Circuits Techniques for Wireless Sensing Systems in High-Temperature Environments

RÉSUMÉ Dans ce projet, nous proposons de nouvelles techniques d’intégration basées sur la technologie de nitrure de gallium (GaN). Ces techniques permettent de mettre en œuvre un système de transmission de données sans fil entièrement intégré dédié aux capteurs de surveillance pour des applications d'environnement hostile. Le travail nécessite de trouver une technologie capable de résister à l'environnement sévère, principalement à haute température, et de permettre un niveau d'intégration élevé. Le système réalisé serait le premier dispositif de transmission de données basé sur la technologie GaN. En plus de supporter les conditions de haute température (HT) dépassant 600 oC, le système de transmission sans fil attendu devrait fonctionner à travers une barrière métallique séparant le module émetteur du récepteur. Une revue de la littérature sur les applications en environnements hostiles ainsi que sur l'électronique correspondante a été réalisée pour sélectionner la technologie AlGaN/GaN HEMT (transistor à haute mobilité d'électrons) comme une technologie appropriée. Le kit de conception GaN500, fourni par le Conseil national de recherches du Canada (CNRC), a été adopté pour concevoir et mettre en œuvre le système proposé. Cette technologie a été initialement introduite pour desservir les applications radiofréquences (RF) et micro-ondes. Par conséquent, elle n'avait pas été validée pour concevoir et fabriquer des circuits intégrés analogiques et numériques complexes et son utilisation à des températures extrêmes n’était pas validée. Nous avons donc caractérisé à haute température des dispositifs fabriqués en GaN500 et des éléments passifs intégrés correspondants ont été réalisés. Ces composants ont été testés sur la plage de température comprise entre 25 et 600 oC dans cette thèse. Les résultats de caractérisation ont été utilisés pour extraire les modèles HT des HEMT intégrés et des éléments passifs à utiliser dans les simulations. En outre, plusieurs composants intégrés basés sur la technologie GaN500, notamment des NOT, NOR, NAND, XOR, XNOR, registres, éléments de délais et oscillateurs ont été mis en œuvre et testés en HT. Des circuits analogiques à base de GaN500, comprenant un amplificateur de tension, un comparateur, un redresseur simple alternance, un redresseur double alternance, une pompe de charge et une référence de tension ont également été mis en œuvre et testés en HT. Le système de transmission de données mis en œuvre se compose d'un module de modulation situé dans la partie émettrice et d'un module de démodulation situé dans la partie réceptrice.----------ABSTRACT In this project, we propose new integrated-circuit design techniques based on the Gallium Nitride (GaN) technology to implement a fully-integrated data transmission system dedicated to wireless sensing in harsh environment applications. The goal in this thesis is to find a proper technology able to withstand harsh-environments (HEs), mainly characterized by high temperatures, and to allow a high-integration level. The reported design is the first data transmission system based on GaN technology. In addition to high temperature (HT) environment exceeding 600 oC, the expected wireless transmission systems may need to operate through metallic barriers separating the transmitting from the receiving modules. A wide literature review on the HE applications and corresponding electronics has been done to select the AlGaN/GaN HEMT (high-electron-mobility transistor) technology. The GaN500 design kit, provided by National Research Council of Canada (NRC), was adopted to design and implement the proposed system. This technology was initially provided to serve radio frequency (RF) and microwave circuits and applications. Consequently, it was not validated to implement complex integrated systems and to withstand extreme temperatures. Therefore, the high-temperature characterization of fabricated GaN500 devices and corresponding integrated passive elements was performed over the temperature range 25-600 oC in this thesis. The characterization results were used to extract HT models of the integrated HEMTs and passive elements to be used in simulations. Also, several GaN500-based digital circuits including NOT, NOR, NAND, XOR, XNOR, register, Delay and Ring oscillator were implemented and tested at HT. GaN500-based Analog circuits including front-end amplifier, comparator, half-bridge rectifier, full-bridge rectifier, charge pump and voltage reference were implemented and tested at HT as well. The implemented data transmission system consists of a modulation module located in the transmitting part and a demodulation block located in the receiving part. The proposed modulation system is based on the delta-sigma modulation technique and composed of a front-end amplifier, a comparator, a register, a charge pump and a ring oscillator. The output stage of the transmitter is intended to perform the load-shift-keying (LSK) modulation required to accomplish the data transmission through the dedicated inductive link. At the receiver level, three demodulation topologies were proposed to acquire the delivered LSK-modulated signals

Advanced photon counting applications with superconducting detectors

Superconducting nanowire single photon detectors (SNSPDs) have emerged as mature detection technology that offers superior performance relative to competing infrared photon counting technologies. SNSPDs have the potential to revolutionize a range of advanced infrared photon counting applications, from quantum information science to remote sensing. The scale up to large area SNSPD arrays or cameras consisting of hundreds or thousands of pixels is limited by efficient readout schemes. This thesis gives a full overview of current SNSPD technology, describing design, fabrication, testing and applications. Prototype 4-pixel SNSPD arrays (30 x 30 µm2 and 60 x 60 µm2) were fabricated, tested and time-division multiplexed via a power combiner. In addition, a photon-number resolved code-division multiplexed 4-pixel array was simulated. Finally, a 100 m calibration-free distributed fibre temperature testbed, based on Raman backscattered photons detected by a single pixel fibre-coupled SNSPD housed in a Gifford McMahon cryostat was experimentally demonstrated with a spatial resolution of approximately 83 cm. At present, it is the longest range distributed thermometer based on SNSPD sensing

High-efficiency voltage source converters with silicon super-junction MOSFETs

High-efficiency power converters have the benefits of minimising energy consumption, reducing costs, and realising high power densities. The silicon super-junction (SJ) MOSFET is an attractive device for high-efficiency applications. However, its highly non-linear output capacitance and the reverse recovery properties of its intrinsic diode must be addressed when used in voltage source converters (VSCs). The research in this thesis aims at addressing these two problems and realising high efficiency. Initially, state-of-art techniques in the literature are reviewed. In order to develop a solution with simple hardware, no major auxiliary magnetic components, and no onerous timing requirements, a dual-mode switching technique is proposed. The technique is demonstrated using a SJ MOSFET based bridge-leg circuit. The hardware performance is then experimentally investigated with different power semiconductor device permutations. The transition conditions between the two switching modes do not have to be tightly set in order to maintain a high efficiency. The dual-mode switching technique is then further investigated with a current transformer (CT) arrangement embedded in the MOSFET’s gate driver circuit in order to control the profile of the MOSFET’s incoming drain current at turn on. The dual-mode switching technique, with or without a CT scheme, is shown to achieve high efficiency with minimal additional hardware.High-efficiency power converters have the benefits of minimising energy consumption, reducing costs, and realising high power densities. The silicon super-junction (SJ) MOSFET is an attractive device for high-efficiency applications. However, its highly non-linear output capacitance and the reverse recovery properties of its intrinsic diode must be addressed when used in voltage source converters (VSCs). The research in this thesis aims at addressing these two problems and realising high efficiency. Initially, state-of-art techniques in the literature are reviewed. In order to develop a solution with simple hardware, no major auxiliary magnetic components, and no onerous timing requirements, a dual-mode switching technique is proposed. The technique is demonstrated using a SJ MOSFET based bridge-leg circuit. The hardware performance is then experimentally investigated with different power semiconductor device permutations. The transition conditions between the two switching modes do not have to be tightly set in order to maintain a high efficiency. The dual-mode switching technique is then further investigated with a current transformer (CT) arrangement embedded in the MOSFET’s gate driver circuit in order to control the profile of the MOSFET’s incoming drain current at turn on. The dual-mode switching technique, with or without a CT scheme, is shown to achieve high efficiency with minimal additional hardware

1996 Laboratory directed research and development annual report

This report summarizes progress from the Laboratory Directed Research and Development (LDRD) program during fiscal year 1996. In addition to a programmatic and financial overview, the report includes progress reports from 259 individual R&D projects in seventeen categories. The general areas of research include: engineered processes and materials; computational and information sciences; microelectronics and photonics; engineering sciences; pulsed power; advanced manufacturing technologies; biomedical engineering; energy and environmental science and technology; advanced information technologies; counterproliferation; advanced transportation; national security technology; electronics technologies; idea exploration and exploitation; production; and science at the interfaces - engineering with atoms

Políticas de Copyright de Publicações Científicas em Repositórios Institucionais: O Caso do INESC TEC

A progressiva transformação das práticas científicas, impulsionada pelo desenvolvimento das novas Tecnologias de Informação e Comunicação (TIC), têm possibilitado aumentar o acesso à informação, caminhando gradualmente para uma abertura do ciclo de pesquisa. Isto permitirá resolver a longo prazo uma adversidade que se tem colocado aos investigadores, que passa pela existência de barreiras que limitam as condições de acesso, sejam estas geográficas ou financeiras. Apesar da produção científica ser dominada, maioritariamente, por grandes editoras comerciais, estando sujeita às regras por estas impostas, o Movimento do Acesso Aberto cuja primeira declaração pública, a Declaração de Budapeste (BOAI), é de 2002, vem propor alterações significativas que beneficiam os autores e os leitores. Este Movimento vem a ganhar importância em Portugal desde 2003, com a constituição do primeiro repositório institucional a nível nacional. Os repositórios institucionais surgiram como uma ferramenta de divulgação da produção científica de uma instituição, com o intuito de permitir abrir aos resultados da investigação, quer antes da publicação e do próprio processo de arbitragem (preprint), quer depois (postprint), e, consequentemente, aumentar a visibilidade do trabalho desenvolvido por um investigador e a respetiva instituição. O estudo apresentado, que passou por uma análise das políticas de copyright das publicações científicas mais relevantes do INESC TEC, permitiu não só perceber que as editoras adotam cada vez mais políticas que possibilitam o auto-arquivo das publicações em repositórios institucionais, como também que existe todo um trabalho de sensibilização a percorrer, não só para os investigadores, como para a instituição e toda a sociedade. A produção de um conjunto de recomendações, que passam pela implementação de uma política institucional que incentive o auto-arquivo das publicações desenvolvidas no âmbito institucional no repositório, serve como mote para uma maior valorização da produção científica do INESC TEC.The progressive transformation of scientific practices, driven by the development of new Information and Communication Technologies (ICT), which made it possible to increase access to information, gradually moving towards an opening of the research cycle. This opening makes it possible to resolve, in the long term, the adversity that has been placed on researchers, which involves the existence of barriers that limit access conditions, whether geographical or financial. Although large commercial publishers predominantly dominate scientific production and subject it to the rules imposed by them, the Open Access movement whose first public declaration, the Budapest Declaration (BOAI), was in 2002, proposes significant changes that benefit the authors and the readers. This Movement has gained importance in Portugal since 2003, with the constitution of the first institutional repository at the national level. Institutional repositories have emerged as a tool for disseminating the scientific production of an institution to open the results of the research, both before publication and the preprint process and postprint, increase the visibility of work done by an investigator and his or her institution. The present study, which underwent an analysis of the copyright policies of INESC TEC most relevant scientific publications, allowed not only to realize that publishers are increasingly adopting policies that make it possible to self-archive publications in institutional repositories, all the work of raising awareness, not only for researchers but also for the institution and the whole society. The production of a set of recommendations, which go through the implementation of an institutional policy that encourages the self-archiving of the publications developed in the institutional scope in the repository, serves as a motto for a greater appreciation of the scientific production of INESC TEC

The Longer Term Effects of Federal Subsidies on Firm Commercialization and Survival:Evidence from the Advanced Technology Program

The goal of this dissertation is to determine the longer term (5-10 year) causal impact of federal R&D subsidies on firms’ survival outcomes and commercialization behavior. The data are small firms which applied to the 1998-2000 Advanced Technology Program (ATP) competitions. A variant of the research design pioneered by Heckman (1979) allows for inherent pre-award differences between awarded and non-awarded firms to be taken into account. This dissertation finds that receiving an ATP award has a positive and significant causal impact on a firm’s survival chances and new product announcements, but not on the more general likelihood of it commercializing any of its research.Doctor of Philosoph