Mourad Nedil

Novel butler matrix using CPW multilayer technology

In this paper, a novel 4 times 4 two-layer Butler matrix based on a broad-band two-layer slot-coupled directional coupler is presented and implemented at 5.8 GHz using coplanar waveguide technology. With the slot-coupled directional coupler, the proposed matrix was designed without using any crossovers as used in conventional Butler matrices, which leads to significant size reduction and loss minimization. To examine the performance of the proposed matrix, experimental prototypes of the multilayer directional coupler and the Butler matrix were fabricated and measured. Furthermore, a four-antenna array was also designed and fabricated at 5.8 GHz and then connected to the matrix to form a beamforming antenna system. As a result, four orthogonal beams at -45deg, -15deg, 15deg, and 45deg are produced. Measured results on the entire system agree well with the theoretical predictions, validating the proposed design

ULTRA WIDEBAND CPW-FED APERTURE ANTENNA WITH WLAN BAND REJECTION

In this paper, we present a new ultra wideband antenna design with band rejection for UWB applications. A CPW-fed circular patch radiates through a circular aperture, which ensures wideband impedance matching and stable omnidirectional pattern over an UWB frequency range, from 3GHz to 10.6GHz. In order to avoid interference

MIMO-UWB Channel Characterization Within an Underground Mine Gallery

Multiple input multiple output-ultrawide band (MIMO-UWB) systems are experimentally evaluated for underground mine high-speed radio communications. Measurement campaigns using two different antenna configurations have been made in an underground gold mine. Furthermore, two scenarios, which are the line of sight (LoS) and the non-LoS (NLoS), i.e., taking into account the mining machinery effect, are distinguished and studied separately. In fact, the channel is characterized in terms of coherence bandwidth, path loss, shadowing, channel correlation, and capacity. Results reveal how antenna array configuration affects main channel parameters and suggest that mining machinery presence substantially affects both received power and time dispersion parameters within the underground mine and should, therefore, be considered when assessing the performance of in-gallery wireless systems. Moreover, it is shown that the MIMO-UWB takes benefit of the large spreading bandwidth and the multipath propagation environment to increase the channel capacity.

Fluidic patch antenna based on liquid metal alloy/single-wall carbon-nanotubes operating at the S-band frequency

This letter describes the fabrication and characterization of a fluidic patch antenna operating at the S-band frequency (4 GHz). The antenna prototype is composed of a nanocomposite material made by a liquid metal alloy (eutectic gallium indium) blended with single-wall carbon-nanotube (SWNTs). The nanocomposite is then enclosed in a polymeric substrate by employing the UV-assisted direct-writing technology. The fluidic antennas specimens feature excellent performances, in perfect agreement with simulations, showing an increase in the electrical conductivity and reflection coefficient with respect to the SWNTs concentration. The effect of the SWNTs on the long-term stability of antennas mechanical properties is also demonstrated.

Design of UWB filter -antenna with notched band at 5.8GHz

In this paper, an UWB integrated filter-antenna system with notched band at 5.8 GHz has been presented. The design of the proposed integrated filter-antenna is based on cascading an UWB notched filter with an UWB antenna. The two parts of the system have already been matched to each others. The antenna-filter has a small size (68 × 27mm2). The system bandwidth meets the UWB requirements.

ANALYSIS AND DESIGN OF AN ULTRA WIDEBAND DIRECTIONAL COUPLER

Abstract—In this paper, a novel wideband directional coupler using coplanar waveguide multilayer slot-coupled technique is presented and implemented. The coupler uses two coplanar waveguide lines etched on two layers and coupled through an hexagonal slot etched on the common ground plane located between these layers. Firstly, conformal mapping techniques were used to obtain analytic closed-form expressions for the evenand odd-mode characteristic impedances. Secondly, using this approach, a new design of the directional coupler was performed. Both simulation and experimental results show a good performance in terms of bandwidth.

Novel Butler matrix using CPW multi-layer technology

In this paper, a novel 4 times 4 two-layer Butler matrix based on a broad-band two-layer slot-coupled directional coupler is presented and implemented at 5.8 GHz using coplanar waveguide technology. With the slot-coupled directional coupler, the proposed matrix was designed without using any crossovers as used in conventional Butler matrices, which leads to significant size reduction and loss minimization. To examine the performance of the proposed matrix, experimental prototypes of the multilayer directional coupler and the Butler matrix were fabricated and measured. Furthermore, a four-antenna array was also designed and fabricated at 5.8 GHz and then connected to the matrix to form a beamforming antenna system. As a result, four orthogonal beams at -45deg, -15deg, 15deg, and 45deg are produced. Measured results on the entire system agree well with the theoretical predictions, validating the proposed design

BANDWIDTH WIDENING TECHNIQUES FOR DIRECTIVE ANTENNAS BASED ON PARTIALLY REFLECTING SURFACES

The directivity bandwidth of Fabry-Perot directive antennas is first evaluated theoretically. Then, different techniques are proposed to widen the directivity bandwidth of antennas using Partially Reflecting Surfaces. The bandwidths obtained with the proposed solutions are compared to the bandwidth of a classical Fabry- Perot directive antenna.

Transport properties of a highly conductive 2D Ti3C2Tx MXene/graphene composite

We report on the elaboration and transport properties of a sandwich like 2-dimensional Ti3C2Tx MXene/Graphene composite through alternating electrospray of MXene and graphene materials. The structural and electrical properties were systematically investigated with respect to the graphene content. The surface roughness of the samples has found to decrease considerably after the graphene integration. Electrical measurements show a clear trend to increase in both electrical conductance and Hall carrier mobility with respect to the graphene concentrations, and even reach the values of 9.5 × 104 S/cm and 54.58 cm2/V s, respectively, for only 2.5 wt. % of graphene, rendering this MXene based composite one of the most electrically conductive to date.

High gain cylindrical dielectric resonator with superstrate for broadband millimeter-wave underground mining communications

This paper presents a new broadband and high gain dielectric resonator for millimeter-wave underground communications systems. The proposed antenna is composed of a superstrate, an aperture coupled feed, an intermediate substrate and a cylindrical dielectric resonator. This antenna is designed to cover the ISM frequency band (57 GHz-65 GHz). This antenna was numerically designed using CST microwave Studio simulation software package. Simulated results show that the antenna has good performances especially in terms of bandwidth and gain. A bandwidth of 18.4% at the centered frequency of 59.83 GHz and a gain of 11 dB over the entire ISM bandwidth have been achieved. An enhancement of gain by 9 dB has been obtained at the frequency of 60 GHz compared to a single DRA. With these performances, this antennas is suitable for wireless underground communication systems.