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Power consumption and battery life are of critical importance for medical implant devices. For this reason, devices for Wireless Body Area Network (WBAN) applications must consume very little power. To save power, it is desirable to turn off or put to sleep a device when not in use. However, a transceiver, which is the most power hungry block of a wireless sensor node, needs to listen for the incoming signal continuously. An alternative scheme, is to listen for the incoming signal at a predetermined internal, which saves power at the cost of increased latency. Another and more sophisticated scheme is to provide a wake-up receiver, which listens for the incoming signal continuously, and upon detection of an incoming signal, it wakes the primary transceiver up. A wake-up receiver is typically simple and dissipates little power to make the scheme useful. This thesis proposes a low-power wake-up receiver, which listens for a wake-up signal, identifies the target node, and wakes up the primary receiver only when that specific node is called upon. When a wake up signal is transmitted to all of the nodes on a network, our wake-up receiver allows all the nodes on a network except the targeted node to remain asleep to save power. Several wake-up receiver topologies have been proposed. This work uses a passive Cockcroft-Walton multiplier circuit as an RF envelope detector followed by a simple detector circuit. A novel serial code detector is then used to decode the pulse width modulated input signal to wake-up the designated node. A passive RF front end and simple decoding circuit reduce power consumption substantially at the cost of low sensitivity. The sensitivity of the wake-up receiver can be improved though the addition of an RF amplifier, but at the cost of increased power consumption. / Master of Science

Nous avons étudié des magmas ferrifères silicatés magnésiens à la pression du manteau terrestre en utilisant la dynamique moléculaire (First Principles Molecular Dynamics). Les résultats de l’équation d’état que nous avons obtenus à partir de nos simulations ont été utilisés pour créer un modèle chimique et minéralogique pour les zones de très basse vitesse sismique (ULVZ, anomalies régionales dans le manteau proche de la limite noyau-manteau). De plus, nous avons étudié le comportement du Ni, du Co et du Fe dans ces magmas et établi la dépendance du spin en fonction de la concentration, de la pression, de la température et du degré de polymérisation du magma silicaté. Nous avons montré qu’une baisse du spin moyen peut être corrélée au changement de pente (kink) observé précédemment pour les coefficients de partage du Ni et du Co. Nous avons analysé la structure du magma pour toutes les compositions étudiées en fonction de la pression. Nos résultats donnent un nouvel aperçu de la coordination des éléments majeurs et traces dans les magmas silicatés de différents degrés de polymérisation. Nous interprétons l’anomalie de coordination Ni-O en fonction de la pression comme un changement d’état de spin. L’effet de la polymérisation du magma silicaté sur les coefficients de partage du Co, du Ni et du W entre le métal et le magma silicaté a été étudié par expériences multi-enclumes en conditions isobares et isothermes. Nous avons réalisé des simulations FPMD de magmas à des degrés de polymérisation similaires aux expériences afin d’expliquer le caractère de plus en plus lithophile du W lorsque le degré de polymérisation du magma silicaté diminue. Nous proposons une explication structurale pour expliquer l’affinité décroissante apparente du W dans les magmas silicatés dépolymérisés. / We explore Fe-bearing Mg-silicate melts through the pressure regime of the Earth’s mantle using First Principles Molecular Dynamics (FPMD). The equation of state results we obtained from our simulations are used to create a chemical and mineralogical model for Ultra-Low Velocity Zones (anomalous region on the mantle side of the core-mantle boundary). Furthermore we study the behaviour of Ni, Co, and Fe in these melts, and asses their spin-crossover dependencies on their concentration, pressure, temperature, and the degree of polymerization of the silicate melts. We show that a decrease in the average spin can be correlated with the previously observed kink in the partitioning coefficient of Ni and Co. We investigate the melt structure of all the compositions studied as a function of pressure. Our results provide new insight into the coordination of major and trace elements in silicate melts with different degrees of polymerization. We interpret the anomalous Ni-O coordination trend with pressure as the result of the spin state change. The effect of silicate melt polymerization on the partitioning of Co, Ni, and W between a metal and silicate melt, is investigated at isobaric and isothermic conditions using multi-anvil experiments. We have performed FPMD simulations of melts with similar degrees of polymerization as the experiments in order to explain the increasing lithophile character of W with the decrease in polymerization of the silicate melt. We propose a structural explanation for tungsten’s apparent increased affinity for depolymerized silicate melts.

Noise in electronic circuits can sometimes cause problems. It is especially problematic in for example high sensitive sensors and high end audio and video equipment. In audio and video equipment the noise will make its way into the sound and picture reducing the overall quality. Sensors that are constructed to sense extremely small changes can only pick up changes larger than the noise floor of the circuit. By lowering the noise, sensors can achieve higher accuracy.  This thesis presents an ultra low noise solution of the biasing circuitry to the bolometer used in one of FLIR Systems high end cameras. The bolometer uses different adjustable direct current voltage sources and is extremely sensitive to noise. The purpose is to improve the picture quality and the thermal measurement resolution. A prototype circuit was constructed and in the end of the thesis a final circuit with successful result will be presented.

An alternative indirect integration regime of porous low-k materials was investigated. Based on a single Damascene structure the intra level dielectric SiO2 or damaged ULK was removed by using HF:H2O solutions to create free standing metal lines. The free spaces between the metal lines were refilled with a spin-on process of a low-k material. The persistence of barrier materials and copper against HF solutions, the gap fill behavior of the used spin on glass on different structure sizes and the main challenges which have to solve in the future are shown in this study.

Energy harvesting is becoming increasingly important in low-power applications where energy from the environment is used to power the system alone, or to supplement a battery. For example, pulse oximeter sensors inside helmets of road racing cyclists are powered by the sun. These sensors have become smaller and more practical without the limitation of a finite energy supply. Harvested energy from an energy transducer (solar, piezoelectric, etc.) must be maximized to ensure these devices can survive periods where environmental energy is scarce. The conversion process from the transducer to usable power for the device is not perfectly efficient. Specifically, the output voltage of a solar cell is a function of the light intensity, and by extension the load it powers. A small perturbation of the light source quickly diminishes the available power. The wasted power reduces the energy available for the application, and can be improved using an approach called maximum power point tracking (MPPT). This technique maximizes harvesting efficiency by dynamically impedance matching the transducer to its load. This report introduces the Maximum Efficient Solar Harvester (MESH), an MPPT algorithm tuned for a specific Wireless Sensor Network (WSN) application. MESH specifically controls the operation of the DC-DC converter in a solar power management unit (PMU). The control is done by monitoring the available light and feeding that information to choose the optimal operating point DC-DC converter. This operating point has a direct dependency on the overall efficiency of the system. For MESH to be practical, the cost and power overhead of adding this functionality must be assessed. Empirical results indicate that MESH improves the maximum efficiency of the popular Texas Instruments (TI) RF2500-SEH WSN platform by an average of 20%, which far exceeds the power overhead it incurs. The cost is also found to be minimal, as WSN platforms already include a large portion of the hardware required to implement MESH. The report was done in collaboration with Stephen Kobdish. It covers the software implementation and MESH architecture definition; Kobdish's companion report focuses on hardware components and the bench automation environment. / text

Neste trabalho, foi investigado o comportamento tribológico dos pares cerâmicos aluminanitreto de silício no deslizamento em água e em uma suspensão de sílica coloidal em água (hidrosol). O objetivo foi verificar a possibilidade de atingir um coeficiente de atrito da ordem de unidades de milésimos, aqui chamado de ultra-baixo coeficiente de atrito (UBCA), verificar se a mudança do meio, de água para hidrosol, diminui o running-in do coeficiente de atrito, e verificar o efeito da variação da rugosidade inicial da alumina no comportamento do atrito. Os ensaios foram realizados na configuração de teste esferasobre- disco, no qual a esfera foi de nitreto de silício e o disco de alumina, sob carga normal de 54 N e velocidade de 1 m/s. A água utilizada nos ensaios foi destilada e deionizada, e a sílica coloidal amorfa, hidrofílica, sem porosidade e de tamanho médio de partícula de 12 nm foi a Aerosil® 200, e o hidrosol foi preparado com pH 8,5 num eletrólito de NaCl de 1 mM. A esfera de nitreto de silício, adquirida comercialmente, e a alumina, sinterizada em laboratório, foram caracterizadas quanto a densidade, as fases foram determinadas por difração de raios X, microscopia eletrônica de varedura (MEV) observada em amostras ceramográficas atacadas. Algumas propriedades mecânicas como dureza, módulo de elasticidade e tenacidade à fratura foram determinadas. Duas condições de rugosidade dos discos de alumina foram utilizadas nos ensaios tribológicos, 350 nm e 10 nm RMS. Em todos os ensaios, em água, em hidrosol e independentemente da rugosidade inicial do disco o coeficiente de atrito no regime permanente apresentou pequena dispersão de valores de 0,002 a 0,006, e não foi possível estabelecer diferença entre elas. A menor rugosidade do disco de alumina acarretou menor desgaste e menor período de running-in de coeficiente de atrito, tanto em água quanto em hidrosol. Os ensaios em meio de hidrosol acarretaram menor desgaste das cerâmicas e apresentaram menor running-in de coeficiente de atrito, comparados aos ensaios com água. O disco de alumina apresentou menor desgaste do que a esfera de nitreto de silício, em todas as condições estudadas. Com a análise das perdas volumétricas, da rugosidade final das superfícies desgastadas, das curvas de coeficiente de atrito e das espessuras mínimas de filme lubrificante, calculadas com uso de modelo da literatura, foi possível relacionar a diminuição do desgaste e do running-in de coeficiente de atrito em meio de hidrosol, com a presença da sílica na superfície ou próxima dela. / In this work, the tribological behavior of the alumina-silicon nitride couple was investigated under water and hydrosol (colloidal silica suspensions in water) lubricated sliding. The purposes were to study how an ultra-low friction coefficient can be achieved and to analyze the effects of the environment, lubricant and alumina roughness changes on the friction behavior. Ball-on-disk tests with a normal load of 54 N and a sliding speed of 1 m/s were carried out, using a silicon nitride ball and an alumina disk. The water used as lubricant was distilled and deionized. The silica was amorphous colloidal and hydrophilic, without porous and with a 12 nm medium particle diameter, commercially named Aerosil ® 200. The hydrosol was obtained with a pH value of 8,5 and a 1mM NaCl electrolyte. To estimate the minimum film thickness, formed during the lubricated sliding tests, a theory model was used. The commercial silicon nitride balls and the alumina disks, which were conformed and sintered in laboratory, were characterized by density, X-ray diffraction and scanning electron microscopy measurements. The mechanical properties such as hardness, Young modulus and fracture toughness were determined. The friction coefficient values obtained in the steady state regime showed low standard deviations (0,002 to 0,006) under all conditions. A shorter period of running-in was observed with the lower disk roughness, both in water and hydrosol lubrication. The hydrosol lubricated sliding produced a lower wear and friction running-in comparing with the tests under water lubrication. The alumina disk always showed lower wear than the silicon nitride ball. The volume loss, friction coefficients, worn surfaces roughness and minimum film thickness results suggest that the wear and friction coefficient running-in decrease was caused by the presence of silica on the sliding surfaces or on the near surface regions.

Message Authentication Codes (MACs) are valuable tools for ensuring the integrity of messages. MACs may be built around a keyed hash function. Our main motivation was to prove that universal hash functions can be employed as underlying primitives of MACs in order to provide provable security in ultra-low-power applications such as the next generation self-powered sensor networks. The idea of using a universal hash function (NH) was explored in the construction of UMAC. This work presents three variations on NH, namely PH, PR and WH. The first hash function we propose, PH, produces a hash of length 2w and is shown to be 2^(-w)-almost universal. The other two hash functions, i.e. PR and WH, reach optimality and are proven to be universal hash functions with half the hash length of w. In addition, these schemes are simple enough to allow for efficient constructions. To the best of our knowledge the proposed hash functions are the first ones specifically designed for low-power hardware implementations. We achieve drastic power savings of up to 59% and speedup of up to 7.4 times over NH. Note that the speed improvement and the power reduction are accomplished simultaneously. Moreover, we show how the technique of multi- hashing and the Toeplitz approach can be combined to reduce the power and energy consumption even further while maintaining the same security level with a very slight increase in the amount of key material. At low frequencies the power and energy reductions are achieved simultaneously while keeping the hashing time constant. We develope formulae for estimation of leakage and dynamic power consumptions as well as energy consumption based on the frequency and the Toeplitz parameter t. We introduce a powerful method for scaling WH according to specific energy and power consumption requirements. This enables us to optimize the hash function implementation for use in ultra-low-power applications such as "Smart Dust" motes, RFIDs, and Piconet nodes. Our simulation results indicate that the implementation of WH-16 consumes only 2.95 ìW 500 kHz. It can therefore be integrated into a self- powered device. By virtue of their security and implementation features mentioned above, we believe that the proposed universal hash functions fill an important gap in cryptographic hardware applications.

<p>This master thesis deals with the study of ultra low power Low Noise Amplifier (LNA) for use inmedical implant device. Usually, low power consumption is required for a long battery lifetime andlonger operation. The target technology is 90nm CMOS process.First basic principle of LNA is discussed. Then based on a literature review of LNA design, theproposed LNA is presented in sub-threshold region which reduce power consumption through scalingthe supply voltage and through scaling current.The circuit implementation and simulations is presented to testify the performance of LNA .Besides thepower consumption simulated under the typical supply voltage (1V), it is also measured under someother low supply voltages (down to 0.5V) to investigate the minimum power consumption and theminimum noise figure. Evaluation results show that at a supply voltage of 1V the LNA performs a totalpower consumption of 20mW and a noise of 1dB. Proper performance is achieved with a current ofdown to 200uA and supply voltage of down to 0.45V, and a total power consumption of 200uW</p>

This master thesis deals with the study of ultra low power Low Noise Amplifier (LNA) for use inmedical implant device. Usually, low power consumption is required for a long battery lifetime andlonger operation. The target technology is 90nm CMOS process.First basic principle of LNA is discussed. Then based on a literature review of LNA design, theproposed LNA is presented in sub-threshold region which reduce power consumption through scalingthe supply voltage and through scaling current.The circuit implementation and simulations is presented to testify the performance of LNA .Besides thepower consumption simulated under the typical supply voltage (1V), it is also measured under someother low supply voltages (down to 0.5V) to investigate the minimum power consumption and theminimum noise figure. Evaluation results show that at a supply voltage of 1V the LNA performs a totalpower consumption of 20mW and a noise of 1dB. Proper performance is achieved with a current ofdown to 200uA and supply voltage of down to 0.45V, and a total power consumption of 200uW