Le besoin incessant de débits toujours plus élevés dans les systèmes de télécommunications a un impact sur tous les éléments composant la chaine de transmission. Ainsi, pour faire face à l’augmentation croissante du volume de données échangées à travers le monde, le développement de nouvelles sources optiques semi-conductrices est absolument nécessaire. La modulation directe de lasers nanostructurés constitue une alternative bas coût et à faible consommation énergétique qui permettra de remplacer progressivement les diodes lasers à puits quantiques actuelles. De nombreux efforts en recherche ont été consacrés au cours des dernières années en vue d’améliorer les performances dynamiques des lasers nanostructurés notamment en terme de bande passante, de facteur de couplage phase-amplitude (facteur α) et de dérive de fréquence (chirp). Pour les applications aux très grands réseaux et systèmes de communication, la croissance d’îlots ou de fils quantiques déposés sur substrat InP permet de réaliser des dispositifs nanostructurés émettant dans le proche infra-rouge autours de 1550 nm. Dans ce mémoire, la dynamique de modulation des lasers nanostructuré est étudiée en régime de modulation directe. Les caractéristiques analysées comprennent: la modulation en amplitude (AM) et en fréquence (FM), le chirp, et les réponses en régime grandsignal. Grâce à une approche semi-analytique, il est démontré que la bande passante et l’amortissement sont fortement limités par les phénomènes de capture et de relaxation des porteurs de charge dans les nanostructures. Afin d’étudier les propriétés du facteur α et du chirp, un nouveau modèle dynamique a été proposé, prenant en compte la contribution à l’indice optique des porteurs de charge dans des états hors résonance. Il est ainsi montré que, contrairement au cas des lasers à puits quantiques, le facteur α dépend fortement du courant de pompe et de la fréquence de modulation. Le facteur α reste constant à basses fréquences (<0,1 GHz) et supérieur aux valeurs obtenues à hautes fréquences (au-delà de quelques GHz) à partir de la technique FM/AM. Ces caractéristiques sont essentiellement attribuées aux contributions des porteurs dans les états hors résonance. Les simulations montrent que le facteur α peut être réduit en augmentant la séparation énergétique entre l’état fondamental résonant (GS) et les états hors résonance. En particulier, un effet laser sur 1’état excité des nanostructures (ES) constitue une solution prometteuse pour améliorer les performances dynamiques, en accroissant notamment la bande passante de modulation et en réduisant le facteur α d’environ 40%. Les techniques d’injection optique sont également intéressantes pour régénérer les performances dynamiques des lasers. Le couplage phase-amplitude et le gain optique y sont substantiellement modifiés via le contrôle de l’amplitude et du désaccord en fréquence du faisceau injecté. Dans ce cadre, ce travail propose une nouvelle technique dérivée de la méthode Hakki-Paoli, permettant de mesurer, sous injection optique, le facteur α à la fois en dessous et au-dessus du seuil. Les lasers à cascade quantique (QCL) sont basés sur des transitions électroniques inter-sous-bandes dans des hétérostructures à puits quantiques. Ces lasers présentent une bande passante (AM) relativement de quelques dizaines de GHz et sans résonance ce qui est prometteur pour les transmissions en espace libre. De manière surprenante, les calculs montrent que les QCL présentent une largeur de bande FM extrêmement large de l’ordre quelques dizaines de THz, environ trois ordres de grandeur supérieure à la largeur de bande AM. L’injection optique dans ces lasers présente les mêmes avantages que ceux procurés dans les lasers à transitions interbandes. Des désaccords positifs ou négatifs en fréquence augmentent notamment la largeur de la bande passante. / High performance semiconductor lasers are strongly demanded in the rapidly increasing optical communication networks. Low dimensional nanostructure lasers are expected to be substitutes of their quantum well (Qwell) counterparts in the next-generation of energy-saving and high-bandwidth telecommunication optical links. Many efforts have been devoted during the past years to achieve nanostructure lasers with broad modulation bandwidth, low frequency chirp, and reduced linewidth enhancement factor. Particularly, 1.55-μm InP-based quantum dash (Qdash)/dot (Qdot) lasers are preferable for long-haul transmissions in contrast to the 1.3-μm laser sources. In this dissertation, we investigate the dynamic characteristics of InPbased nanostructure semiconductor lasers operating under direct current modulation, including the amplitude (AM) and frequency (FM) modulation responses, the linewidth enhancement factor (also known as α-factor), as well as large-signal modulation responses. Using a semi-analytical analysis of the rate equation model, it is found that the modulation bandwidth of the quantum dot laser is strongly limited by the finite carrier capture and relaxation rates. In order to study the α- factor and chirp properties of the quantum dot laser, we develop an improved rate equation model, which takes into account the contribution of carrier populations in off-resonant states to the refractive index change. It is demonstrated that the α-factor of quantum dot lasers is strongly dependent on the pump current as well as the modulation frequency, in comparison to the case of Qwell lasers. The α-factor remains constant at low modulation frequencies (<0.1 GHz) and higher than the value derived at high modulation frequencies (beyond several GHz) from the FM/AM technique. These unique features are mostly attributed to the carrier populations in off-resonant states. Further simulations show that the α-factor can be reduced by enlarging the energy separation between the resonant ground state (GS) and off-resonant states. Lasing from the excited state (ES) can be a promising alternative to enhance the laser’s dynamic performance. The laser exhibits a broader modulation response and the α-factor can be reduced by as much as 40%. The optical injection technique is attractive to improve the laser’s dynamical performance, including bandwidth enhancement and chirp reduction. These are demonstrated both theoretically and experimentally. The phase-amplitude coupling property is altered as well in comparison with the free-running laser and the optical gain depends on the injection strength and the frequency detuning. This work proposes a new method derived from the Hakki-Paoli method, enabling to measure the α-factor of semiconductor lasers under optical injection both below and above threshold. In addition, it is demonstrated theoretically that the α-factor in nanostructure lasers exhibits a threshold discontinuity, which is mainly attributed to the unclamped carrier populations in the off-resonant states. It is a fundamental limitation, preventing the reduction of the α-factor towards zero. Quantum cascade (QC) lasers rely on intersubband electronic transitions in multi-quantum well heterostructures. QC lasers show flat broadband AM response (tens of GHz) without resonance, which constitutes promising features for free-space communications. Surprisingly, calculations show that the QC laser exhibits an ultrabroad FM bandwidth on the order of tens of THz, about three orders of magnitude larger than the AM bandwidth. Optically injection-locked QC lasers also exhibit specific characteristics by comparison to interband semiconductor lasers. Both positive and negative frequency detunings enhance the modulation bandwidth.

Orientador: Luiz Carlos Kretly / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T12:34:11Z (GMT). No. of bitstreams: 1 Silva_MauricioWeberBenjoda_M.pdf: 7910629 bytes, checksum: ba689f61e380994adce43b3aad0b347c (MD5) Previous issue date: 2009 / Resumo: O desenvolvimento de chaves MEMS (Micro Electro Mechanical System) de RF, usando os conceitos e a tecnologia de placa de circuito impresso (PCB) é objeto desta pesquisa. Foram fabricadas micro-chaves na configuração paralela, sobre guias de onda coplanares (CPW). Recentemente, suas aplicações vêm sendo direcionadas a circuitos mais sofisticados, onde são monoliticamente integrados com outros componentes de RF, como antenas e deslocadores de fase. As chaves desenvolvidas são projetadas para operar com baixa tensão de ativação, e fabricadas usando a técnica surface micromachining, que consiste em construir as estruturas em camadas de filmes finos, e removendo as camadas sacrificiais até a liberação da parte flexível do dispositivo. Neste trabalho é apresentada toda a metodologia do projeto, incluindo as simulações eletromecânicas e eletromagnéticas das chaves MEMS em PCB, bem como s caracterizações. As chaves mostraram desempenho compatível com dispositivos equivalentes comerciais de RF, apresentando larga banda de operação de 1,8 - 18 GHz. Tendo em vista o desempenho físico e operacional dos dispositivos fabricados, essa tecnologia mostra-se viável com tecnologias dominadas localmente e se aplica tanto para Rádio Freqüência como para micro-ondas. / Abstract: The development of RF MEMS (Micro Electro Mechanical System) switches, using the concepts and technology of Printed Circuited Board (PCB) is the object of this research. Micro switches in the shunt configuration through the Coplanar Waveguide (CPW) were manufactured. Recently, its applications have been directed to more sophisticated circuits, which are monolithic integrated with other RF components such as antennas and phase shifters. The developed switches are designed to operate with low actuation voltage and manufactured using the surface micromachining technique, which consists to build the structures in thin film layers, and removing the sacrificial layers to the release of the flexible device part. In this work is presented all the methodology of the project, including the electromechanical and electromagnetic simulations of the MEMS switches on PCB, as well as the characterizations. The switches had shown compatible performance when compared with equivalent RF devices available in the market, showing broadband operation from 1,8 - 18 GHz. Due the physical and operational performance of the manufactured devices, this technology shows viable with locally known technologies and feasible for applications in both Radio Frequency and microwave. / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

To overcome the hurdles associated with space management and security controls in a housing system, research was projected to study and analyze the necessary factors of accomplishment. Over time, different processes were observed and reviewed to make this a possible deal. Various residents were interviewed on the daily constraints in parking and managing their vehicles within their housing premises. The reported daunting concern was majorly the gate access and personal hunts for the space to keep the individual resident’s cars. Every resident would always have to stop and hoot at the housing gate for the assigned personnel to check and open the gate. While this would waste every resident’s time, the visitors even face more delay often time. Hitherto, car access and parking constraint become a thing of worry that no one would want to engage the housing service anymore. The interest has got dwindled. And to re-awaken the high patronage of the housing system, a gap must be bridged with an immediate solution to space management with a gating system. These were subsequently given a classical thought, while a prototype solution was demonstrated and reviewed with the various residents of some selected housing. This received a high welcoming embracement and was beckoned to be made real by the logical heuristic. At this point, nothing was further considered than using the Internet of things (IoT) technology to implement Vehicular Access Management for the control and integration of intended space provisioning in any housings. Consequently, the number plate of every vehicle becomes the automatic access tag and would be used for security control within the housing location. Vehicles’ numbers would be captured and used to manage the residents passing through the automated gating system. With it, records would be made for all permitted residents and the visitors that own a car. Thus, a proper arrangement would be allotted accordingly, as provisioned by the gating system administrator. However, to allegories the above-proffered solution, this project work is divided into six sections. The introductory section introduces the project rationale, lists the objectives, explores related works, and introduces how IoT and vehicular systems can be merged. The second section delves into these vehicular systems. It introduces the Automatic License Plate Recognition System (ALRP) and the Raspberry Pi and highlights the merits of the Integrated Vehicular Access Security System. Open-CV and machine learning are also introduced. Section three covers the solution design, while section four is the implementation phase. Section five covers the testing and implementation of the solution. The final section summarizes the project. The project successfully models an automated solution for the security of tenants and vehicle users against unauthorized access to residential estates and buildings.

Orientador: Alexandre César Rodrigues da Silva / Resumo: Transmissão de dados sem fio tem se tornado cada vez mais presente no dia a dia, devido a comodidade da não utilização de cabos, bem como pela maior mobilidade propiciada. Este trabalho aborda duas tecnologias de comunicação sem fio atuais: Identificação por Radiofrequência (RFID) e Bluetooth, destacando suas principais características e apresenta o protótipo de um circuito que efetua a leitura de tags fixadas em objetos, por meio de um leitor RFID e, posteriormente, transmite a identificação dessas a um smartphone, por meio da tecnologia Bluetooth. Com o propósito de ilustrar aplicações do protótipo construído, foram desenvolvidos dois softwares para smartphones Android: um de controle de medicamento de idosos e outro para auxiliar deficientes visuais nas aulas práticas laboratoriais. Durante o desenvolvimento do trabalho, testes foram realizados para se verificar o alcance de leitura do leitor RFID utilizado. Também foram realizados testes com a tecnologia Bluetooth, verificando-se a distância máxima de conexão e transmissão/recepção de dados entre o protótipo desenvolvido e um smartphone. / Abstract: Wireless data transmission has become increasingly present in everyday life, because the convenience of not using cables, as well as the greater mobility afforded. This paper addresses two current wireless communication technologies: Radio Frequency Identification (RFID) and Bluetooth, highlighting its main characteristics and presents the prototype of a circuit that performs the reading tags attached to objects by means of an RFID reader and later transmits the identification to such a smartphone, using Bluetooth technology. In order to illustrate prototype built applications, they developed two software for Android smartphones: one for the elderly medicine control and another to assist the visually impaired in the laboratory classes. During the development work, tests were conducted to verify the read range of the RFID reader used. Also with Bluetooth technology tests were performed, checking the maximum distance connection and transmission/reception of data between the developed prototype and a smartphone. / Mestre

Tato diplomová práce se zabývá problematikou plazmového nanášení bioaktivních keramických povlaků hydroxylapatitu s využitím technologie radio-frekvenčně buzeného indukčně vázaného plazmatu. Cílem bylo optimalizovat proces a nanést kompaktní hydroxylapatitové povlaky na substráty z titanové slitiny Ti6Al4V. Nanesené vzorky byly následně podrobeny analýzám povrchové drsnosti, mikrostruktury a fázového složení. Ze získaných výsledků byly vyvozeny závěry, které byly srovnány s dalšími odbornými pracemi zabývajícími se příbuznou problematikou.

Les nano-applications utilisant des faisceaux d'ions focalisés nécessitent des sources d'ions à haute brillance avec une faible dispersion en énergie (ΔE) ce qui permet une excellente résolution latérale et un courant d'ions suffisamment élevé pour induire des vitesses d'érosion raisonnables et des rendements élevés d'émission électronique et ionique. Les objectifs de cette thèse sont le développement d'une source d'ions basée sur l'impact électronique ayant une brillance réduite Br de 10³ – 10⁴ A m⁻² sr ⁻ ¹ V⁻ ¹, une dispersion en énergie ΔE ≲ 1 eV et un choix polyvalent d'ions. Le premier concept évalué consiste à focaliser un faisceau d'électrons à une énergie de 1 keV entre deux électrodes parallèles distant de moins d'un millimètre. Le volume d'ionisation « micrométrique » est formé au-dessus d'une ouverture d'extraction de quelques dizaines de µm. En utilisant un émetteur d'électrons LaB₆ et une pression de 0.1 mbar dans la région d'ionisation, Br est proche de 2.10² A m⁻² sr ⁻ ¹ V ⁻ ¹ avec des tailles de source de quelques µm, des courants de quelques nA pour Ar⁺/Xe⁺/O₂ ⁺ et une dispersion en énergie ΔE < 0.5 eV. La brillance réduite Br est encore en dessous de la valeur minimum de notre objectif et la pression de fonctionnement très faible nécessaire pour l'émetteur LaB₆ ne peut être obtenue avec une colonne d'électrons compacte, donc ce prototype n'a pas été construit.Le deuxième concept de source d'ions évalué est basé sur l’idée d’obtenir un faisceau ionique à fort courant avec une taille de source et un demi-angle d’ouverture similaire aux résultats du premier concept de source, mais en changeant l’interaction électron-gaz et la collection des ions. Des études théoriques et expérimentales sont utilisées pour l’évaluation de la performance de ce deuxième concept et de son utilité pour les nano-applications basées sur des faisceaux d'ions focalisés. / High brightness low energy spread (ΔE) ion sources are needed for focused ion beam nano-applications in order to get a high lateral resolution while having sufficiently high ion beam currents to obtain reasonable erosion rates and large secondary electron/ion yields. The objectives of this thesis are: the design of an electron impact ion source, a reduced brightness Br of 10³ – 10⁴ A m⁻² sr⁻ ¹ V⁻ ¹ with an energy distribution spread ΔE ≲ 1 eV and a versatile ion species choice. In a first evaluated concept an electron beam is focussed in between two parallel plates spaced by ≲1 mm. A micron sized ionisation volume is created above an extraction aperture of a few tens of µm. By using a LaB₆ electron emitter and the ionisation region with a pressure around 0.1 mbar, Br is close to 2.10² A m⁻² sr ⁻ ¹ V ⁻ ¹ with source sizes of a few µm, ionic currents of a few nA for Ar⁺/Xe⁺/O₂ ⁺ and the energy spread being ΔE < 0.5 eV. The determined Br value is still below the minimum targeted value and furthermore the main difficulty is that the needed operation pressure for the LaB₆ emitter cannot be achieved across the compact electron column and therefore a prototype has not been constructed. The second evaluated source concept is based on the idea to obtain a high current ion beam having a source size and half-opening beam angle similar to the first concept, but changing the electron gas interaction and the ion collection. Theoretical and experimental studies are used to evaluate the performance of this second source concept and its usefulness for focused ion beam nano-applications.

dreimal im Jahr erscheinende Zeitschrift über aktuelle Themen der TU Chemnitz

dreimal im Jahr erscheinende Zeitschrift über aktuelle Themen der TU Chemnitz

This work presents a robust dual band local positioning system (LPS) working in the 2.4GHz and 5.8GHz industrial science medical (ISM) bands. Position measurement is based on the frequency-modulated continuous wave (FMCW) radar approach, which uses radio frequency (RF) chirp signals for propagation time and therefore distance measurements. Contrary to state of the art LPS, the presented system uses data from both bands to improve accuracy, precision and robustness. A complete system prototype is designed consisting of base stations and tags encapsulating most of the RF and analogue signal processing in custom integrated circuits. This design approach allows to reduce size and power consumption compared to a hybrid system using off-the-shelf components. Key components are implemented using concepts, which support operation in multiple frequency bands, namely, the receiver consisting of a low noise amplifier (LNA), mixer, frequency synthesizer with a wide band voltage-controlled oscillator (VCO) having broadband chirp generation capabilities and a dual band power amplifier. System imperfections occurring in FMCW radar systems are modelled. Effects neglected in literature such as compression, intermodulation, the influence of automatic gain control, blockers and spurious emissions are modeled. The results are used to derive a specification set for the circuit design. Position estimation from measured distances is done using an enhanced version of the grid search algorithm, which makes use of data from multiple frequency bands. The algorithm is designed to be easily and efficiently implemented in embedded systems. Measurements show a coverage range of the system of at least 245m. Ranging accuracy in an outdoor scenario can be as low as 8.2cm. Comparative dual band position measurements prove an effective outlier filtering in indoor and outdoor scenarios compared to single band results, yielding in a large gain of accuracy. Positioning accuracy in an indoor scenario with an area of 276m² can be improved from 1.27m at 2.4GHz and 1.86m at 5.8GHz to only 0.38m in the dual band case, corresponding to an improvement by at least a factor of 3.3. In a large outdoor scenario of 4.8 km², accuracy improves from 1.88m at 2.4GHz and 5.93m at 5.8GHz to 0.68m with dual band processing, which is a factor of at least 2.8. / Die vorliegende Arbeit befasst sich mit dem Entwurf eines robusten lokalen Positionierungssystems (LPS), welches in den lizenzfreien Frequenzbereichen für industrielle, wissenschaftliche und medizinische Zwecke (industrial, scientific, medical, ISM) bei 2,4GHz und 5,8GHz arbeitet. Die Positionsbestimmung beruht auf dem Prinzip des frequenzmodulierten Dauerstrichradars (frequency modulated continuous wave, FMCW-Radar), welches hochfrequente Rampensignale für Laufzeitmessungen und damit Abstandsmessungen benutzt. Im Gegensatz zu aktuellen Arbeiten auf diesem Gebiet benutzt das vorgestellte System Daten aus beiden Frequenzbändern zur Erhöhung der Genauigkeit und Präzision sowie Verbesserung der Robustheit. Ein Prototyp des kompletten Systems bestehend aus Basisstationen und mobilen Stationen wurde entworfen. Fast die gesamte analoge hochfrequente Signalverarbeitungskette wurde als anwendungsspezifische integrierte Schaltung realisiert. Verglichen mit Systemen aus Standardkomponenten erlaubt dieser Ansatz die Miniaturisierung der Systemkomponenten und die Einsparung von Leistung. Schlüsselkomponenten wurden mit Konzepten für mehrbandige oder breitbandige Schaltungen entworfen. Dabei wurden Sender und Empfänger bestehend aus rauscharmem Verstärker, Mischer und Frequenzsynthesizer mit breitbandiger Frequenzrampenfunktion implementiert. Außerdem wurde ein Leistungsverstärker für die gleichzeitige Nutzung der beiden definierten Frequenzbänder entworfen. Um Spezifikationen für den Schaltungsentwurf zu erhalten, wurden in der Fachliteratur vernachlässigte Nichtidealitäten von FMCW-Radarsystemen modelliert. Dazu gehören Signalverzerrungen durch Kompression oder Intermodulation, der Einfluss der automatischen Verstärkungseinstellung sowie schmalbandige Störer und Nebenschwingungen. Die Ergebnisse der Modellierung wurden benutzt, um eine Spezifikation für den Schaltungsentwurf zu erhalten. Die Schätzung der Position aus gemessenen Abständen wurde über eine erweiterte Version des Gittersuchalgorithmus erreicht. Dieser nutzt die Abstandsmessdaten aus beiden Frequenzbändern. Der Algorithmus ist so entworfen, dass er effizient in einem eingebetteten System implementiert werden kann. Messungen zeigen eine maximale Reichweite des Systems von mindestens 245m. Die Genauigkeit von Abstandsmessungen im Freiland beträgt 8,2cm. Positionsmessungen wurden unter Verwendung beider Einzelbänder durchgeführt und mit den Ergebnissen des Zweiband-Gittersuchalgorithmus verglichen. Damit konnte eine starke Verbesserung der Positionsgenauigkeit erreicht werden. Die Genauigkeit in einem Innenraum mit einer Grundfläche von 276m² kann verbessert werden von 1,27m bei 2,4GHz und 1,86m bei 5,8GHz zu nur 0,38m im Zweibandverfahren. Das entspricht einer Verbesserung um einen Faktor von mindestens 3,3. In einem größeren Außenszenario mit einer Fläche von 4,8 km² verbessert sich die Genauigkeit um einen Faktor von mindestens 2,8 von 1,88m bei 2,4GHz und 5,93m bei 5,8GHz auf 0,68m bei Nutzung von Daten aus beiden Frequenzbändern.

The transverse emittance is one of the most important quantities which characterize the quality of an electron source. For high quality experiments low beam emittance is required. By means of theoretical considerations and simulation calculations we have studied how the emittance of the Rossendorf superconducting radio-frequency photoelectron source (SRF gun) can be minimized. It turned out that neither a solenoid magnet nor the effect of space charge forces is needed to create a pronounced emittance minimum. The minimum appears by just adjusting the starting phase of the electron bunch with respect to the RF phase of the gun in a suitable way. Investigation of various correlations between the properties of the beam particles led to an explanation on how the minimum comes about. It is shown that the basic mechanism of minimization is the fact that the longitudinal properties of the particles (energy) are strongly influenced by the starting phase. Due to the coupling of the longitudinal and transverse degrees of freedom by the relativistic equation of motion the transverse degrees of freedom and thereby the emittance can be strongly influenced by the starting phase as well. The results obtained in this study will be applied to minimize the emittance in the commissioning phase of the SRF gun.