Développement d'un réseau d'antennes à formation de faisceaux basé sur de nouvelles Matrices de Butler.

Dans cette thèse, nous présentons une nouvelle topologie d'un réseau d'antenne à formation de faisceaux basée sur nouvelle matrice de Butler. L'étude comporte trois volets portant respectivement sur la conception d'une antenne fente large bande, d'un réseau d'antennes et d'une matrice de Butler pour assurer la formation des faisceaux. Dans un premier temps, on présente une étude d'antenne à fente alimentée par une ligne de transmission coplanaire. Le principe de fonctionnement de cette structure d'antenne repose sur le couplage électromagnétique alimenté par une ligne coplanaire. L'étude paramétrique de cette structure faite par le simulateur Momentum a permis de comprendre mieux le fonctionnement et l'influence de chaque paramètre sur le comportement de l'antenne, soit le réglage de l'impédance, l'efficacité ou la fréquence de résonance. Cette antenne a fourni de bonnes performances en terme de largeur de bande qui est très utile pour les systèmes de communication sans fil dans la bande des 5.8 GHz. Plusieurs géométries de l'élément rayonnant ont été développées pour permettre d'élargir la bande passante de cette antenne. D'ailleurs, une nouvelle technique d'alimentation, combinant les deux types d'excitation inductive et capacitive, a été développée. Ceci a permis d'atteindre une largeur de bande de 30% au lieu de 8% avec une seule excitation. Dans l'étape suivante nous présentons une optimisation de cette antenne en utilisant la technique broches EBG à l'élément simple de l'antenne ainsi pour le réseau à 2 et 3 éléments a permis d'augmenter l'efficacité jusqu'à 95 % sans perturber ni la bande passante des antennes ni la forme du diagramme du rayonnement. Tous ces prototypes d'antennes ont été fabriqués et validés. Dans la troisième étape, nous introduisant le traitement RF (matrice de Butler) appliqué aux antennes développées auparavant. Deux structures de la matrice de Butler ont été développées, et fabriquées et validées. La première matrice conçue est à base de la technologie ligne à fente. Un nouveau coupleur hybride et un croisement en technologie ligne à fente ont été également et ont offert de bonnes performances en terme de couplage et d'isolation. Les faisceaux simulés et mesurés obtenus montrent que la matrice offre de bonne performances. La deuxième structure de la matrice de Butler a été développée en technologie CPW multicouche qui a comme objectif d'éliminer tous croisement entre les lignes coplanaires. Cette exigence, nous a permis de concevoir une nouvelle structure de coupleur CPW directionnel multicouche et à large bande. La combinaison de ce coupleur et du coupleur directionnel dans la matrice a permis d'éviter l'utilisation des croisements. Cette solution offre de bonnes performances à la matrice en termes de pertes et de compacité. L'assemblage du réseau avec la nouvelle matrice a été fait pour réaliser une antenne à faisceaux. Les résultats obtenus ont montré de meilleures performances en termes de directivité et de contrôle de diagramme de rayonnement

Progress Research on Wireless Communication Systems for Underground Mine Sensors

This chapter will study the application of UWB and MIMO techniques in wireless sensor networks. Hence, a channel characterization of the wireless underground channel is essential for the proliferation of communication protocols for wireless sensor network

The Design of a 360°-Switched-Beam-Base Station Antenna

The concept of switched-beam antenna (SBA) systems covering an area of 360° for wireless base station applications is presented. First, a reconfigurable pattern antenna (RPA), which is composed of an omnidirectional slot-antenna array surrounded by an active cylindrical frequency selective surface (FSS), is studied. The behavior of FSS is controlled by PIN diodes which are able to divide the Azimuth plane into six sectors from one common source. Unfortunately for a sector antenna, a huge number of diodes are required which complicates the structure in terms of efficiency and complexity. However, a simple and an efficient SBA configuration based on a hexagonal Fabry-Pérot cavity leaky wave antenna (FPC LWA) arrays is proposed as a solution for RPA problems. A sector-directive beam is generated from a simple patch antenna embedded inside a resonant Fabry-Pérot cavity with specific dimensions which have an influence on beamwidth and radiation efficiency. To increase more sectorization level and channel’s capacity, the proposed sector in FPC LWA arrays can be divided into three subsectors by using an active high-impedance surface (HIS). As a conclusion, SBA based on FPC LWA is the most suitable solution for future wireless communications

Millimeter-Wave Massive MU-MIMO Performance Analysis for Private Underground Mine Communications

In this article, a performance analysis of millimeter wave (mmWave) massive multiuser multiple-input and multiple-output (MU-MIMO) channel within an underground mine is performed. The analysis is based on channel measurements conducted at 28 GHz using a base station of 64 virtual antenna elements serving multiple users. Channel characteristics such as large-scale path loss, time dispersion, coherence bandwidth and sum-rate capacity are reported and evaluated. The results indicate that multislope path loss model is better suited for precise prediction of path loss across various propagation segments within the mining gallery. The time dispersion analysis reveals that the underground mine channel does not cause significant time dispersion, as 90% of the root-mean-square (rms) delay spreads are below 4 ns. In addition, it was found that the rms delay spread is not dependent on the propagation distance. The study on sum-rate capacity highlights the potential of employing massive MIMO technology to improve the channel’s spectral efficiency. The analysis reveals that the capacity, with eight active users, can reach up to 33.54 bit/s/Hz. The outcomes of this article offer valuable insights into the propagation properties of underground mine environment, which is characterized by rich-scattering and irregular topology

A nested square-shape dielectric resonator for microwave band antenna applications

In this paper, a nested square-shape dielectric resonator (NSDR) has been designed and investigated for antenna applications in the microwave band. A solid square dielectric resonator (SSDR) was modified systematically by introducing air-gap in the azimuth (ϕ-direction). By retaining the square shape of the dielectric resonator (DR), the well-known analysis tools can be applied to evaluate the performance of the NSDR. To validate the performance of the proposed NSDR in antenna applications, theoretical, simulation, and experimental analysis of the subject has been performed. A simple microstrip-line feeding source printed on the top of Rogers RO4003 grounded substrate was utilized without any external matching network. Unlike solid square DR, the proposed NSDR considerably improves the impedance bandwidth. The proposed antenna has been prototyped and experimentally validated. The antenna operates in the range of 12.34GHz to 21.7GHz which corresponds to 56% percentage bandwidth with peak realized gain 6.5dB. The antenna has stable radiation characteristics in the broadside direction. A close agreement between simulation and experimental results confirms the improved performance of NSDR in antenna applications

A Compact Implantable MIMO Antenna for High-Data-Rate Biotelemetry Applications

This article presents a low-profile multiple-input–multiple-output (MIMO) implantable antenna system, including a capsule endoscopy and a scalp implantation at medical implant communication service (MICS) band (402–405 MHz), and industrial, scientific, and medical (ISM) band (433.1–438.8 MHz). It consists of two elements with an edge-to-edge gap of 0.0018λg and overall dimensions of π×(5.65)2×0.13 mm 3 and is placed on a 0.13 mm-thick RO3010 ( ϵr=10.2 and tan δ=0.0022 ) substrate. The antenna is integrated with batteries, sensors, and electronic components in two different types of implantable devices (capsule and flat-type devices). The simulation result shows that the antenna has a fractional bandwidth (FBW) of 33.9%, a maximum realized gain of −30 dBi, and isolation of more than 26 dB. The fabricated prototype is measured in a saline solution and minced pork meat. The measured results are found in good accordance with simulations. The antenna parameters are calculated and showed a significant independence between the radiators. A link budget is estimated to be 78 Mb/s for a distance of 20 m. Thus, the proposed antenna is considered as a promising solution for high-data-rate medical applications such as capsule endoscopy, live surgeries, and other biomedical applications where the high data rate is required

Ambipolar operation of hybrid SiC-carbon nanotube based thin film transistors for logic circuits applications

We report on the ambipolar operation of back-gated thin film field-effect transistors based on hybrid n-type-SiC/p-type-single-walled carbon nanotube networks made with a simple drop casting process. High-performances such an on/off ratio of 105, on-conductance of 20 μS, and a subthreshold swing of less than 165 mV/decades were obtained. The devices are air-stable and maintained their ambipolar operation characteristics in ambient atmosphere for more than two months. Finally, these hybrid transistors were utilized to demonstrate advanced logic NOR-gates. This could be a fundamental step toward realizing stable operating nanoelectronic devices

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 (4GHz). 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 antenna’s mechanical properties is also demonstrated