Ce travail consiste à développer un système convertissant une partie de l’énergie mécanique du cœur en électricité pour alimenter les stimulateurs cardiaques de nouvelle génération, implants sans sonde ni batteries implantés directement dans la cavité cardiaque. Après études de différentes sources d’énergies et concept associés, l’option liée à la pression sanguine, appliquant sur une partie souple du boîtier de l’implant des efforts transmis à un transducteur interne les convertissant en électricité, s’est révélée la plus prometteuse. Cette solution présente les avantages principaux suivants par rapport aux systèmes inertiels usuels : grande densité de puissance, adaptabilité au rythme cardiaque et potentiel de miniaturisation. Un boîtier ultra-souple électro-déposé de 10 µm d’épaisseur en forme de soufflet a été modélisé, fabriqué et caractérisé, validant ainsi le concept de récupérateur proposé. Un transducteur électrostatique novateur (3D multicouche à peignes interdigités et à chevauchement hors-plan), étudié par des modélisations analytiques et numériques, est en cours de fabrication. Selon l’électronique associée, ce transducteur promet une grande densité d’énergie extraite. Un transducteur piézoélectrique micro-usiné en forme de spirale et à électrodes micro-structurées, est également présenté. Les défis spécifiques des spirales dontla flexibilité permet d’augmenter l’énergie mécanique d’entrée sont étudiés notamment par simulation numériques, et des prototypes ont été micro-fabriqués et caractérisés. Au final, une énergie de 3 µJ/cm3/cycle est obtenue et de nombreuses perspectives d’amélioration permettent d’envisager une puissance au moins 10 fois supérieure. / This work consists in the development and design of an energy harvesting device to supply power to the new generation pacemakers, miniaturized leadless implants without battery placed directly in heart chambers. After analyzing different mechanical energy sources in the cardiac environment and associated energy harvesting mechanisms, a concept based on regular blood pressure variation stood out: an implant with a flexible packaging that transmits blood forces to an internal transducer. Advantages compared to traditional inertial scavengers are mainly: greater power density, adaptability to heartbeat frequency changes and miniaturization potential. Ultra-flexible 10-µm thin metal bellows have been designed, fabricated and tested. These prototypes acting as implant packaging that deforms under blood pressure actuation have validated the proposed harvesting concept. A new type of electrostatic transducer (3D multi-layer out-of-plane overlap structure with interdigitated combs) has been introduced and fully analyzed. Promising numerical results and associated fabrication processes are presented. Also, large stroke optimized piezoelectric spiral transducers including their complex electrodes patterns have been studied through a design analysis, numerical simulations, prototype fabrication and experimental testing. Apower density of 3 µJ/cm3/cycle has been experimentally achieved. With further addressed developments, the proposed device should provide enough energy to power autonomously and virtually perpetually the next generation of pacemakers.

Cette thèse concerne la récupération d'énergie vibratoire dans le but de proposer une alternative aux batteries conventionnelles pour l’alimentation de systèmes autonomes sans fil. Ceci permettrait d’améliorer leur compacité (moins d’énergie stockée), leur tenue dans des environnements sévères (forte température) et de réduire leur besoin d'entretien. Cette étude se concentre plus particulièrement sur les générateurs oscillants bistables, intéressants pour leur grande plage de fréquences utile comparée à celle offerte par les générateurs linéaires (limitée à la zone de résonance). Cette thèse se divise en quatre grandes parties. La première présente la construction du modèle mathématique permettant de prédire les différents comportements du générateur bistable (ces derniers pouvant coexister sur certaines plages de fréquences) incluant l'étude de la stabilité aux petites perturbations. Ce modèle met en évidence des comportements du générateur encore peu exploités pour la récupération d'énergie : les comportements sous-harmoniques dont la plage de fréquences permet d'agrandir la bande passante globale du générateur. Afin d’améliorer la précision du modèle, celui-ci est ensuite complété dans la deuxième partie par un critère semi-analytique : le critère de robustesse de stabilité qui caractérise la sensibilité du générateur aux perturbations extérieures (plus un comportement est robuste plus il sera facile à maintenir dans le temps). Le modèle ainsi obtenu ainsi que le système expérimentale montrent une grande plage de fréquences sur laquelle coexistent des comportements intéressants pour la récupération d’énergie (les orbites hautes) et des comportements non désirables (les orbites basses). La troisième partie de cette thèse présente donc différentes stratégies permettant de sauter des orbites basses vers les orbites hautes en jouant directement sur les paramètres du générateur. Enfin, la quatrième et dernière partie s’attarde sur l’influence du circuit d'interface AC-DC entre le générateur bistable et la charge en vue de son intégration future. / This thesis concerns vibratory energy harvesting in order to propose an alternative to conventional batteries for the power supply of autonomous wireless systems. This would improve their compactness (less stored energy), their resistance to harsh environments (high temperature) and reduce their need for maintenance. This study focuses in particular on bistable oscillating generators, which are interesting for their large useful frequency range compared to that offered by linear generators (limited to the resonance zone). This thesis is divided into four main parts. The first presents the construction of the mathematical model to predict the different behaviors of the bistable generator (these behaviors can coexist over certain frequency ranges) including the study of stability to small disturbances. This model highlights original behaviors for energy recovery: subharmonic behaviors whose frequency range allows increasing the overall generator bandwidth. In order to improve the accuracy of the model, a semi-analytical criterion is then added: the stability robustness criterion which characterizes the sensitivity of the different behaviors to external disturbances (the more robust a behavior, the easier to maintain over time). The model obtained and the experimental prototype show a wide frequency range on which the interesting behaviors (high orbits) and the undesirable behaviors (low orbits) coexist. The third part of this thesis therefore presents different strategies for jumping from low to high orbits by playing directly on the generator parameters. Finally, the fourth and last part focuses on the influence of the AC-DC interface circuit between the bistable generator and the load for future integration.

Energy harvesting is identified as an alternative solution for powering implantable biosensors. It can potentially enable the development of self-powered implants if the harvested energy is properly handled. This development implies that batteries, which impose many limitations, are replaced by miniature harvesting devices. Customized interface circuits are necessary to correct for differences in the voltage and power levels provided by harvesting devices from one side, and required by biosensor circuits from another. This thesis investigates the available harvesting sources within the human body, proposes various methods and techniques for designing power-efficient interfaces, and presents two CMOS implementations of such interfaces. Based on the investigation of suitable sources, this thesis focuses on glucose biofuel cells and thermoelectric harvesters, which provide appropriate performance in terms of power density and lifetime. In order to maximize the efficiency of the power transfer, this thesis undertakes the following steps. First, it performs a detailed analysis of all potential losses within the converter. Second, in relation to the performed analysis, it proposes a design methodology that aims to minimize the sum of losses and the power consumption of the control circuit. Finally, it presents multiple design techniques to further improve the overall efficiency. The combination of the proposed methods and techniques are validated by two highly efficient energy harvesting interfaces. The first implementation, a thermoelectric energy harvesting interface, is based on a single-inductor dual-output boost converter. The measurement results show that it achieves a peak efficiency of 86.6% at 30 μW. The second implementation combines the energy from two sources, glucose biofuel cell and thermoelectric harvester, to accomplish reliable multi-source harvesting. The measurements show that it achieves a peak efficiency of 89.5% when the combined input power is 66 μW. / Energiskörd har identifierats som en alternativ lösning för att driva inplanterbara biosensorer. Det kan potentiellt möjliggöra utveckling av själv-drivna inplanterbara biosensorer. Denna utveckling innebär att batterier, som sätter många begränsningar, ersätts av miniatyriserade energiskördsenheter. Anpassade gränssnittskretsar är nödvändiga för att korrigera för de skillnader i spänning och effektnivå som produceras av de energialstrande enheterna, och de som krävs av biosensorkretsarna. Denna avhandling undersöker de tillgängliga källorna för energiskörd i den mänskliga kroppen, föreslår olika metoder och tekniker för att utforma effektsnåla gränssnitt och presenterar två CMOS-implementeringar av sådana gränssnitt. Baserat på undersökningen av lämpliga energiskördskällor, fokuserar denna avhandling på glukosbiobränsleceller och termoelektriska energiskördare, som har lämpliga prestanda i termer av effektdensitet och livstid. För att maximera effektiviteten hos effektöverföringen innehåller denna avhandling följande steg. Först görs en detaljerad analys av alla potentiella förluster inom boost-omvandlare. Sedan föreslår denna avhandling en designmetodik som syftar till att maximera den totala effektiviteten och effektförbrukningen. Slutligen presenterar den flera designtekniker för att ytterligare förbättra den totala effektiviteten. Kombinationen av de föreslagna metoderna och teknikerna är varierade genom två högeffektiva lågeffekts energigränssnittskretsar. Den första inplementeringen är ett termoelektriskt energiskördsgränssnitt baserat på en induktor, med dubbla utgångsomvandlare. Mätresultaten visar att omvandlaren uppnår en maximal effektivitet av 86.6% vid 30 μW. Det andra genomförandet kombinerar energin från två källor, en glukosbiobränslecell och en termoskördare, för att åstadkomma en tillförlitlig multi-källas energiskördslösning. Mätresultaten visar att omvandlaren uppnår en maximal effektivitet av 89.5% när den kombinerade ineffekten är 66 μW. / <p>QC 20170508</p> / Mi-SoC

Small wind turbines, and especially urban-mounted turbines which require no dedicated pole, have garnered great public enthusiasm in recent years. This enthusiasm has fueled widespread growth among energy conservationists, and estimates predict that the power produced nationally by small wind will increase thirty-fold by 2013. Unfortunately, most of the wind resources currently available have been designed for larger, rural-mounted turbines; thus, they are not well suited for this nascent market. A consequence of this is that many potential urban small wind turbine owners over-predict their local wind resource, which is both costly and inefficient. According to a recent study published by Encraft Ltd., small wind turbines mounted to buildings far underperformed their rural pole mounted counterparts. As a proposed solution to this problem, this project introduces the concept of a Web-based Wind Assessment System (WWAS). This system combines all the necessary resources for potential urban small wind turbine customers into a single web-based tool. The system also presents the concept of a modular wind measurement system, which couples with the WWAS to provide real-time wind data measurements. The benefits of the system include its ease of use, flexibility of installation, data accessibility from any web browser, and expert advice. The WWAS prevents potential clients from investing in a system that may not be viable for their location. In addition, a small wind turbine is designed in this project, which has a unique modular mounting system, allowing the same baseline wind turbine to attach to various structures using interchangeable mounting hardware. This includes such accessible urban structures as street lights, building corners, flag poles, and building walls, among others. This design also utilizes concepts that address some of the challenges associated with mounting small wind turbines to existing urban structures. These concepts include: swept tip blades and lower RPM to reduce noise; vibration suppression using rubber shims; a netted duct to protect wildlife; and a direct-drive permanent magnet generator to ensure low starting torque. Finally, the cost of this system is calculated using off-the-shelf components, which minimize testing and certification expense. This small wind turbine system is designed to be grid-connected, has a 6 foot diameter rotor, and is rated at 1 kW. This design features a unique modular interchangeable mounting system. The cost for this complete system is estimated to be $2,050. If a users' site has an average wind speed of 14 mph (6.5 m/s), this system will generate a return on investment in 8.5 years, leaving over 10 years of profit. The profit for this system, at this sample average wind speed, yields over $4,000 during its 20-year design life, which is a two-fold return on investment. This project has implications for various stakeholders in the small wind turbine market, including designers, engineers, manufacturers, and potential customers. Equally important is its potential role in guiding our future national--even global--energy agenda.

Ultra low power wireless sensors and sensor systems are of increasing interest in a variety of applications ranging from structural health monitoring to industrial process control. Electrochemical batteries have thus far remained the primary energy sources for such systems despite the finite associated lifetimes imposed due to limitations associated with energy density. However, certain applications (such as implantable biomedical electronic devices and tire pressure sensors) require the operation of sensors and sensor systems over significant periods of time, where battery usage may be impractical and add cost due to the requirement for periodic re-charging and/or replacement. In order to address this challenge and extend the operational lifetime of wireless sensors, there has been an emerging research interest on harvesting ambient vibration energy. Vibration energy harvesting is a technology that generates electrical energy from ambient kinetic energy. Despite numerous research publications in this field over the past decade, low power density and variable ambient conditions remain as the key limitations of vibration energy harvesting. In terms of the piezoelectric transducers, the open-circuit voltage is usually low, which limits its power while extracted by a full-bridge rectifier. In terms of the interface circuits, most reported circuits are limited by the power efficiency, suitability to real-world vibration conditions and system volume due to large off-chip components required. The research reported in this thesis is focused on increasing power output of piezoelectric transducers and power extraction efficiency of interface circuits. There are five main chapters describing two new design topologies of piezoelectric transducers and three novel active interface circuits implemented with CMOS technology. In order to improve the power output of a piezoelectric transducer, a series connection configuration scheme is proposed, which splits the electrode of a harvester into multiple equal regions connected in series to inherently increase the open-circuit voltage generated by the harvester. This topology passively increases the rectified power while using a full-bridge rectifier. While most of piezoelectric transducers are designed with piezoelectric layers fully covered by electrodes, this thesis proposes a new electrode design topology, which maximizes the raw AC output power of a piezoelectric harvester by finding an optimal electrode coverage. In order to extract power from a piezoelectric harvester, three active interface circuits are proposed in this thesis. The first one improves the conventional SSHI (synchronized switch harvesting on inductor) by employing a startup circuitry to enable the system to start operating under much lower vibration excitation levels. The second one dynamically configures the connection of the two regions of a piezoelectric transducer to increase the operational range and output power under a variety of excitation levels. The third one is a novel SSH architecture which employs capacitors instead of inductors to perform synchronous voltage flip. This new architecture is named as SSHC (synchronized switch harvesting on capacitors) to distinguish from SSHI rectifiers and indicate its inductorless architecture.

Avec l'explosion de l'Internet des Objets (IoT), de nouveaux dispositifs permettant de tagguer les objets sont nécessaires afin de permettre non seulement leur identification mais aussi d'assurer des communications fiables et de nouvelles fonctionnalités comme la détection, la localisation ou la capture d'informations. Cette tendance s'appuie sur la technologie bien établie qu'est la radiofréquence par identification (RFID) et donc l'utilisation d'étiquettes (ou tags) faibles coûts et télé-alimentés. Dans ce contexte, de nombreux travaux au niveau de la couche d'application se tournent vers la mise au point de traitements logiciels complémentaires visant à produire de nouveaux types d'information. D'autres travaux visent à améliorer la couche physique avec l'objectif de miniaturiser encore le tag mais aussi de le doter de nouvelles capacités. Jusqu'à présent, il n'existe quasiment pas de travaux concernant la transmission du signal et aucun sur l'exploitation du comportement non-linéaire des puces RFID. Cette thèse vise à étudier les phénomènes non-linéaires produits lors d'une communication RFID.Dans la première partie, deux plateformes de mesure et de caractérisation spécifiques ont été développées : la première vise à observer les signaux au cours d'une communication RFID, et alors caractériser et analyser les effets liés aux phénomènes non linéaires ; la seconde permet d'effectuer différentes mesures directement sur les puces et les caractériser en termes d'impédance, production d'harmoniques et sensibilité. Ces plateformes ont permis : 1) de mettre en évidence que les fréquences harmoniques sont porteuses d'informations qui peuvent être exploitées et même offrir de nouvelles fonctionnalités ; 2) d'obtenir de nombreuses informations sur les propriétés des puces et d'en établir un modèle électrique précis ; 3) de déterminer des critères permettant d'évaluer la performance des tags dans le contexte étudié.Dans la deuxième partie, plusieurs nouveaux tags RFID ont été conçus, fabriqués, mesurés et évalués. Ces nouveaux tags fonctionnent non seulement dans la bande UHF mais aussi sont adaptés à la troisième harmonique dans la bande des microondes. Une méthodologie et des lignes directives d'aide à la conception de ce type de tags ont été établies et s'appuient sur les deux plateformes développées afin de caractériser les différents éléments. Dans un même temps, les effets liés à la fabrication ont aussi été étudiés et des études paramétriques ont permis de mettre en évidence l'effet sur les performances de la géométrie de l'antenne et du type de puce utilisée.Dans une troisième partie, les études se sont focalisées à exploiter les effets non-linéaires des dispositifs de redressement. L'idée générale est de coupler la RFID passive avec les dispositifs de transferts de puissance et de récupération d'énergie avec pour objectifs 1) de maximiser l'efficacité de conversion RF – continu 2) et d'augmenter la distance de lecture des tags passifs. Plusieurs prototypes ont été réalisés et leurs performances ont été démontrées.L'ensemble de ces travaux a mis en évidence un nouveau concept de communication RFID exploitant les non-linéarités générées par les puces RFID. Ce concept ouvre la voie à de nouvelles applications. et a fait l'objet d'une demande de brevet international. / Powered by the exploding popularity of the Internet-of-Things (IoT), the demand for tagged devices with labels capable to ensure a reliable communication with added functions beyond the identification, such as sensing, location, health-care, among others, is growing rapidly. Certainly this growing is headed by the well-established Radio Frequency Identification (RFID) technology, and the use of wireless low-cost self-powered tags, in other words passive RFID tags, is the most widespread used alternative. In the constant evolution on this field, usually new software treatments are offered at the application layer with the objective to processing data to produce some new information. Further works aimed at improving the physical layer around the tag antenna miniaturization and matching techniques. So far, little or no work had been done on the exploitation of the communication channel, and certainly none has been done on the exploitation of the non-linear behavior of RFID chips.After presenting the RFID technology and phenomena produced by Radio Frequency (RF) non-linear devices, and leaning in some nearby works on the field, the core of this thesis starts by exposing two characterization platforms for the evaluation of non-linear phenomena presented during the reader-tag communication. One is specialized in radiating measurements considering the whole tag (antenna and chip) under test. The other is specialized in conducted measurements directly over RFID chips, allowing performing different parametric studies (power dependency, impedance, harmonic production, sensitivity). The characterization results show that harmonic signals generated from the passive RFID chip carry information.By exploiting the characterization results and to verify the hypothesis of exploitation of non-linearities in RFID, i.e. the use of harmonic signals, the research is pursued by designing, fabricating, and measuring four different configurations of RFID tags. The new RFID tags operate at the fundamental frequency in the UHF band and at its $3^{rd}$ harmonic in the microwave band. Antenna design policies, fabrication details, and parametric studies on the performance of the new prototypes are presented. The parametric study takes special care in the antenna structure, kind of chip used, received power, and read range.Finally, some alternatives approaches for the exploitation of non-linear effects generated by rectifying devices are presented. Some theoretical aspects and experimental results are discussed linking the passive RFID technology to the theories of Wireless Power Transfer (WPT) and Electromagnetic Energy Harvesting (EEH). The solution takes advantage of the non-linear nature of rectifying elements in order to maximize the RF-to-DC conversion efficiency of EEH devices and increase the read range of passive RFID tags. The solution triggers on the design of a RF multi-device system. The design procedure and tests consider three non-linear phenomena: (1) the impedance power dependency, (2) the harmonic production, and (3) the rectifying dependence on the RF waveform.

Abstract The Internet of Things (IoT) is already providing solutions to various tasks related to monitoring the environment and controlling devices over wired and wireless networks. It is estimated by several well-known research facilities that the number of IoT devices will be in the order of tens of billions by 2020. This inevitably brings challenges and costs in deployment, management, and maintenance of networks. The focus of this thesis is to provide solutions that mainly help in the deployment and maintenance of various wireless IoT networks. Different applications have different requirements for a wireless link coverage. It is important to utilize suitable radio technology for a particular application in order, e.g., to maximize the lifetime of a device. A wireless body area network (WBAN) typically consists of devices that are within couple of meters from each other. The WBAN is suitable for, e.g., measuring muscle activity and transferring data to a storage for processing. The wireless link can use air as a medium, or alternatively, an induced electric field to a body can be used. In this thesis, it is shown that a location of the electrodes in the body have impact to the attenuation. Home automation IoT applications are typically implemented with mid-range wireless technologies, known as wireless personal area networks (WPAN). In order to minimize and get rid of battery change operations, a wake-up receiver could be utilized in order to improve the device’s energy efficiency. The concept is introduced and performance of the current state-of-the-art works are presented. In addition, a control loop enabling a passive device to have control over an energy source is proposed. Applications that have low bandwidth requirements can be implemented with low-power wide area networks (LPWAN). One technology – LoRaWAN – is evaluated, and it is recommended as based on the results to use it in non-critical applications. / Tiivistelmä Esineiden internet (Internet of Things, IoT) mahdollistaa jo laajan kirjon erilaisia ratkaisuja ympäristön monitorointiin ja laitteiden hallintaan hyödyntäen sekä langattomia että langallisia verkkoja. Usea hyvin tunnettu tutkimusorganisaatio on arvioinut, että vuonna 2020 IoT laitteiden määrä tulee olemaan kymmenissä miljardeissa. Se luo väistämättä haasteita laitteiden sijoittamisessa, hallinnassa ja kunnossapidossa. Tämä väitöskirja keskittyy tarjoamaan ratkaisuja, jotka voivat helpottaa langattomien IoT laitteiden sijoittamisessa ja kunnossapidossa. IoT sovellusten laaja kirjo vaatii erilaisia langattomia radioteknologioita, jotta sovellukset voitaisiin toteuttaa, muun muassa, mahdollisimman energiatehokkaasti. Langattomassa kehoverkossa (wireless body area network, WBAN) käytetään usein hyvin lyhyitä langattomia linkkejä. WBAN on soveltuva esimerkiksi lihasten aktiivisuus mittauksessa ja mittaustiedon siirtämisessä talteen varastointia ja prosessointia varten. Linkki voidaan toteuttaa käyttäen ilmaa rajapintana, tai vaihtoehtoisesti, kehoa. Tässä työssä on näytetty, että käytettäessä kehoa siirtotienä, elektrodien sijainnilla on merkitystä signaalin vaimennuksen kannalta. Kotiautomaatio IoT sovellukset ovat tyypillisesti toteutettu käyttäen langatonta likiverkkoa, jossa linkin pituus sisätiloissa on alle 30 metriä. Jotta päästäisiin eroon pariston vaihto-operaatiosta tai ainakin vähennettyä niiden määrää, herätevastaanotinta käyttämällä olisi mahdollista parantaa laitteiden energiatehokkuutta. Herätevastaanotin konsepti ja tämänhetkistä huipputasoa edustavien vastaanottimien suorituskyky ovat esitetty. Lisäksi, on ehdotettu menetelmä joka takaa energian saannin passiiviselle IoT laitteelle. IoT sovellukset jotka tyytyvät vähäiseen kaistanleveyteen voidaan toteuttaa matalatehoisella laajan alueen verkolla (low-power wide area network, LPWAN). Yhden LPWAN teknologian, nimeltään LoRaWAN, suorituskykyä on evaluoitu. Tulosten perusteella suositus on hyödyntää kyseistä teknologiaa ei-kriittisissä sovelluksissa.

Resource allocation in wireless networks is one of the most studied class of problems. Generally, these problems are formulated as utility maximization problems under relevant constraints. The challenges posed by these problems vary widely depending on the nature of the utility function under consideration. Recently, the widespread prevalence of wireless devices prompted researchers and engineers to delve into the security issues of wireless communication. As compared to the wired medium, ensuring security for the wireless medium is more challenging mainly due to the broadcast nature of the transmission. But the ongoing research on physical layer security promises robust and reliable security schemes for wireless communication. Contrary to conventional cryptographic schemes, physical layer security techniques are impregnable as the security is ensured by the inherent randomness present in the wireless medium. In this thesis, we consider several wireless scenarios and propose secrecy enhancing resource allocation schemes for them in the first few chapters. We initially address the problem of secure transmission by following the conventional approach in the secrecy literature|secrecy rate maximization. Needless to say, in these chapters, secrecy rate is the utility function and the constraints are posed by the available power budget. Then we consider a pragmatic approach where we target the signal-to-noise ratio (SNR) of participating nodes and ensure information secrecy by appropriately constraining the SNRs of those nodes. In those SNR based formulations, SNR at the destination is the utility function and we are interested in maximizing it. In the last two chapters, we study two scenarios in a non-secrecy setting. In one of them, end-to-end data rate is the utility, whereas, in the other one, two utility functions|based on revenue generated|are defined for two rational agents in a game-theoretic setting. In the second chapter, we study parallel independent Gaussian channels with imperfect channel state information (CSI) for the eavesdropper. Firstly, we evaluate the probability of zero secrecy rate in this system for (i) given instantaneous channel conditions and (ii) a Rayleigh fading scenario. Secondly, when non-zero secrecy is achievable in the low SNR regime, we aim to solve a robust power allocation problem which minimizes the outage probability at a target secrecy rate. In the third, fourth and fifth chapters, we consider scenarios where the source node transmits a message to the destination using M parallel amplify-and-forward (AF) relays in the presence of a single or multiple eavesdroppers. The third chapter addresses the problem of the maximum achievable secrecy rate for two specific network models: (a) degraded eavesdropper channel with complex channel gain and (b) scaled eavesdropper channel with real-valued channel gains. In the fourth chapter, we consider the SNR based approach and address two problems: (i) SNR maximization at the destination and (ii) Total relay power minimization. In the fifth chapter, we assume that the relay nodes are untrusted and to counter them, we deliberately introduce artificial noise in the source message. For this model, we propose and solve SNR maximization problems for the following two scenarios: (i) Total power constraint on all the relay nodes and (ii) Individual power constraints on each of the relay nodes. In the sixth chapter, we address the problem of passive eavesdroppers in multi-hop wire-less networks using the technique of friendly jamming. Assuming decode-and-forward (DF) relaying, we consider a scheduling and power allocation (PA) problem for a multiple-source multiple-sink scenario so that eavesdroppers are jammed, and source-destination throughput targets are met. When channel state information (CSI) of all the node are available, we intend to minimize the total power consumption of all the transmitting nodes. In the absence of eavesdroppers CSI, we minimize vulnerability region of the network. In chapter seven, the problem of cooperative beamforming for maximizing the achievable data rate of two-hop amplify-and-forward (AF) network (in the absence of eavesdropper(s)) is considered. Along with an individual power constraint on each of the relay nodes, we consider a weighted sum power constraint. To solve this problem, we propose a novel algorithm based on the Quadratic Eigenvalue Problem (QEP) and discuss its convergence. In chapter eight, we study a Stackelberg game between a base station and a multi-antenna power beacon for wireless energy harvesting in a multiple sensor node scenario. Assuming imperfect CSI between the sensor nodes and the power beacon, we propose a utility function that is based on throughput non-outage probability at the base station. We find the optimal strategies for the base station and the power beacon that maximize their respective utility functions.

Les systèmes de récupération d'énergie sont prometteurs pour l'auto-alimentation des dispositifs intégrés. Les matériaux pyroélectriques couplant un changement de température à un changement de polarisation électrique peuvent être utilisés pour la conversion de l'énergie thermique en énergie électrique sans nécessité de maintien de gradients thermiques qui constitue un inconvénient majeur dans les modules thermoélectriques compacts. Dans cette thèse, le PbZro.52Tio.48O3 (PZT) et le BaxSr1-xTiUO3 (x = l et x = 0.7) à fort coefficients pyroélectriques, sont choisis, élaborés en couches minces épitaxiées, caractérisés pour étudier leur potentiel de récupération d'énergie thermique. Ce travail comporte deux aspects : le premier consiste au développement et l'optimisation des conditions de croissance des hétérostructures intégrées et épitaxiées sur silicium. Le deuxième est focalisé sur l'étude des propriétés fonctionnelles (ferroélectriques, diélectriques et pyroélectriques) et à l' estimation du pouvoir de récupération d'énergie principalement des couches de PZT. Une corrélation entre ces deux aspects est ainsi présente. Un changement de la structure cristalline est montré sur les empilements intégrés sur Si, en comparaison avec des structures équivalentes réalisées sur substrat de STO. L'impact de ceci a été directement constaté sur les propriétés fonctionnelles des couches hétéroépitaxiées de PZT. Ainsi une anisotropie importante de ces propriétés a pu être mise en évidence, en complétant cette étude par des mesures dans le plan a l'aide de peignes interdigités. Ces observations ont été cohérentes avec les mesures de la diffraction des rayons X en fonction de la température. Par ailleurs, les différentes méthodes et configurations de mesures du coefficient pyroélectrique sur PZT ont permis une meilleure compréhension du phénomène et la distinction des diverses contributions existantes. La mesure statique indirecte issue de la variation de la polarisation rémanente en fonction de la température renseigne sur l'effet pyroélectrique intrinsèque (et secondaire). Cependant les mesures dynamiques du courant pyroélectrique pendant un changement de la température contiennent toutes les contributions pyroélectriques et non pyroélectriques, comme les effets extrinsèques et le courant de relaxation. Des mesures pyroélectriques dynamiques sous champ électrique, se rapprochant des conditions de cycles de récupération d'énergie thermique, ont permis de montrer que des courants de conduction apparaissaient même pour des bonnes couches de PZT diélectriques épaisses. Ces courants masquent les courants pyroélectriques et rendent l'application de générateur électrique par cycles thermodynamiques sous champ électrique rédhibitoire. Des composants passifs n'utilisant pas ou peu de champs électriques tels que des capteurs devront plutôt être envisagées. / Due to the wasted heat in ever more compact microelectronic devices, the harvesting of thermal energy has become interesting for self-powering small devices. Consequently, pyroelectric materials witch couple a change in temperature to a change in electrical polarization may be used for the conversion of the thermal energy to an electric energy without necessity of maintaining thermal gradients that is a main drawback in compact devices with thermoelectric materials. In this thesis, PbZro.52Tio.48O3 (PZT) and BaxSr1-xTiUO3 (x = l and x = 0.7), with high pyroelectric coefficients are chosen, elaborated in thin epitaxial layers, characterized structurally and electrically to study their potential for thermal energy harvesting. This work has two aspects: the first consists in the development and optimization of the growth conditions of epitaxial heterostructures integrated on Si. The second one focuses on the study of the functional properties ( ferroelectric, dielectric and pyroelectric) and the estimation of the energy harvesting efficiency mainly of PZT layers. A correlation between these two aspects is then done. A change in the crystal structure is shown on the Si-integrated stacks in comparison with equivalent structures grown on STO substrate. This structural behavior impacts directly the functional properties of the heteroepitaxial layers of PZT. Th us, an important anisotropy of these properties was demonstrated and completed by a study of the in plane properties using measurements by interdigital capacitors. These observations were consistent with measurements of X - ray diffraction as a function of temperature. Otherwise, different methods and configurations of pyroelectric coefficient measurements on PZT have allowed a better understanding of the phenomenon and the distinction of the various existing contributions. The indirect static measurement resulting from the variation of the remnant polarization as a function of the temperature gives the intrinsic (and secondary) pyroelectric contributions. However, the dynamic measurements of the pyroelectric current during a change of the temperature contain all the pyroelectric and non-pyroelectric contributions, such as the extrinsic effects and the relaxation current . Dynamic pyroelectric measurements under an electric field are near to the conditions of thermal energy harvesting cycles. Conduction currents appeared, even for good layers of thick dielectric PZT, and mask the pyroelectric currents. This makes the application of electric generator by thermodynamic cycles under electric field prohibitive. Passive components using low or no electrical field such as sensors should be considered.

Inductive power transfer (IPT) systems with tolerance to the lateral misalignment are advantageous for enhancing the transmitted power, usability and security of the system. In this thesis, a misalignment tolerant multi-coil design is proposed to supply stationary and dynamic battery-free wireless devices. A compact architecture composed of individually switchable 3 layers of printed coils arranged with overlap for excellent surface coverage. A hybrid architecture based on three compact AC supply modules reduces the supply circuit complexity on the sending Seite 2 von 4side. It detects the position of the receiver coil quickly, controls the activation of the transmitting coils and estimates the next receiver position. The proposed architecture reduces the circuit footprint by a factor of 62% compared to common architectures. A transmitter coil activation strategy is proposed based on the detection of the transmitting coils voltage and communication between sending side and receiving side to detect devices to supply nature and position and to differentiate them from other conductive objects in the sending area to the supplying security. The experimental results prove that the proposed architecture has a good performance for different trajectories when the device speed does not exceed 15 mm/s. Besides, the maximum detection time for the initial device position is about 1.6 s. The maximal time interval to check the transmitter coils is around 0.7 s.:1. INTRODUCTION 2. THEORETICAL BACKGROUND 3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS 4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM 5. MULTI-COIL ACTIVATION PROCEDURE 6. EXPERIMENTAL INVESTIGATIONS 7. CONCLUSION AND OUTLOOK / Induktive Energieübertragungssysteme (IPT) mit Toleranz gegenüber seitlichem Versatz sind vorteilhaft, um die übertragene Leistung, die Nutzbarkeit und die Sicherheit des Systems zu verbessern. In dieser Arbeit wird ein versatztolerantes Multispulen-Design vorgeschlagen, um stationäre und dynamische batterielose drahtlose Geräte zu versorgen. Die kompakte Architektur besteht aus 3 einzeln schaltbaren Schichten gedruckter Spulen, die überlappend angeordnet sind, um eine hervorragende Oberflächenabdeckung zu gewährleisten. Eine hybride Architektur, die auf drei kompakten AC-Versorgungsmodulen basiert, reduziert die Komplexität der Versorgungsschaltung auf der Senderseite. Sie erkennt die Position der Empfängerspule schnell, steuert die Aktivierung der Sendespulen und schätzt die nächste Empfängerposition. Die vorgeschlagene Architektur reduziert den Platzbedarf der Schaltung um einen Faktor von 62 % im Vergleich zu herkömmlichen Architekturen. Es wird eine Aktivierungsstrategie für die Sendespulen vorgeschlagen, die auf der Erkennung der Spannung der Sendespulen und der Kommunikation zwischen Sende- und Empfangsseite basiert, um die Art und Position der zu versorgenden Geräte zu erkennen und sie von anderen leitfähigen Objekten im Sendebereich zu unterscheiden. Die experimentellen Ergebnisse zeigen, dass die vorgeschlagene Architektur eine gute Leistung für verschiedene Trajektorien hat, wenn die Geschwindigkeit der Geräte 15 mm/s nicht überschreitet. Außerdem beträgt die maximale Erkennungszeit für die anfängliche Geräteposition etwa 1,6 s. Das maximale Zeitintervall für die Überprüfung der Senderspulen beträgt etwa 0,7 s.:1. INTRODUCTION 2. THEORETICAL BACKGROUND 3. STATE OF THE ART OF MULTI-COIL IPT SYSTEMS 4. NOVEL DESIGN OF A MULTI-COIL IPT SYSTEM 5. MULTI-COIL ACTIVATION PROCEDURE 6. EXPERIMENTAL INVESTIGATIONS 7. CONCLUSION AND OUTLOOK