Fethi Choubani

Meta-materials applications in thin- film sensing and sensing liquids properties.

This paper is devoted to study one of the most important applications of metamaterials based on Split Ring Resonator (SRR) which is thin-film sensing and sensing liquids properties. We provide a broad overview of thin film deposition methods, depositing the substance material in the gap, under the rings or on the rings. The sensor allows to extract various information about the dielectric properties and the loss from the resonant frequency. The analyses process consists of comparing the resonant shift to characterize the liquid type and the resonant dip to examine the impurities induced in the liquid. Split rings accommodate a wide range of individual preferences and sensing abilities. We demonstrate sensing features of rectangular split rings designed to resonate in the frequency range of 8-12 GHz.

A Family of Directive Metamaterial-Inspired Antennas

A new family of metamaterial-inspired monopole antennas designed for GPS operation is reported. By adding a simple Split-Ring Resonator (SRR) into the near-fleld region of a monopole antenna resonating at 2.45GHz, we have created a second resonance situated in the L1-band (f = 1;537 for example) lower than the monopoles one. At this new resonance, the directivity of the structure was enhanced and its proflle was reduced. Four SRR-conflgurations were considered depending on the orientation of the slot into the resonator. The structure was flrst optimized by adjusting the resonator size and the coupling distance between it and the monopole. Next, the directivity of the structure was improved by adjusting both the SRR-slot position and the coupling distance. Finally, the optimized structure in terms of size and directivity was realized and characterized.

A Planar Reconfigurable Radiation Pattern Dipole Antenna with Reflectors and Directors for Wireless Communication Applications

A planar printed dipole antenna with reflectors and directors, able to steer its radiation pattern in different directions, is proposed for telecommunication applications. Starting from a dual-beam printed dipole antenna achieved by combining two elementary dipoles back to back, and by loading four PIN diodes, three modes of reconfigurable radiation patterns are achieved at the frequency 2.56 GHz thanks to switches states. A prototype of the structure was realized and characterized; an efficiency of 75% is obtained. Simulation and measured results of the results are presented and discussed.

Superdirective and low profile metamaterial-inspired antenna

In this paper, a superdirective and low profile metamaterial-inspired antenna is reported. The proposed structure consists of the association of Split-Ring Resonator (SRR) and a monopole. This antenna of ka = 0.65 size works in the UHF band and exhibits a high directivity of 4.41dBi in the matched bandwidth of 25 MHz (-10dB). Simulated and measured results are presented for the return loss and radiation pattern.

Antenna Ultra Wideband Enhancement by Non-Uniform Matching

In this paper, antenna ultra wideband enhancement by non-uniform matching is proposed. The antenna consisted of a rectangular shaped radiator with two convex circled corners. Simulated results using CST Microwave Studio and measured results of a fabricated antenna concord well to prove that it can operate from about 3.5 GHz to 4.6 GHz and from 7.4 GHz to 12.7 GHz for S11(dB) <-10 dB. In addition, a good impedance matching is noted in the IEEE radar engineering X band range since the return loss coefficient remains below -50 dB value at 9.5 GHz and can reach -45 dB at 11 GHz. A current density comparison at 11 GHz, supporting our argument, between a stepper corner and convex corner demonstrates that the current density can reach 52A/m with a convex corner whereas it does not exceed 33A/m for the antenna with a stepper corners. Radiation patterns at various frequencies and peak gains show clearly interesting features of such antennas.

Design of a multi-band metamaterial-inspired dipole antenna with director element

In this work, we present a multiband metamaterial-inspired antenna. The proposed structure consists of a printed dipole antenna with two Split Ring Resonators (SRRs) and one director element. The addition of the resonators and the director leads to new resonance frequencies lower than that corresponding to the dipole alone with different radiation patterns. Simulation and measured results of return loss and radiation patterns are presented and analysed.

Design of reconfigurable radiation pattern dipole antenna with director and reflector elements for telecommunication systems

A planar printed dipole antenna able to tilt its radiation pattern in different directions is proposed for wireless communication systems. Starting from a dual beam printed dipole antenna working at the 2.45 GHz ISM frequency achieved by combining two elementary dipoles back to back, and by implanting four PIN diodes on the rear side of the substrate, four configurations of directive radiation patterns are easily reached around the frequency 2.64 GHz depending on switches states. A prototype of the basic structure was realized and characterized. Simulation results of the reconfigurable radiation pattern dipole are presented and discussed.

Analysis of a Compact and Superdirective Metamaterial-Inspired Monopole Antenna

The directivity of a metamaterial-inspired compact (0.145λ0) monopole antenna was investigated. The proposed structure is composed of a split-ring resonator (SRR) parasitic element placed in the vicinity of a monopole antenna. Two configurations denoted by A1 and A2 were considered depending on the position of the slot in the SRR element. By analyzing simulated and measured results, the superdirectivity (7.5 dBi for A1 and 9 dBi for A2) of the structure was discussed. It is found that the monopole-SRR and/or ground plane-SRR coupling effects may be responsible for the superdirectivity of the structure.

A coplanar multi-band bow-tie antenna based on split ring resonator

In this paper we propose a new design of multiband coplanar antenna based on split ring resonator (SRR), which can be used for several applications. Into the top layer of antenna substrate, two gaps with the shape of a bow-tie rounded are printed symmetrically. Then, we investigate the properties of SRR to improve the performances of the antenna. The proposed antenna covers many frequency namely 1.93 GHz to 2.12 GHz, 2.63 GHz to 2.7 GHz and 3.26 GHz to 3.53 GHz. Its performances are analyzed in terms of reflection coefficient S11, gain and radiation patterns.

Modeling and simulation of practical metamaterial structures: SRR and HIS structures

Metamaterials have attracted much attention in recent years because of their electromagnetic exquisite proprieties. For this we will introduce in this paper the modeling of a whole structure in metamaterials by equivalent circuit model. We begin by modeling the SRR (Split Ring Resonator), then we model the HIS (High Impedance Surfaces). In order to validate models, we compare the results obtained by an equivalent circuit models with numerical simulation.