Thesis (MPhil)--Stellenbosch University, 2011. / One of the serious problems facing South Africa is that of the provision of adequate low-cost housing for its people. According to Statistics South Africa (2009), 56% of South Africans lived in fully-owned formal dwellings in 2009. Not only does it seem impossible to work away the backlogs, but problems with the standard of construction, location and continuing urbanisation adds to the challenge. International commitments such as the UN’s Millennium Goals put further pressure on government to permanently resolve the issue. Adequate housing is recognised globally as a basic human right. This includes access to running water and sanitation and a safe environment. This study does not aim to investigate, in any way, construction techniques, specific choices of location or other planning-related issues. However, it does try to find a more successful approach to the challenge of the provision of housing given the already stated challenges, combined with, amongst others, the provision of the necessary financing and relevant political processes. The provision of low-cost housing is a wicked problem. This means that it has certain characteristics, including being unique in character and can never be fully resolved. However, within futures studies, systems theory is recognised as one of the more successful ways to address wicked problems. By investigating low-cost housing programmes in Brazil, Argentina and Peru and identifying the elements of systems theory used, it was possible to find pointers to help formulate a set of steps (or actions) to use to address South Africa’s low-cost housing challenge. This research report proposes that, while the challenge of housing provision in a country like South Africa will most probably always be present, it can be alleviated by applying systems thinking to the problem.

Thesis (MBA)--Stellenbosch University, 2009. / ENGLISH ABSTRACT: Globally microfinance is recognised as an important tool in addressing poverty and in building the assets of poor people. Housing microfinance is emerging as an important tool for assisting poor people to improve their housing conditions and to build their asset values. However, microfinancial institutions are perpetually dogged by small scale financially unviable operations. This study seeks to identify the factors that must be present to ensure that a microfinance initiative is able to scale up significantly, and further investigates the Kuyasa Fund as an example of a microfinance organisation that is scaling up. The McKinsey 7S model is used to evaluate the Kuyasa Fund’s plans for scaling up and the shared values, strategy, structure, skills, staffing requirements, style and systems of the Kuyasa Fund is examined in determining the scalability of the Kuyasa Fund. Overall Kuyasa have either already addressed the critical factors in determining its growth or it is in the process of addressing those factors. The biggest strengths of the Kuyasa Fund in its growth plans are the cohesive strategy and in the compelling strategic intent that represents its shared values. However in the medium and long term the greatest challenge is located in the long-term financing and transformation of the Kuyasa Fund from a non-profit to a for-profit entity that has equity shareholders. In achieving this transformation Kuyasa would be required to balance its development objectives with the requirements of equity holders, who will require prescribed rates of return. Preventing mission drifts and achieving scale will be the most important tensions to balance. To mitigate these risks and to set clear guidelines for its operations, the Kuyasa board developed clear criteria for the evaluation of equity partners and the board also set a trajectory for the transformation of Kuyasa to a company. The intention of these is to guide the Kuyasa operation towards the milestones that must be reached before conversion and to set the criteria to select partners. The Kuyasa Fund’s path to conversion from a small niche player limited to one province to a national role player, transformed into an equity holding company will present interesting material for learning about scaling up development efforts, and not just for microfinance. / AFRIKAANSE OPSOMMING: Mikrofinansiering word wêreldwyd erken as ‘n belangrike hulpmiddel in die stryd teen armoede en in die bou van bates vir arm mense. Behuising-mikrofinansiering is besig om as ‘n belangrike instrument na vore te tree om arm mense te help om hul behuisingsomstandighede te verbeter en hul batewaarde op te bou. Mikrofinansieringsinstansies word egter aanhoudend lastig geval deur kleinskaalse besighede wat nie finansieel lewensvatbaar is nie. Hierdie studie poog om die faktore te identifiseer wat teenwoordig moet wees om te verseker dat ‘n mikrofinasieringsinisiatief beduidend kan uitbrei en ondersoek verder die Kuyasa Fund as ‘n voorbeeld van ‘n mikrofinansieringsorganisasie wat tans uitbrei. Die McKinsey 7S-model word gebruik om die Kuyasa Fund se planne vir uitbreiding te evalueer. Die Kuyasa Fund se gedeelde waardes, strategie, struktuur, vaardighede, personeelvereistes, styl en stelsels word ondersoek om die uitbreidingsmoontlikhede van die fonds te bepaal. Oorhoofs het Kuyasa alreeds die kritiese faktore aangespreek wat hul groei bepaal of hulle is in die proses om hierdie faktore aan te spreek. Die grootste sterkpunte van die Kuyasa Fund se uitbreidingsplanne lê in die samehangende strategie en in die gebiedende strategiese rigting wat sy gedeelde waardes verteenwoordig. In die medium- tot langtermyn is die grootste uitdaging geleë in die langtermyn-finansiering en transformasie van die Kuyasa Fund van ‘n niewinsgewende tot ‘n winsgewende entiteit met ekwiteitsaandeelhouers. Ten einde hierdie transformasie deur te gaan, sal van Kuyasa vereis word om sy ontwikkelingsdoelwitte te balanseer met die vereistes van die aandeelhouers, wat hul eie opbrengskoerse sal vereis. Om koersvas hul missie na te streef teenoor die beplande uitbreiding te behaal sal die belangrikste spannings wees om te balanseer. Ten einde hierdie risiko’s te beperk en duidelike riglyne daar te stel vir sy bedrywighede, het die Kuyasa raad duidelike kriteria ontwikkel om ekwiteitsvennote te evalueer. Die raad het ook ‘n vorderingsplan bepaal vir die transformasie van Kuyasa tot ‘n maatskappy. Die bedoeling hiervan is om die Kuyasa bedryf te lei op die pad na mylpale wat bereik moet word voordat omskakeling kan plaasvind en om kriteria daar te stel om vennote te kies. Die Kuyasa Fund se pad na omskakeling van ‘n klein niche speler, beperk tot een provinsie, tot ‘n nasionale rolspeler, wat getransformeer het tot ‘n ekwiteitsmaaskappy sal interessante leergeleenthede bied oor die uitbreiding van ontwikkelingsmaatskappye en nie net op die gebied van mikrofinansiering nie.

This research investigates political risk in the context of service offshoring and the corresponding impact on risk management decisions. The first stage of the study uses the Repertory Grid Technique (RGT), to explore key post-contract political risks experiences within offshore outsourcing activities. Twelve key political risks affecting offshore outsourcing decisions are identified, and the moderating effect of offshoring activity types (BPO, ITO or KPO) on political risk exposure and impact perceptions is highlighted. The research also explores the conditioning effect of industry specific exposure to political risk and enhances the explanatory ability of the Transaction Cost Economics (TCE) constructs, offering a re-operationalization of the political risk component of external uncertainty. The second stage of the research introduces a series of hypotheses between offshoring flows and political risk profiles, and applies multiple regression to analyse political risk affecting offshore activities in low cost countries across contract-based offshoring engagements and FDI. The findings highlight that political risk is a genuine business concern for offshore contract-based outsourcing modalities, and identify concerns with Intellectual Property protection, Quality of Bureaucracy and Corruption as key considerations affecting location decisions in low-cost countries. The research further suggests a positive relationship between strong country level institutional and regulatory systems and high knowledge content in offshoring engagements. From a practical perspective, the research highlights the need for managerial tools to determine diversified firm and industry specific political risk impact on global service outsourcing engagements. The key practical contribution is the development of differentiated political risk typologies that can capture the nuances of external risks in offshoring, allowing for more accurate risk assessment of offshoring decisions.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Sustainability is difficult to achieve in a world where population and economic growth leads to increased production of greenhouse gases, resource depletion and waste generation. Today, the environmental dimension of sustainability, which is more commonly known as the natural environment, and the construction industry are two terms often mentioned together. In Europe, 12.4 % of greenhouse gas emissions are induced by the construction and manufacturing industry (Maydl, 2004). Also, 50 % of the resources extracted are used in the construction industry and more than 25 % of waste generated is construction and demolition waste. In South Africa, the building sector accounts for approximately 23 % of the total greenhouse gas emissions (Milford, 2009). Furthermore, 60 % of investment is made in the residential sector where 33 % of the building stock is the focus of the government’s Housing Programme. It is seen that the construction industry significantly impacts the natural environment and the aim should be to reduce this negative impact. Within the local residential sector, the low-cost housing sector presents potential when it comes to sustainable improvements. Each of the three spheres of sustainability, namely economy, natural environment and society, plays a crucial role in this sector. Various studies have been done on the economical and social fields, but little information exists on the impact low-cost houses have on the environment. A need arises to scientifically quantify the environmental impact hereof, therefore it is chosen as the focus of this study. Various methods in order to determine the environmental impact of the built environment exist globally, but they tend to be complex, are used in conjunction with difficult to understand databases and require expensive software. A need for a local quantification method with which to determine the environmental impact of the built environment, more specifically low-cost housing, has been identified. A simple and easy-to-use analysis-orientated quantification method is proposed in this study. The quantification method is compiled with indicators related to the local conditions; these include Emissions, Resource Depletion and Waste Generation. The end objective is to provide the user with an aggregated total value called the Environmental Impact Index to ease comparison of possible alternatives. The quantification method is developed as a mathematical tool in the form of a partial Life Cycle Assessment which can aid in objective decision making during the conception and design phase of a specific project. Note that only the Pre-Use Phase of the building life cycle is considered during the assessment, but can be extended to include the Use Phase and End-of-Life Phase. The proposed method has the capability of calculating and optimising the environmental impact of a building. Regarding low-cost housing, different housing unit designs can be compared in order to select the best alternative. The quantification method is implemented for two low-cost house design types in this study. Firstly, the conventional brick and mortar design is considered whereafter a Light Steel Frame Building is viewed as an alternative. The model implementation demonstrates that the model operates in its supposed manner. Also, Light Steel Frame Building housing units are shown to be worth investigating as an alternative to the conventional brick and mortar design but should be confirmed with a more accurate Life Cycle Assessment. / AFRIKAANSE OPSOMMING: In ’n wêreld waar toenemende ekonomiese en bevolkingsgroei veroorsaak dat al hoe meer kweekhuisgasse voortgebring word, hulpbronne uitgeput word en groter hoeveelhede rommel geproduseer word, is dit ’n bykans onbegonne taak om volhoubaarheid te probeer bereik. Volhoubaarheid rakende die natuurlike omgewing en konstruksie is twee terme wat vandag dikwels saam genoem word. Ongeveer 12.4 % van die kweekhuisgasse wat in Europa vrygestel word kom uit die konstruksie- en vervaardigingbedrywe (Maydl, 2004). Die konstruksiebedryf gebruik ook bykans die helfte van hulpbronne wat ontgin word en meer as 25 % van rommel word deur konstruksie of sloping produseer. Die Suid-Afrikaaanse boubedryf is verantwoordelik vir 23 % van die totale hoeveelheid kweekhuisgasse wat die land vrystel. Die behuisingsektor, waar die regering aan die hoof van 33 % van eenhede staan, ontvang 60 % van bestaande beleggings (Milford, 2009). Dit is dus duidelik dat die boubedryf ’n negatiewe impak op die natuurlike omgewing het en dat dit van groot belang is om dié situasie te verbeter. In die behuisingsektor het lae-koste-behuising groot potensiaal as dit kom by volhoubaarheid. Volhoubaarheid bestaan uit drie sfere: ekonomie, natuurlike omgewing en sosiaal, en al drie speel ’n betekenisvolle rol in lae-koste-behuising. Daar is reeds verskeie studies aangepak om die ekonomiese en sosiale sfere te beskryf, maar daar is steeds min inligting beskikbaar oor die omgewingsimpak van ’n lae-koste-huis. Dit laat die behoefte ontstaan om hierdie impak te kwantifiseer. Bestaande metodes wat wêreldwyd gebruik word om ʼn omgewingsimpak te bepaal is dikwels besonder kompleks en benodig duur sagteware tesame met ingewikkelde databasisse om dit te implementeer. ’n Behoefte aan ’n plaaslike kwantifiseringsmetode is geïdentifiseer. Hierdie studie stel ’n eenvoudige, gebruikersvriendelike kwantifiseringsmetode bekend. Dit word saamgestel uit faktore wat verband hou met die plaaslike omgewing: Uitlaatgasse, Hulpbronuitputting en Rommelvervaardiging. Uiteindelik word ’n saamgestelde waarde, wat die Omgewingsimpak-indeks genoem word, bereken om vergelyking te vergemaklik. Hierdie kwantifiseringsmetode word aan die hand van ’n gedeeltelike lewenssiklus-analise as ’n wiskundige hulpmiddel ontwikkel. Slegs die eerste fase van ’n gebou se lewenssiklus word beskou tydens hierdie studie, maar dit is moontlik om die ander twee fases in te sluit. Die voorgestelde metode het die vermoë om die omgewingsimpak te bereken en ook te optimeer. Tydens die ontwerpsfase, wanneer belangrike besluite geneem moet word, kan so ’n hulpmiddel van enorme waarde wees om die beste opsie uit verskillende alternatiewe te help identifiseer. Die studie beskou twee tipes behuisingseenhede vir die doel van implementering van die kwantifiseringsmetode: die konvensionele baksteen en mortel metode en alternatiewelik ’n ligte staalraamwerk-gebou. Tydens implementering van die voorgestelde metode, demonstreer die model dat dit werk soos dit veronderstel is om te funksioneer. Verder is getoon dat ’n ligte staalraamwerk-gebou ’n waardevolle alternatief is om te ondersoek, maar dit moet liefs met ’n meer akkurate lewenssiklus-analise bevestig word.

Cette thèse s'inscrit dans le cadre du projet collaboratif FUI RFID AERO dont le leader est Eurocopter. Le but de ce projet est le développement d'un système assurant la traçabilité des différentes pièces d'un aéronef. Cette thèse se focalise sur la conception d'antennes lecteur et de tags RFID UHF faible coût.Deux objectifs sont visés dans le cadre de cette thèse. Le premier est la conception d'antennes pour lecteurs RFID fonctionnant en contact ou à proximité des surfaces métalliques. Nos conceptions sont basées d'une part sur les phénomènes d'ondes constructives en plaçant une surface métallique à un quart de la longueur d'onde. D'une autre part, la conception repose sur l'utilisation de structures AMC. De plus, nous proposons une méthode de réduction de dimensions de cellules AMC. Le second objectif de la thèse est la miniaturisation de tags pour l'identification de pièces essentiellement métalliques. Nous proposons des méthodes de conception de tags miniatures durcis, non détachables ou flexibles ainsi qu'un prototype pour chacune d'entre elles.Enfin, les antennes lecteur et tags développés dans cette thèse, les lecteurs RFID et des systèmes connexes développées par d'autres partenaires ont été mis en œuvre dans un aéronef. Les tests du système complet sont satisfaisants et répond aux objectifs du projet. / This Ph.D thesis is part of the FUI RFID AERO project led by Eurocopter. The aim of this project is to provide a traceability system of the aircraft items. This work focuses on low-cost UHF RFID reader antennas and tags design.Two research axes are developed. The first one is the RFID reader antennas design for metallic surfaces. The designs are based on constructive wave phenomenon by placing a metallic plate at a quarter wavelength of the radiating element. On the other hand, the insertion of AMC structures was also studied. Furthermore, we propose a size reduction technique for AMC structures. The second goal is tag size miniaturization for metallic or non-metallic objects identification. We propose design methods of size miniaturization for hard or flexible tags. Besides, we apply these methods by designing one tag for each family.Finally, the reader antennas and tags proposed in this thesis, the RFID readers and the related systems developed by the others partners were implemented into an aircraft. Tests of the complete system are in good agreement with the expected goals.

La théorie de l'information développée par Claude Shannon (1916 - 2001) met en évidence le fait que pour accroître la capacité d'un canal de transmission, il est préférable d'élargir la bande de fréquences sur laquelle les informations sont émises plutôt que les puissances d'émissions. Cette constatation est le point de départ de nombreux travaux de recherche sur les communications Ultra-Large Bande (ULB) qui ont abouti en 2002 à la création aux Etats-Unis d'une bande fréquence dîtes ULB où aucun mode de communication n'est privilégié. C'est ainsi que 2 années plus tard ont débuté à l'IM2NP des travaux portant sur les communications ULB impulsionnelles, et notamment la conception d'amplificateur faible bruit, de détecteur d'énergie, mais également de générateurs d'impulsions qui est l'élément clé des émetteurs impulsionnels. Ces derniers constituent la base des travaux présentés dans le manuscrit qui se sont déroulés de 2008 à 2011. La nature discontinue des communications impulsionnelles a tout d'abord impliquée l'introduction de nouvelles figures de mérite permettant de mesurer les performances des générateurs d'impulsions. Ensuite, il est question de méthodes de conception permettant de dimensionner des structures fonctionnant aux fréquences en jeu mais également d'en réduire les consommations statiques principalement de fuite, et ce en vue de répondre aux contraintes de consommation des systèmes embarqués. Enfin sont développées 3 architectures de générateurs d'impulsions, chacune permettant de répondre à des contraintes différentes en termes de bande de fréquences, de consommation et de portée. / The information theory developed by Claude Shannon (1916 - 2001) highlights the fact that in order to increase the capacity of a transmission channel, it is preferable to extend the bandwidth used rather than the transmission power. This finding is the starting point of many papers on Ultra-Wideband (UWB) which led to the creation in the United States of UWB band since 2002 where no modulation is privileged. Two years later, many works on Impulsionnal Radio UWB (IR-UWB) communications began at IM2NP including the design of low noise amplifier, power detector, but also pulse generators which is the key element of IR-UWB emitters. These form basis of works presented in the manuscript that took place from 2008 to 2011. The discontinuous nature of communications impulse was first implied the introduction of new figures of merit for measuring performances of pulse generators. Then it deals with design techniques for sizing structures operating at frequencies involved, but also to reduce consumption and especially static leakage to reduce enough power consumption for embedded systems. Finally three architectures of pulse generators are developed, each one responding to different constraints in terms of frequency, consumption and range.

L’évolution actuelle de la société vers un monde de plus en plus numérique et connecté nécessite des liens de communication à la fois haut-débit et bas coûts. A cette fin, les guides d’ondes en plastique proposés ces dernières années visant les bandes de fréquences millimétriques (mm) offrent un compromis performance / coût très attractif.Profitant ainsi de larges bande-passantes de l’ordre de plusieurs gigahertz (GHz), des performances des technologies CMOS avancées aux fréquences mm mais également de tolérances d’assemblage relâchées, des systèmes de communication avec de tels guides d’ondes en plastique pourraient offrir des débits de plusieurs gigabits par seconde (Gb/s) sur des distances de plusieurs mètres de manière abordable.Dans ce travail, la conception d’un guide d’ondes en plastique est tout d’abord présentée en se basant à la fois sur des résultats théoriques et de simulation électromagnétique. Bien que les promesses de faible atténuation aient effectivement été confirmées, certaines limitations du confinement et de la robustesse aux contacts extérieurs sont également apparues. L’ajout d’une mousse protectrice est brièvement investiguée, mais une géométrie innovante de guide présentant des caractéristiques améliorées est principalement détaillée.Des thématiques « systèmes » sont ensuite explorées afin de construire un système de communication utilisant ce nouveau canal de propagation. Une architecture combinant la modulation de phase en quadrature (QPSK) et le multiplexage en fréquence est ainsi introduite. L’interface entre le circuit et le guide d’ondes a par ailleurs été identifiée comme une limitation potentielle à la bande-passante globale du système. Par conséquent, une transition très large-bande a été conçue et testée pour lever ce verrou. De même, en raison des inconvénients des techniques usuelles de démodulation de signaux mm QPSK, une topologie originale utilisant les non-linéarités des oscillateurs à injection a été développée.Enfin, la conception d’un émetteur mm en technologie silicium avancée (CMOS 28 nmFD-SOI) est décrite. Les contributions majeures incluent l’introduction de coupleurs hybrides intégrés à haute-performance ainsi que la réalisation d’un circuit de synchronisation. Celui-ci présente une large plage de capture et permet un fonctionnement à faible bruit de phase lorsque le système est verrouillé sur la cinquième harmonique du signal de référence. Des mesures sur signaux modulés ont également permis de mettre en évidence la capacité de l’émetteur à transmettre des débits très élevés de plusieurs Gb/s. / In a world willfully transitioning to the Digital Age, the thirst for connectivity demands high-speed communication links at low cost. In this context, affordable plastic waveguides have been proposed as a disruptive propagation channel in the millimeter-wave (mmW) range. Benefiting from multi gigahertz (GHz) bandwidths and mmW capabilities of advanced CMOS technologies as well as relaxed assembly tolerances requirements, cost-effective communication systems based on plastic waveguides could offer multi gigabits per second (Gb/s) data rates over several meters distances.In this work, the design of plastic waveguide channels is first discussed using both a theoretical approach and Electromagnetic (EM) simulations. Although low attenuation promises have been confirmed, some limitations are also highlighted, especially as regards confinement ability and robustness to external contacts. Solutions involving foam coating are briefly investigated and an innovative plastic waveguide design demonstrating improved characteristics is introduced.System-level topics are then explored in order to build a communication system using the previously presented channel. A new architecture, which combines Quadrature Phase Shift Keying (QPSK) and frequency multiplexing, is found to be much more suitable. The transition from the circuit to the plastic waveguide has also been identified as a potential bandwidth bottleneck. Consequently, a wideband microstrip to WR-12 transition has been designed. Another limitation concerning the demodulation of QPSK mmW signals is investigated and an original topology using the non-linearities of Injection Locked Oscillators (ILO) has been developed.Finally, the design of a mmW transmitter in an advanced silicon technology node (CMOS 28 nm FD-SOI) is described. Major contributions include the introduction of high-performance integrated hybrid couplers and the realization of a wide locking range synchronization circuit enabling low phase-noise operation when locked on the fifth harmonic of a reference signal. Measurements on modulated signals have validated the transmitter high data-rate capability of several Gb/s.

Cette thèse s’inscrit dans le cadre du projet collaboratif FUI VEADISTA. Le but de ce projet est le développement d’une solution technologique à bas coût pour la veille à distance de personnes fragiles. Cette thèse se focalise sur la conception d’antennes lecteur et d’une étiquette RFID UHF posée sur le corps humain. Deux objectifs principaux sont visés dans ces travaux de thèse. Le premier aborde la conception d’antennes pour lecteurs RFID, le second aborde la conception d’une antenne large bande, pour une étiquette RFID, adaptée au corps humain. Les objectifs à atteindre pour l’antenne lecteur sont : un champ rayonné à polarisation circulaire, un gain élevé, faible coût de fabrication et faible épaisseur. Pour atteindre ces objectifs, une topologie d’anneau fente miniaturisé par une méthode itérative de repliement d’anneau associée à un réflecteur incluant un AMC à cellules élémentaires réduites sont employés. Le second objectif de la thèse est la conception d’une antenne large bande, pour une étiquette RFID, capable de minimiser l’influence du corps humain sans sacrifier la distance de lecture tout en restant faible coût. Un modèle électromagnétique d’avant-bras humain est utilisé comme support de conception de l’antenne tag large bande. Enfin le système RFID complet incluant, l’étiquette, l’antenne lecteur et le lecteur RFID ont fait l’objet de tests fonctionnels pour préparer les tests cliniques sur patient. / This thesis was initiated within the VEADISTA project. The main goal of this project was to develop a cost effective technological remote care system for fragile person. The main focus of this thesis is on antenna design for RFID reader and also for RFID tags in contact with human body. For the reader antenna the criteria are: a circularly polarized radiated field, high gain, cost effectiveness and small thickness. To achieve these objectives, a miniaturized slot ring topology obtained by an iterative method of ring folding associated with a reflector including a reduced unit cells AMC are used. For the tag the objective is to design a broadband antenna, by minimizing the influence of human body without affecting the reading scope. The tag is needed to also be cost effective. An electromagnetic model of human forearm is used as the broadband tag antenna design support. Ultimately, the functionality of the complete system including a tag and a reader have been tested.

Le secteur des communications sans fil a connu un essor considérable, soutenu par l’évolution des "smartphones" et par le développement des réseaux de capteurs sans fil et de l’Internet des Objets (connu en anglais sous le nom ‘IoT’ pour Internet of Things). Les applications actuelles visent l’autonomie énergétique des objets communicants et nécessitent la conception de circuits intégrés pouvant assurer à la fois un fonctionnement à hautes performances et à moindre coût. L’une des principales fonctions des systèmes de communications radiofréquences (RF) est la génération de fréquence, assurée par l’oscillateur. De nombreux efforts de conception sont ainsi nécessaires afin d’assurer les performances requises par les nouvelles applications sans fil. Nos travaux de recherche ont pour objectif de proposer une méthode de conception d’oscillateurs agiles à faible consommation au sein des systèmes d’émission-réception RF. Le travail s’est focalisé sur l’étude et l’optimisation des éléments constitutifs d’un oscillateur LC passif en technologie CMOS et sur la proposition d’une méthode de conception. La méthode proposée peut être exploitée pour différentes structures d’oscillateurs afin d’optimiser leurs performances essentiellement en termes de consommation de puissance et de bruit de phase. Cette méthode a été appliquée pour implémenter plusieurs VCOs en technologie CMOS. Une série de mesure sous pointes a permis de valider leur fonctionnement. La suite de ce travail de thèse est consacrée à la proposition d’une nouvelle topologie d’oscillateur LC reconfigurable à base d’inductance active dédiée aux applications multistandards faible coût / The rapid growth of the Internet of Things (IoT) applications and the wireless sensor networks boosts the need for low cost and low power radiofrequency (RF) transceivers. The voltage-controlled oscillator (VCO) is an essential building block of several RF transceivers. Design tradeoffs have been very stringent in terms of power consumption, phase-noise, area and tuning range. In this context, the aim of this work is to propose a design method, aiming to optimize the VCO design and to improve its performances essentially in terms of power consumption and phase noise.The first part of this thesis sets a study of the elements of passive LC oscillators in CMOS technology. The second part presents a complete design method, aiming to optimize the LC-VCO performance regarding the phase noise and power consumption. The evaluation of the proposed method is carried out with some test-cases in full CMOS technology. Many RF LC-VCOs have been implemented and measured. The final part of this thesis presents a new tunable VCO suitable for multi-standards applications. The frequency tuning of the VCO is ensured using an active inductor based on CMOS inverters. The desired bandwidth can be selected while achieving low surface area and low power consumption.

O desenvolvimento técnico da eletrônica, a contínua redução do tamanho dos receptores GNSS, associada à diminuição do consumo de energia, transformaram estes produtos em alguns circuitos integrados ou apenas pequenos chips do tamanho de um botão de uma camisa. Desta forma pode-se promover a sua integração com inúmeros dispositivos eletrônicos. A associação com os telefones celulares foi principalmente impulsionada pelo mandato de aprimoramento dos serviços 911 (E911) da Federal Communications Commission (FCC) nos Estados Unidos, exigindo que todas as operadoras de telefonia móvel daquele país fornecessem a localização com boa precisão das chamadas de emergência. Esta necessidade estimulou a produção dos chips em larga escala e, portanto, a diminuição do custo e a sua popularização. Desta maneira quase que em sua totalidade, os telefones celulares são hoje fabricados com receptores GPS, o que torna estes dispositivos uma das fontes mais baratas de se obter o Geoposicionamento. Acontece que existe uma lacuna na literatura quanto à precisão e a exatidão das coordenadas fornecidas por estes equipamentos. O presente trabalho visa, através de testes estatísticos e da comparação com outros receptores GPS e métodos, quantificar estes valores e propor uma metodologia para melhorar tal posicionamento. Para conseguir o objetivo, a estrutura do Sistema Operacional do telefone foi modificada de tal modo que fosse possível o acesso às observáveis do chipset do GPS embarcado e convertidos para o padrão RINEX de arquivamento de dados brutos. Os testes foram executados com o equipamento original e com o equipamento modificado com a instalação de uma antena externa e mostraram que com a utilização da medida de fase da portadora o equipamento pode fornecer o posicionamento com uma precisão média de 0,069m, com o desvio padrão de 0,047m e erro planimétrico de posicionamento máximo de 0,218m e mínimo de 0,004m. / The technical development of electronics, the continuous reduction in the size of GNSS receptors, allied with the energy consumption decrease, transformed these products into some integrated circuits or in small Chips as small as size of a button of a shirt. In this way one can promote its integration with countless electronic devices. The association with cell phones was mainly driven by the mandate to enhance services 911 (E911) of the Federal Communications Commission (FCC) in the United States, requiring that all mobile carriers of that country provide all the emergency calls location with good accuracy. So as to fulfill this necessity, the production of Chips in a large scale has been stimulated and therefore the decrease in cost and its popularity. In this way almost in its entirety, cell phones are now manufactured with GPS receivers, which makes these devices one of the cheapest sources to obtain the geopositioning. It turns out that there is a gap in the literature about how precise and accurate the coordinates provided by these equipments can be. This thesis aims through statistical tests and comparison with other GPS receivers and methods, quantify these values and propose a methodology to improve such positioning. To achieve the objective, the structure of the phone\'s operating system was modified in such a way that it was possible to access the embedded GPS Chipset observables and then converted into the RINEX standard raw data file. The tests were carried out with the original equipment and with the modified ones, with an external antenna installation which showed that using the phase measure of the carrier, the equipment can provide a positioning with an average accuracy of 0, 069m, with a default deviation of 0, 047m and a maximum planimetric positioning error of 0, 218m and a minimum of 0, 004m.