Mixed-source charger-supply CMOS IC

The proposed research objective is to develop, test, and evaluate a mixer and charger-supply CMOS IC that derives and mixes energy and power from mixed sources to accurately supply a miniaturized system. Since the energy-dense source stores more energy than the power-dense source while the latter supplies more power than the former, the proposed research aims to develop an IC that automatically selects how much and from which source to draw power to maximize lifetime per unit volume. Today, the state of the art lacks the intelligence and capability to select the most appropriate source from which to extract power to supply the time-varying needs of a small system. As such, the underlying objective and benefit of this research is to reduce the size of a complete electronic system so that wireless sensors and biomedical implants, for example, as a whole, perform well, operate for extended periods, and integrate into tiny spaces.Ph.D

Wireless Telemetry System for Implantable Sensors

Advanced testing of medical treatments involves experimentation on small laboratory animals, such as genetically modified mice. These subjects are used to help researchers develop medication and cures for humans. To understand the effects of the treatments, innovative telemetry systems are developed, that enable remote real-time cardiac monitoring. The latest research in the field of cardiac monitoring has revealed two major limitations with wireless implantable systems: a) the current size of implantable electronics limits the physical size of the system to larger subjects; and b) the systems only interface with one sensor type (e.g., pressure sensor only). This research focuses on the design of a wireless telemetry system architecture, intended to retrieve blood pressure and volume data. A physical prototype is created that is 2.475 cm3 and weights 4.01 g. This thesis will enable a path towards miniaturization, leading to the incorporation of a wireless system into small laboratory animals

CMOS indoor light energy harvesting system for wireless sensing applications

Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de ComputadoresThis research thesis presents a micro-power light energy harvesting system for indoor environments. Light energy is collected by amorphous silicon photovoltaic (a-Si:H PV) cells, processed by a switched-capacitor (SC) voltage doubler circuit with maximum power point tracking (MPPT), and finally stored in a large capacitor. The MPPT Fractional Open Circuit Voltage (VOC) technique is implemented by an asynchronous state machine (ASM) that creates and, dynamically, adjusts the clock frequency of the step-up SC circuit, matching the input impedance of the SC circuit to the maximum power point (MPP) condition of the PV cells. The ASM has a separate local power supply to make it robust against load variations. In order to reduce the area occupied by the SC circuit, while maintaining an acceptable efficiency value, the SC circuit uses MOSFET capacitors with a charge reusing scheme for the bottom plate parasitic capacitors. The circuit occupies an area of 0.31 mm2 in a 130 nm CMOS technology. The system was designed in order to work under realistic indoor light intensities. Experimental results show that the proposed system, using PV cells with an area of 14 cm2, is capable of starting-up from a 0 V condition, with an irradiance of only 0.32 W/m2. After starting-up, the system requires an irradiance of only 0.18 W/m2 (18 mW/cm2) to remain in operation. The ASM circuit can operate correctly using a local power supply voltage of 453 mV, dissipating only 0.085 mW. These values are, to the best of the authors’ knowledge, the lowest reported in the literature. The maximum efficiency of the SC converter is 70.3% for an input power of 48 mW, which is comparable with reported values from circuits operating at similar power levels.Portuguese Foundation for Science and Technology (FCT/MCTES), under project PEst-OE/EEI/UI0066/2011, and to the CTS multiannual funding, through the PIDDAC Program funds. I am also very grateful for the grant SFRH/PROTEC/67683/2010, financially supported by the IPL – Instituto Politécnico de Lisboa

Digital signal processing techniques for peak-to-average power ratio mitigation in MIMO–OFDM systems

The focus of this thesis is to mitigate the very large peak-to-average transmit power ratios (PAPRs) inherent to conventional orthogonal frequency division multiplexing (OFDM) systems, particularly in the context of transmission over multi-input multi-output (MIMO) wireless broadband channels. This problem is important as a large PAPR generally needs an expensive radio frequency (RF) power amplifier at the transmitter due to the requirement for linear operation over a wide amplitude range and such a cost would be compounded when multiple transmit antennas are used. Advanced signal processing techniques which can reduce PAPR whilst retain the integrity of digital transmission therefore have considerable potential for application in emergent MIMO–OFDM wireless systems and form the technical contributions of this study. [Continues.

Survey of FPGA applications in the period 2000 – 2015 (Technical Report)

Romoth J, Porrmann M, Rückert U. Survey of FPGA applications in the period 2000 – 2015 (Technical Report).; 2017.Since their introduction, FPGAs can be seen in more and more different fields of applications. The key advantage is the combination of software-like flexibility with the performance otherwise common to hardware. Nevertheless, every application field introduces special requirements to the used computational architecture. This paper provides an overview of the different topics FPGAs have been used for in the last 15 years of research and why they have been chosen over other processing units like e.g. CPUs

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Structures et contrôle d'amplificateurs de puissance et de convertisseurs statiques d'énergie électrique en vue de leur enfouissement

Ce manuscrit d’HDR discute de structure et de contrôle de convertisseurs et d’amplificateurs, dans les gammes de tension de quelques volts et de puissance inférieure au watt, en vue de leurs enfouissements au sein de circuits intégrés. Enfouis, car au-delà d’être intégrés, ils sont distribués au sein de chaque fonction, et finalement dissimulés d’un point de vue système. Cette approche répond aux multiples verrous limitant l’autonomie, augmentant le volume d’un système électronique et réduisant leurs fiabilités.Je situe principalement mes travaux par rapport à l’état de l’art sur les méthodologies de simulation et d’analyse de structure, et de leurs contrôles, complétées par des propositions de circuit et leurs implémentations à des fins de validations expérimentales. L’exploration des trois grandes familles de convertisseurs, capacitif, inductif et résonant, et leurs hybridations par connexion série ou parallèle, ont permis de dégager des tendances de miniaturisation, des lois en vue de la prédiction de certaines de leurs performances, notamment le rendement énergétique. Cette étude structurelle est également un déclencheur et un aiguilleur d’évolution des technologies. Par la suite, différents types de contrôle, pour fournir une alimentation stable ou variable rapidement, sont analysés tels que le contrôle analogique et numérique à fréquence fixe ou variable. La contribution est majoritairement orientée vers la proposition de boucles d’asservissement originales, plutôt analogiques, intimement liées au convertisseur. Ces apports à multiples facettes sont autant de clefs vers l’enfouissement des convertisseurs.Je me suis attaché à décrire mes apports repris dans une quinzaine d’articles internationaux, une trentaine de conférences internationales et une dizaine de brevets à ce jour. Je reste également actif dans la mission d’enseignement et contribue à la formation par la recherche dans ce domaine, peu couvert par les formations initiales.Au niveau des perspectives, il paraît nécessaire de continuer à explorer de nouvelles structures ou à revisiter certaines, à la lumière des technologies émergentes sur une échelle de puissance élargie couvrant également le milliwatt. Dans un esprit de décloisonnement et pour créer de nouvelles filières, je souhaiterais porter de nouveaux projets en collaboration avec d’autres chercheurs sur l’analyse du codage logique et les convertisseurs à transduction multi domaines. Enfin, il est nécessaire de penser aux répercussions de la recherche sur la société et les orienter en fonction d’une réflexion globale