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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Ultra-wide Band In Communications: Performance Analysis And Enhancements

Berksoy, Burak 01 January 2008 (has links)
Over the last ten years, Ultra-Wide Band (UWB) technology has attracted tremendous research attention. Frequency allocation of 3.1-10.6 GHz for UWB application by FCC made it apparent that UWB will be the technology for future wireless high speed communication applications. With the promise of high data rates (high channel capacity), UWB also offers advantages such as communication security, high multi-path resolution, good penetration capability, ability to coexist with other communication schemes in the same band, and finally, circuit simplicity. The theoretical advantages of UWB has made it a great candidate for short distance communications, however, UWB communications have many challenges, for example, sub-nanosecond pulse generation, timing sensitivity of modulation and synchronization, flat antenna performance over a wide bandwidth, effect of existing systems on UWB systems. In order to experiment with various UWB modulation schemes, and to study transmitter and receiver structures, an accurate channel model need be established. In this dissertation, our first contribution is to evaluate and implement two major statistical channel models. The first model is proposed by AT\&T Labs and is in the form of an autoregressive IIR filter. Although this is an accurate channel model to represent UWB behavior, it is proposed before the allocation of 3.1-10.6 GHz frequency band, hence, it could not simulate the correct frequency spectrum. The second model is proposed by Saleh and Valenzuela, which has been widely accepted by UWB community to be the most accurate channel model for UWB systems. Recently disbanded task group 802.15.3a which was assigned to standardize a UWB communication scheme has also accepted the latter model. Our second contribution is to derive optimal pulses for PPM signals. Using the accurate channel model in computer simulations, we experimented on various UWB communication schemes. We found that the traditional UWB pulses being used in pulse position modulated UWB systems did not perform optimally. A set of optimized UWB pulses and the methodology to calculate optimal pulses for any modulation index for PPM systems have been proposed in this dissertation. It is found that the optimal pulse can improve the performance of UWB systems by as much as 0.7 dB. With the PPM pulse optimization, the theoretical performance limits of PPM systems are derived. The third contribution from this dissertation is to design near optimal practical implementable receiver structures. Some of the results obtained from PPM pulse optimization are found to be theoretical and not practical. More practical approach to the receiver structures were needed for industrial interest. We proposed simple sub-optimal receiver structures that are able to perform only a few dB less than the optimal receivers are proposed. These simple, low-cost receiver structures are strong alternatives to the complex traditional optimal receivers.
22

Compact multiple input and multiple output/diversity antenna for portable and mobile ultra-wideband applications

See, Chan H., Hraga, Hmeda I., Noras, James M., Abd-Alhameed, Raed, McEwan, Neil J. January 2013 (has links)
No / This study presents a miniaturised multiple input and multiple output /diversity antenna which is suitable for high data-rate communication systems such as mobile ultra-wideband (UWB). This antenna assembly comprises two identical planar inverted-F antennas, a T-shaped structure connecting them and a finite ground plane. The T-shaped structure improves the impedance matching and suppresses the mutual coupling between the antenna elements over a wider bandwidth than previously reported. The compact envelope dimension of this antenna is 50 x 90 x 7.5 mm(3). Theoretical and experimental S-parameters are illustrated for this antenna that fully cover the UWB operating frequency band of 3.1-10.6 GHz, with a reflection coefficient and mutual coupling better than -10 and -20 dB, respectively. Acceptable agreement is obtained between computed and measured radiation patterns, gains, envelope correlation coefficient and channel capacity loss. The proposed antenna is an attractive candidate to provide pattern diversity and enhance channel capacity in a rich scattering environment.
23

Design of an Ultra-Wide Band based Indoor Positioning System

Li, Jun January 2018 (has links)
In recent years, the indoor positioning system (IPS) has attracted significant interests in both academical research and industrial development. It has seen many applications, such as hostage search and rescue, indoor navigation, and warehouse management, all of which can take advantage of precise positioning. However, in indoor environments, traditional methods, like the Global Positioning System (GPS), are usually either unreliable or incorrect because of the complicated physical characteristics of various objects reflecting and dispersing signals, such as the presence of people, walls, obstructions, and furniture. In contrast to other technologies such as WiFi and Bluetooth, which are not suitable to extract accurate timing information, UWB technology has the potential to reach center-meter level accuracy in indoor positioning. In this thesis, we developed a real-time, low-cost, IPS based on commercial-off-the-shelf UWB transceivers. Both the Two Way Ranging (TWR) and Time Difference of Arrival (TDOA) approaches have been implemented to obtain a target's location. To alleviate the effect of multipath propagation, we detect the presence of outliers by comparing the first path signal level and estimated receiving signal level. Moreover, we have designed the Printed Circuit Board (PCB) and evaluated performance by deploying the system both in a lab environment and in a two-story historical building during the 2018 Microsoft Indoor Localization Competition. The results show that we achieve a 28.9cm 95%-quantile 2D tracking error in the lab environment and a 92cm average tracking error for 3D localization on the Microsoft Indoor Localization Competition site. / Thesis / Master of Science (MSc)
24

Sondeur de canal de propagation multi-capteurs appliqué à la mesure de canal de propagation pour l'Ultra Large Bande (6 GHz - 8.5 GHz) à l'intérieur des bâtiments

El Arja, Hajar 20 September 2010 (has links) (PDF)
Ce manuscrit présente la conception d'un sondeur de canal de propagation en intérieur de bâtiment en contexte Ultra Large Bande ULB. Le sondeur est basé sur une architecture parallèle en réception composée de circuits cinq ports et d'un réseau d'antennes imprimées LTSA (Linear Tapered Slot Antenna). Le sondeur a été réalisé et testé dans la bande de fréquence ULB (6 to 8.5 GHz) alloué par l'ETSI . Les mesures réalisées ont permis d'étudier les directions d'arrivée (DOA) ainsi que le temps d'arrivée des ondes correspondantes aux multi trajets à l'intérieur d'un bâtiment. L'association de la technique cinq-port et de la méthode d'estimation MUSIC (Multiple Signal Classification) permet d'avoir un sondeur à faible coût de réalisation et à haute précision d'estimation. Plusieurs scénarios de propagation sont traités dans le manuscrit que se soit en condition de visibilité (LOS) ou de non visibilité (NLOS)
25

Activity-Based Data Fusion for the Automated Progress Tracking of Construction Projects

Shahi, Arash 05 March 2012 (has links)
In recent years, many researchers have investigated automated progress tracking for construction projects. These efforts range from 2D photo-feature extraction to 3D laser scanners and radio frequency identification (RFID) tags. A multi-sensor data fusion model that utilizes multiple sources of information would provide a better alternative than a single-source model for tracking project progress. However, many existing fusion models are based on data fusion at the sensor and object levels and are therefore incapable of capturing critical information regarding a number of activities and processes on a construction site, particularly those related to non-structural trades such as welding, inspection, and installation activities. In this research, a workflow based data fusion framework is developed for construction progress, quality and productivity assessment. The developed model is based on tracking construction activities as well as objects, in contrast to the existing sensor-based models that are focussed on tracking objects. Data sources include high frequency automated technologies including 3D imaging and ultra-wide band (UWB) positioning. Foreman reports, schedule information, and other data sources are included as well. Data fusion and management process workflow implementation via a distributed computing network and archiving using a cloud-based architecture are both illustrated. Validation was achieved using a detailed laboratory experimental program as well as an extensive field implementation project. The field implementation was conducted using five months of data acquired on the University of Waterloo Engineering VI construction project, yielding promising results. The data fusion processes of this research provide more accurate and more reliable progress and earned value estimates for construction project activities, while the developed data management processes enable the secure sharing and management of construction research data with the construction industry stakeholders as well as with researchers from other institutions.
26

Activity-Based Data Fusion for the Automated Progress Tracking of Construction Projects

Shahi, Arash 05 March 2012 (has links)
In recent years, many researchers have investigated automated progress tracking for construction projects. These efforts range from 2D photo-feature extraction to 3D laser scanners and radio frequency identification (RFID) tags. A multi-sensor data fusion model that utilizes multiple sources of information would provide a better alternative than a single-source model for tracking project progress. However, many existing fusion models are based on data fusion at the sensor and object levels and are therefore incapable of capturing critical information regarding a number of activities and processes on a construction site, particularly those related to non-structural trades such as welding, inspection, and installation activities. In this research, a workflow based data fusion framework is developed for construction progress, quality and productivity assessment. The developed model is based on tracking construction activities as well as objects, in contrast to the existing sensor-based models that are focussed on tracking objects. Data sources include high frequency automated technologies including 3D imaging and ultra-wide band (UWB) positioning. Foreman reports, schedule information, and other data sources are included as well. Data fusion and management process workflow implementation via a distributed computing network and archiving using a cloud-based architecture are both illustrated. Validation was achieved using a detailed laboratory experimental program as well as an extensive field implementation project. The field implementation was conducted using five months of data acquired on the University of Waterloo Engineering VI construction project, yielding promising results. The data fusion processes of this research provide more accurate and more reliable progress and earned value estimates for construction project activities, while the developed data management processes enable the secure sharing and management of construction research data with the construction industry stakeholders as well as with researchers from other institutions.
27

Système de mesure optoélectronique de champs électriques intégrant des capteurs basés sur des microcavités optiques en LiNbO3 / Ultra wide band optoelectronic measurement system of microwave signals using sensors based on optical LiNbO3 microcavities.

Warzecha, Adriana 09 June 2011 (has links)
L’objet de ces travaux de thèse a été de réaliser un système compact et non-invasifde mesure vectorielle de champs électriques. Ce système est dédié aux mesures en espacelibre (diagramme de rayonnement d’antennes) ainsi qu’aux mesures en champ proche(diagnostic de circuits électriques par exemple). Pour ce faire, nous avons proposé unsystème de mesure utilisant d’une part des sondes électro-optique fibrées, dont la partietransductrice est composée d’un guide d’onde en LiNbO3, intégrée dans une cavité Fabry-Pérot. Le cristal non-linéaire induit une modulation de phase d’un faisceau laser de sonde,dépendante du champ électrique à mesurer. La cavité, quant à elle, convertit le signal enmodulation d’amplitude et permet de réduire la taille du capteur grâce à l’augmentationde la longueur effective d’interaction entre l’onde optique et le champ électrique à mesurer.D’autre part l’étude d’un filtrage optique de très grand facteur de qualité associé à unepost-amplification est proposée, dans le but d’accroître d’au moins un ordre de grandeurla sensibilité de mesure. / The aim of this work is to design and realize a compact and non-invasive system dedicatedto vectorial characterization of electric field. The field to be measured can be eitherradiated (for antenna radiation pattern) or guided (for on chip measurement). We herepropose a measurement system including pigtailed electro-optic probe. The transducingdevice is based on a Fabry-Pérot (FP) cavity integrating LiNbO3 waveguide. The nonlinearcrystal induces a phase modulation of a laser probe beam depending on the theelectric field to be characterized. The FP cavity converts the signal into a linear amplitudemodulation and leads to a millimeter sized sensor thanks to the enhancement ofthe effective interactive length between the optical wave and the electric field. The sensorexhibits a sensitivity greater than 0.5 V.m−1.Hz−1/2, a spatial resolution as accurate as100 μm and a frequency bandwidth covering [10 Hz-10 GHz]. Moreover, we here suggesta high quality factor post-filtering of the optical carrier in order to increase the sensitivityof one order of magnitude.
28

DIFFERENTIAL CODE SHIFTED REFERENCE IMPULSE-BASED COOPERATIVE UWB COMMUNICATION SYSTEM

Amjad, Shoaib, Malhi, Rohail Khan, Burhan, Muhammad January 2013 (has links)
Cooperative Impulse Response – Ultra Wideband (IR-UWB) communication is a radio technology very popular for short range communication systems as it enables single-antenna mobiles in a multi-user environment to share their antennas by creating virtual MIMO to achieve transmit diversity. In order to improve the cooperative IR-UWB system performance, we are going to use Differential Code Shifted Reference (DCSR). The simulations are used to compute Bit Error Rate (BER) of DCSR in cooperative IR-UWB system using different numbers of Decode and Forward relays while changing the distance between the source node and destination nodes. The results suggest that when compared to Code Shifted Reference (CSR) cooperative IR-UWB communication system; the DCSR cooperative IR-UWB communication system performs better in terms of BER, power efficiency and channel capacity. The simulations are performed for both non-line of sight (N-LOS) and line of sight (LOS) conditions and the results confirm that system has better performance under LOS channel environment. The simulation results also show that performance improves as we increase the number of relay nodes to a sufficiently large number. / +923214674079 , +923234155044
29

An Analysis of Bluetooth Technology,Features,Future and Security

Ullah, Malik Zaka January 2009 (has links)
In this thesis I present my analysis on various aspects of Bluetooth wireless technology. The Bluetooth technology is relatively new as compared to other technologies and there is huge potential of its growth and practical application. Therefore during in this thesis I try to analysis the current status of this technology and issue which are related to this technology. The first section introduces Bluetooth technology, in which I discussed the architecture of Bluetooth and different terminologies of Bluetooth. In the same section I presented the comparison of Bluetooth with other communication technologies. The main questions I hope to answer in this thesis and also discuss the methodology I employed. The subsequent sections discuss the core technical features and issues of security and interoperability of Bluetooth. In these sections I identify the key aspects of Bluetooth that make it standout from other wireless technologies and point out certain shortcomings of this technology. During this I went through different aspect of Bluetooth technology. Subsequently I present my analysis of the market player’s and user’s perspectives and identify the main drivers and barriers of Bluetooth from a business point of view. Towards the end of this thesis I discuss how this technology can be used to provide some attractive solutions. I demonstrate my ideas by discussing how certain services can be used in future in different scenarios. In my proposed solution I discussed the possibilities and advantages of using Bluetooth technology in university campus to perform different routine tasks and this will beneficial for the university both student and teachers. Keywords: Personal Area Networks, Asynchronous connection Link, Ultra Wide Band, Special Interest group, Bluetooth Technology / Malik Zaka Ullah Phone # 0092 301 8460404,0046738746534 Email : malikzakas@hotmail.com
30

Contribution à la conception de radars géologiques impulsionnels fonctionnant dans un milieu complexe / Contribution to the design of Ground Penetrating Radar operating in a complex environment

Sow, Mouhamed 11 February 2015 (has links)
Ce travail de thèse présente la conception et la réalisation d'une antenne Ultra Large Bande, de faibles dimensions, destinée à une application géoradar fonctionnant dans un milieu complexe pour une bande fréquentielle comprise entre 70 MHz et 1GHz. Cette étude était inscrite dans le cadre d’un projet Européen dénommé NeTTUN (New Technologies for Tunnelling and Underground works) qui a pour but d’améliorer la sécurité du creusement des tunnels. Dans ce projet, le travail demandé était de réaliser un système géoradar comportant une antenne ULB intégrable sur une tête de coupe d’un tunnelier tout en fonctionnant en basses fréquences.Pour réaliser cette antenne en répondant aux différentes contraintes à la fois de dimensions, d’intégration et de rayonnement, une étude d’insertion de l’antenne dans un matériau diélectrique a été effectuée. Ainsi des analyses ont été menées à fois sur la nature des sous-sols rencontrées, du compromis entre fréquences basses et dimensions minimales mais surtout de l’intégrabilité de l’antenne dans une cavité. Cette étude a permis de concevoir une antenne innovante nommé Khorn étant une association de l’antenne K et de la forme « Horn » d’une antenne cornet. Afin d’évaluer la performance de l’antenne Khorn dans son environnement, la tache de rayonnement et la portée de l’ensemble, antenne et source ont été analysées. Des mesures de validation des prototypes fabriquées ont aussi été effectuées. / This work presents the design and the realization of an antenna Ultra Wide Band, of low dimensions, for a GPR application working in a complex environment in a frequency band between 70 MHz and 1GHz. This study was registered within the framework of a European project mentioned NeTTUN (New Technologies for Tunnelling and Underground works) who aims at improving the security of the tunnel driving. In this project, the wanted work was to realize a GPR system containing an integrable antenna ULB on a TBM cutter head while working in low frequencies.To realize this antenna by answering the various constraints of dimensions, integration and radiation, a study of antenna insertion in a dielectric material was realized. So analyses were led for time on the subsoil nature encountered, of the compromise between low frequencies and minimal dimensions and especially the integrability of the antenna in a cavity. This study allowed to realize an innovative antenna named Khorn. The Khorn is an association of the K antenna and the Horn antenna. To estimate the performance of the Khorn in its environment, the footprint and the radar range were studied. Measures of validation of the realized prototypes were also made.

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