• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 71
  • 21
  • 7
  • 6
  • 4
  • 4
  • 3
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 159
  • 57
  • 30
  • 29
  • 29
  • 25
  • 23
  • 22
  • 21
  • 21
  • 20
  • 19
  • 18
  • 17
  • 17
  • 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.
111

Contribution à l'étude du stress cellulaire potentiellement induit par les ondes millimétriques

Nicolas Nicolaz, Christophe 26 November 2009 (has links) (PDF)
Pour faire face à la saturation du spectre électromagnétique en matière de communications sans fil, les groupes industriels dominant le marché développent de nouveaux appareils de télécommunications sans fil, qui offriront un débit très élevé combiné à une meilleure confidentialité. Ces systèmes fonctionneront dans des bandes de fréquences autour de 60 GHz, naturellement absentes du spectre électromagnétique environnemental, ce qui suscite des interrogations légitimes quant à leur innocuité. Ce travail de thèse porte sur l'analyse des effets potentiels des rayonnements millimétriques sur la physiologie de la cellule. Nous avons tout d'abord étudié les effets des ondes millimétriques par le biais d'études in vitro, en utilisant différents modèles de cultures de cellules humaines, exposés à différents temps et à différentes fréquences, notamment celles correspondantes à des résonances de groupement moléculaires, comprises entre 57 et 64 GHz. Nous avons étudié l'impact potentiel de ces ondes sur un organite cellulaire, le réticulum endoplasmique, connu pour être sensible à son environnement et impliqué dans de nombreuses pathologies. Nous avons ensuite étudié les effets de la variation de puissance sur des processus physiologiques concernant le réticulum endoplasmique mais aussi sur la synthèse de protéines spécifiques liées à la réponse inflammatoire. Enfin, par la technique de puces à ADN, nous avons réalisé une approche transcriptomique à haut débit, portant sur l'ensemble du génome, afin de déterminer l'existence de gènes cibles sensibles à des expositions aux ondes millimétriques. Plusieurs gènes candidats ont été sélectionnés et serviront de biomarqueurs.
112

Integrated Antennas and Active Beamformers Technology for mm-Wave Phased-Array Systems

Biglarbegian, Behzad 26 March 2012 (has links)
In this thesis, based on the indoor channel measurements and ray-tracing modeling for the indoor mm-wave wireless communications, the challenges of the design of the radio in this band is studied. Considering the recently developed standards such as IEEE 802.15.3c, ECMA and WiGig at 60 GHz, the link budget of the system design for different classes of operation is done and the requirement for the antenna and other RF sections are extracted. Based on radiation characteristics of mm-wave and the fundamental limits of low-cost Silicon technology, it is shown that phased-array is the ultimate solution for the radio and physical layer of the mobile millimeter wave multi-Gb/s wireless networks. Different phased-array configurations are studied and a low-cost single-receiver array architecture with RF phase-shifting is proposed. A systematic approach to the analysis of the overall noise-figure of the proposed architecture is presented and the component technical requirements are derived for the system level specifications. The proposed on-chip antennas and antenna-in-packages for various applications are designed and verified by the measurement results. The design of patch antennas on the low-cost RT/Duroid substrate and the slot antennas on the IPD technologies as well as the compact on-chip slot DRA antenna are explained in the antenna design section. The design of reflective-type phase shifters in CMOS and MEMS technologies is explained. Finally, the design details of two developed 60 GHz integrated phased-arrays in CMOS technology are discussed. Front-end circuit blocks such as LNA, continuous passive reflective-type phase shifters, power combiner and variable gain amplifiers are investigated, designed and developed for a 60 GHz phased-array radio in CMOS technology. In the first design, the two-element CMOS phased-array front-ends based on passive phase shifting architecture is proposed and developed. In the second phased-array, the recently developed on-chip dielectric resonator antenna in our group in lower frequency is scaled and integrated with the front-end.
113

Sistema de videovigilancia mediante radioenlaces para el distrito de Santiago de Cusco

Asencios Rodriguez, Aldo Williams, Vergaray Mayo, Manuel Accel January 2015 (has links)
El presente proyecto de investigación tiene como finalidad presentar una solución a la problemática que se tiene en la Región Cusco, Provincia Cusco, Distrito de Santiago. Como se detalla el presente proyecto, existen diversos factores que determinan el tipo de problemática en el ámbito de seguridad que presenta el distrito de Santiago, por ejemplo, lugares de riñas frecuentes, puntos de mayor incidencia delictiva, lugares con nula o escasa iluminación, lugares de concentración de alcohólicos o drogadictos, todo esto a raíz de la falta de coordinación entre las instituciones a quienes les compete el ámbito de seguridad. Santiago es uno de los distritos principales de la ciudad del Cusco, por lo tanto, planteamos la propuesta de tener un sistema de seguridad integrado, el cual consiste en emplear cámaras de videovigilancia que estarán interconectadas mediante el uso de radio enlaces hacia un punto central o centro de control, desde dicho lugar se podrán monitorear las principales calles y avenidas con altos índices mayor incidencia. Se espera como resultado, disminuir los índices de inseguridad que actualmente presenta el distrito, con ayuda de la propuesta planteada.
114

Vital Sign Radar Redesign : Further Development of a Compact, Highly integrated 60 GHz Radar for Human Vital Sign Monitoring

Dalati, Fares, Martinez Lopez, Pablo Enrique January 2017 (has links)
Nowadays, thanks to the modern technologies, the human being has been able todevelop new techniques to solve problems present in the past. Regarding the medicalfield, it is common to use several apparatus in order to measure the vital signs. Themain drawback about the traditional methods employed for this purpose is that theyare invasive towards the patient. However, in this thesis it has been developed afurther design of a radar system so as to be able to measure these vital signs in awireless way. Based on a 60 GHz frequency modulated continuous wave radar chip, it has been ableto increase the performance of the measurements by adding a second radar chip.Because of this new feature, the radar system is now having a better precision byprocessing greater data matrix to analyse the targets positions and theirmeasurements. In addition, an enhanced MCU has been incorporated in order toavoid performance bottlenecks because it is necessary to handle the processing of thedata received by the two radar chips. Lastly, reducing the sweeping time (periodbetween the lowest frequency broadcast to linearly reach the highest frequencybroadcast) from 20 ms the previous design to 1 ms, which requires higher samplingrate to cover the fast sweep and provide higher flow of information that leads to fasterdetection process. A 3D design of the prototype has been designed to show the physical appearance itwould have once entering in production. The result is a compact and highlyintegrated radar system which will be able to monitor the heart beating andrespiration frequency of a human being in a range of ten meters.
115

Lokalizace uvnitř budov pomocí technologie LoRa / LoRa-based indoor localization

Šimka, Marek January 2021 (has links)
This diploma thesis focuses on possible utilization of LoRa (Long Range) technology for indoor localization purposes. In this thesis, the starter kit SK-iM282A is used to create a LoRa-based wireless link in the 2.4 GHz ISM band. Main attention is focused on the experimental localization using the RSSI method in the various transmission environments, including a description of the localization principle, the procedure of processing the measured data and the evaluation of localized coordinates. The rightness of the proposed measurement setup and methodology is verified by extensive measurements in various environments and compared with state-of-the-art article.
116

Channel modeling for 60 GHZ body area networks / Modélisation de canal pour réseaux corporels à 60 GHZ

Mavridis, Theodoros 28 August 2015 (has links)
Les environnements intelligents et l’homme connecté semble être la prochaine évolution des télécommunications sans fil. En effet, le développement des nouvelles bandes de fréquence millimétriques permettront de créer des communications haut débit et de nouveaux types d’environnements, les Wireless Body Environment Networks, où les utilisateurs auront la possibilité d’interagir avec l’environnement. Pour développer ces environnements, il est nécessaire d’étudier les mécanismes de propagation et les canaux de communication sans fil autour du corps humain. Cette thèse analyse les canaux de propagation pour les réseaux corporels à 60 GHz et plus particulièrement trois scenarios: (i) la propagation entre une station de base externe et un noeud placé à proximité du corps (off-body) ; (ii) la propagation entre deux noeuds portés sur le corps (on-body) ; (iii) la communication entre une station de base externe et un noeud tenu porté par la main de l’utilisateur (near-body). Un modèle de canal numérique est proposé et implémenté pour modéliser la propagation off-body en environnement intérieur. Le modèle est basé sur le standard IEEE 802.11ad et une solution de la diffraction d’une onde plane incidente sur un modèle cylindrique du corps humain. Le modèle est développé pour deux polarisations orthogonales et les performances d’une communication WiGig sont étudiées via le bit error rate. La propagation on-body est étudiée pour deux différentes configurations: avec et sans ligne de vue directe. Ces scenarios mènent à des solutions analytiques différentes: l’équation de Norton et l’onde rampante. Ces solutions sont obtenues en utilisant des modèles de corps simplifiés et ont été validées expérimentalement. De plus, une méthode permettant d’améliorer le bilan de liaison entre deux dispositifs portés sur le corps en utilisant des plaques métalliques réduisant les pertes de propagation. Cette technique a été illustrée théoriquement en utilisant les équations de Millington. Une campagne de mesure a été effectuée sur un modèle de corps plat ayant les propriétés électriques de la peau humaine. Il a été montré que cette méthode permet d’augmenter le bilan de liaison de 20 dB. La région near-body s’étendant de 5 à 30 cm du corps humain est étudiée. Il s’agit de la région correspondant à la portée de main. Un algorithme numérique est proposé pour modéliser la présence d’un utilisateur dans un environnement intérieur. Un modèle statistique a aussi été proposé. Il a été montré que la distribution spatiale du champ suit une Two-Wave Diffuse Power distribution. / The smart environments and the connected human seems to be the future of wireless communications. The development of new frequency bands in the millimeter range will allow us to create high data rate communications which will led to the Wireless Body Environment Networks. In this kind of scenarios, it is expected that the user and the environment will interact. In order to develop such new applications, it is necessary to first study the propagation mechanisms and then, the communication channel underlying body centric environments. This thesis treats of channel models for 60 GHz Body Area Networks and more particularly of three kinds of scenarios: (i) the communication between an external base station and a worn node (off-body); (ii) the communication between two worn nodes (on-body); the communication between an external base station and a hand-held device (near-body). An indoor off-body channel model is numerically proposed and implemented. The model is based on the IEEE 802.11ad indoor standard channel at 60 GHz and a fast computation solution of the scattering of a plane wave by a circular cylinder. The model is developed for two orthogonal polarizations and the communications performances are studied. The on-body propagation is studied for two different configurations: line-of-sight and non-line-of-sight communications on the body. These scenarios led to different solutions for the channel knowing as, respectively, Norton’s equations and creeping formulations. These solutions are obtained using simplified geometries which has been experimentally validated. Further, in order to improve the propagation on the human body, a technique using metallic plates has been proposed. This technique has been theoretically studied using Milligton’s equations and experimentally assessed on a flat phantom with the properties of the human skin. The proposed method allows to save up to 20 dB. Finally, the near-body communication scenario has been introduced and studied. The near-body region is extended from 5 to 30 cm away of the user body which corresponds to the arm’s reach and models a handheld device. A numerical algorithm has been proposed to model indoor near-body environments. Also, a special has been given to statistical body shadowing. It has been shown that the fading follows a Two-Wave Diffuse Power distribution.
117

Non-Planar 3D Printed Radar Lenses

Bukht, Ali January 2021 (has links)
The primary motivation behind this research was to determine whether 3D printed lenses printed out using the non-planar technique can help achieve better beam intensity for a 60 GHz printed-circuit-board based radar and consequently improve radar efficiency. Non-planar printing is a new development in the 3D printing industry. In the non-planar printing method, the printer is moving simultaneously in all X, Y and Z-axis. This process prints with curved layers, which helps achieve a smoother surface. For this, a newly developed version of the Slic3r, specifically called non-planar Slic3r, was used. The modelled lens was imported into this Slic3r software. The G-Code was generated, and using it, non-planar lenses were printed along with planar lenses for comparison purpose. The lenses printed out using the non-planar technique were not perfectly smooth as was thought initially. Both planar and non-planar lenses measurements were taken in a watchful environment, and the measurements were later compared. The comparison of measurements showed that the non-planar lens did not show any noticeable gain in the intensity over planar lenses. The conclusion, however, is limited to the frequency range around 60 GHz, and in the case of higher frequencies, the result may change
118

Green and Highly Efficient MIMO Transceiver System for 5G Heterogenous Networks

Al-Yasir, Yasir I.A., Abdulkhaleq, Ahmed M., Ojaroudi Parchin, Naser, Elfergani, Issa T., Rodriguez, J., Noras, James M., Abd-Alhameed, Raed, Rayit, A., Qahwaji, Rami S.R. 23 July 2021 (has links)
Yes / The paper presents the general requirements and an exemplary design of the RF front-end system that in today's handset is a key consumer of power. The design is required to minimize the carbon footprint in mobile handsets devices, whilst facilitating cooperation, and providing the energy-efficient operation of multi-standards for 5G communications. It provides the basis of hardware solutions for RF front-end integration challenges and offers design features covering energy efficiency for power amplifiers (PAs), Internet of Things (IoT) controlled tunable filters and compact highly isolated multiple-input and multiple-output (MIMO) antennas. An optimum design requires synergetic collaboration between academic institutions and industry in order to satisfy the key requirements of sub-6 GHz energy-efficient 5G transceivers, incorporating energy efficiency, good linearity and the potential for low-cost manufacturing. A highly integrated RF transceiver was designed and implemented to transmit and receive a picture using compact MIMO antennas integrated with efficient tunable filters and high linearity PAs. The proposed system has achieved a bit error rate (BER) of less than 10-10 at a data rate of 600 Mb/s with a wireless communication distance of more than 1 meter and power dissipation of 18-20 mW using hybrid beamforming technology and 64-QAM modulation. / 10.13039/100010665-H2020 Marie Skodowska Curie
119

Dual-Polarized Highly Folded Bowtie Antenna with Slotted Self-Grounded Structure for Sub-6 GHz 5G Applications

Alibakhshikenari, M., Virdee, B.S., See, C.H., Shukla, P., Moghaddam, S.M., Zaman, A.U., Shafqaat, S., Akinsolu, M.O., Liu, B., Yang, J., Abd-Alhameed, Raed, Falcone, F., Limiti, E. 26 September 2021 (has links)
Yes / In this paper, a novel dual-polarized highly-folded self-grounded Bowtie antenna that is excited through I-shaped slots is proposed for applications in sub-6GHz 5G multiple-input-multiple-output (MIMO) antenna systems. The antenna consists of two pairs of folded radiation petals whose base is embedded in a double layer of FR-4 substrate with a common ground-plane which is sandwiched between the two substrate layers. The ground-plane is defected with two I-shaped slots located under the radiation elements. Each pair of radiation elements are excited through a microstrip line on the top layer with RF signal that is 180° out of phase with respect to each other. The RF signal is coupled to the pair of feedlines on the top layer through the I-shaped slots from the two microstrip feedlines on the underside of the second substrate. The proposed feed mechanism gets rid of the otherwise bulky balun. The Bowtie antenna is a compact solution with dimensions of 32×32×33.8 mm3. Measured results have verified that the antenna operates over a frequency range of 3.1–5 GHz and exhibits an average gain and antenna efficiency in the vertical and horizontal polarizations of 7.5 dBi and 82.6%, respectively.
120

Performance Comparison of Harmonically Tuned Power Amplifiers at 28 GHz in SiGe BiCMOS

Phan, Diem Thanh 07 March 2017 (has links)
As the demand for wireless electronics is increasing, more and more gadgets are connected wirelessly and devices are being improved constantly. The need of the new research and development for advance electronics with high performances is the priority. The data transfer rates are improved for faster communication and better efficiency is to reduce the battery consumption in handheld devices. This thesis presents three single-stage power amplifiers (PAs): class-AB, class-F and inverse class-F (class-F-1) at 28 GHz. The PAs have identical input networks: input matching, base DC feed, and base stabilizing networks. At the load side, there is a different load network for each PA. Class-AB PA load network has a single inductor with a parasitic capacitor to create a resonance at 28GHz. Class-F PA load network is composed of a parallel network (one LC tank in series with an inductor) and a series network (one 3f0-resonance LC tank in series with a capacitor) to create a multi-resonance load network. Class-F-1 load network is composed of a parallel network (two LC tank in series with an inductor) and a series network (one 2f0-resonance LC tank in series with a capacitor) to have a multi-resonance network. The main purpose of using multi-resonance load networks in class-F and class-F-1 is to shape the collector currents and voltages in order to achieve the highest efficiency possible. The chosen bias point is VCE=2.3V and ICE~12mA. As the results, class-AB PA achieves the peak PAE of 44%, 15 dBm OP-1dB, >19 dBm Psat , and 10 dB Gp. Class-F PA achieves the peak PAE of 46%, 14.5 dBm OP-1dB, ~18 dBm Psat , and 10 dB Gp. Class-F-1 PA achieves the peak PAE of 45%, 15.1 dBm OP-1dB, >18 dBm Psat , and 10 dB Gp.. In order to compare the linearity performances among three PA classes, a two-tone signal and a modulated signal with different modulation schemes (QPSK, 16QAM, 64QAM, and 256QAM) are applied to the PAs to produce IM3, ACPR, and EVM. After the analysis and comparison on efficiency and linearity, class-F PA gives the highest efficiency but has the worst linearity while class-AB has the best linearity but has the worst efficiency among three. Class-F-1 PA results lies in the middle of two other classes in term of efficiency and linearity. / Master of Science

Page generated in 0.0305 seconds