Abdallah Dhouibi

High Beam Steering in Fabry–Pérot Leaky-Wave Antennas

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.

Compact Metamaterial-Based Substrate-Integrated Luneburg Lens Antenna

A compact and small electric-size aperture directive broadband Luneburg lens antenna is presented. The substrate-integrated lens antenna is based on embedding a Vivaldi antenna source inside a parallel-plate waveguide to illuminate a Luneburg 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. A prototype fabricated using standard printed circuit board techniques has been measured in an anechoic chamber. The electric field distribution inside the antenna system has also been explored using a two-dimensional near-field microwave scanning setup. A good qualitative agreement is observed between simulations and experiments. It has been shown from both far- and near-field measurements that the proposed planar antenna presents good focusing properties.

Low-Profile Substrate-Integrated Lens Antenna Using Metamaterials

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.

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

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.

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

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...

Planar metamaterial-based beam-scanning broadband microwave antenna

The broadband directive emission from the use of waveguided metamaterials is numerically and experimentally reported. The metamaterials, which are composed of non-resonant circular complementary closed ring structures printed on a dielectric substrate, are designed to obey the refractive index of a Luneburg lens. An arc array of planar radiating slot antennas placed at the periphery of the lens is used as wave launchers. A prototype of the lens associated with the feed structures has been fabricated using standard lithography techniques. To experimentally demonstrate the broadband focusing properties and directive emissions, far-field radiation patterns have been measured. Furthermore, this metamaterial-based lens can be used to achieve beam-scanning with a coverage of up to 120 °. Far-field measurements agree qualitatively with calculated near-field distributions.

X-band metamaterial-based Luneburg lens antenna

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.

Phase-gradient metasurfaces for beam steerable antennas

Metasurfaces presenting a phase-gradient are designed at 10 GHz and are proposed to steer an antennas radiated beam from broadside towards endfire direction. The metasurfaces are composed of both inductive and capacitive grids and the phase-gradient is achieved by modifying the elements in the inductive grid. Such phase-gradient metasurfaces are utilized as Partially Reflecting Surfaces (PRS) in Fabry-Pérot (FP) leaky-wave antennas (LWAs). Depending on the gradient used, beam steering up to 60° has been observed numerically and verified experimentally.

Analysis of a subwavelength Z-shaped metamaterial

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.

Metamaterial-based 2D multi-beam broadband Luneburg lens antenna

A metamaterial surface composed of non-resonant circular complementary closed ring resonators is designed to obey the refractive index of a Luneburg lens. An array of planar slot antennas placed at the periphery of the lens is used at wave launchers. A prototype of the lens associated with the feed structures has been fabricated using standard printed circuit board (PCB) technology. Measured far-field radiation patterns have shown directive beams in H-plane over the [8 GHz-12 GHz] frequency range. Furthermore, this metasurface lens antenna has demonstrated beam-scanning with a coverage of up to 120°. Far-field measurements agree qualitatively with calculated near-field distributions.