element Method (FEM) simulations. It is shown that a particular radiation pattern can be tailored at ease into a desired one by modifying the electromagnetic properties of the space around radiator. This idea opens the way to novel antenna design techniques for various application domains such as the aeronautical and transport fields.

Metamaterial-based compact cylindrical base station antennas

Abstract: The study deals with the modelling, practical implementation and characterization of a directional antenna controllable through 360° in the [2 - 2.5 GHz] frequency band. The antenna is composed of a central omnidirectional broadband monopole feed surrounded by a metamaterial made of one or two controllable layers of metallic strips printed on a dielectric substrate, which can be electrically continuous or discontinuous. By controlling the distribution of reflective and transparent regions of the latter metamaterial around the central feed, a directional emission having an angular beamwidth lower or equal to 60° and controllable through 360° is produced in the UMTS and WIFI frequency bands, demonstrating the broadband operation of this antenna.

Reducing and increasing the apparent size of electromagnetic sources through transformation optics

Abstract: Transformation optics concept is used to change the physical size of radiating sources. By choosing transformations that either compress or expand space, and then match it to the surrounding radiation environment, we are able to either increase or reduce the aperture size of the embedded source. We show that a small aperture antenna can then behave as one with a large aperture and vice-versa. A study of the two transformations of the space metric is presented. Simulations are performed to validate the proposed approach at microwave frequencies. This study paves the way to interesting applications in telecommunications and aeronautical domains.

Coordinate transformation applied to change physical appearance of radiating sources

Abstract: The use of transformation optics concept to change the physical size of radiating sources is investigated. By choosing transformations that compress space, and then match it to the surrounding radiation environment, we are able to miniaturize the physical size of the embedded source. We show that a small aperture antenna can then behave as one with a large aperture. A study of the transformation of the space metric and the material parameter calculation is presented. Simulations are performed to validate the proposed approach at microwave frequencies. This study paves the way to interesting applications in telecommunications and aeronautical domain.

New trends in antenna design: transformation optics approach

Abstract: Transformation optics is an emerging field offering a powerful and unprecedented ability to manipulate and control electromagnetic waves. Using this tool, we demonstrate the design of novel antenna concepts by tailoring their radiation properties. The wave manipulation is enabled through the use of engineered dispersive composite metamaterials that realize a space coordinate transformation. Numerical simulations together with experimental measurements are performed in order to validate the coordinate transformation concept. Near-field cartography and far-field pattern measurements performed on fabricated prototypes agree qualitatively with Finite Element Method (FEM) simulations. It is shown that a particular radiation pattern can be tailored at ease into a desired one by modifying the electromagnetic properties of the space around the radiating element. This idea opens the way to novel antenna design techniques for various application domains such as aeronautical and transport fields.