Transmissores reconfiguráveis para rádios definidos por software

Doutoramento em Engenharia ElectrotécnicaFlexible radio transmitters based on the Software-Defined Radio (SDR) concept are gaining an increased research importance due to the unparalleled proliferation of new wireless standards operating at different frequencies, using dissimilar coding and modulation schemes, and targeted for different ends. In this new wireless communications paradigm, the physical layer of the radio transmitter must be able to support the simultaneous transmission of multi-band, multi-rate, multi-standard signals, which in practice is very hard or very inefficient to implement using conventional approaches. Nevertheless, the last developments in this field include novel all-digital transmitter architectures where the radio datapath is digital from the baseband up to the RF stage. Such concept has inherent high flexibility and poses an important step towards the development of SDR-based transmitters. However, the truth is that implementing such radio for a real world communications scenario is a challenging task, where a few key limitations are still preventing a wider adoption of this concept. This thesis aims exactly to address some of these limitations by proposing and implementing innovative all-digital transmitter architectures with inherent higher flexibility and integration, and where improving important figures of merit, such as coding efficiency, signal-to-noise ratio, usable bandwidth and in-band and out-of-band noise will also be addressed. In the first part of this thesis, the concept of transmitting RF data using an entirely digital approach based on pulsed modulation is introduced. A comparison between several implementation technologies is also presented, allowing to state that FPGAs provide an interesting compromise between performance, power efficiency and flexibility, thus making them an interesting choice as an enabling technology for pulse-based all-digital transmitters. Following this discussion, the fundamental concepts inherent to pulsed modulators, its key advantages, main limitations and typical enhancements suitable for all-digital transmitters are also presented. The recent advances regarding the two most common classes of pulse modulated transmitters, namely the RF and the baseband-level are introduced, along with several examples of state-of-the-art architectures found on the literature. The core of this dissertation containing the main developments achieved during this PhD work is then presented and discussed. The first key contribution to the state-of-the-art presented here consists in the development of a novel ΣΔ-based all-digital transmitter architecture capable of multiband and multi-standard data transmission in a very flexible and integrated way, where the pulsed RF output operating in the microwave frequency range is generated inside a single FPGA device. A fundamental contribution regarding the simultaneous transmission of multiple RF signals is then introduced by presenting and describing novel all-digital transmitter architectures that take advantage of multi-gigabit data serializers available on current high-end FPGAs in order to transmit in a time-interleaved approach multiple independent RF carriers. Further improvements in this design approach allowed to provide a two-stage up-conversion transmitter architecture enabling the fine frequency tuning of concurrent multichannel multi-standard signals. Finally, further improvements regarding two key limitations inherent to current all-digital transmitter approaches are then addressed, namely the poor coding efficiency and the combined high quality factor and tunability requirements of the RF output filter. The followed design approach based on poliphase multipath circuits allowed to create a new FPGA-embedded agile transmitter architecture that significantly improves important figures of merit, such as coding efficiency and SNR, while maintains the high flexibility that is required for supporting multichannel multimode data transmission.Transmissores de rádio flexíveis baseados no conceito do Rádio Definido por Software (SDR) estão a receber uma crescente importância de investigação essencialmente devido à proliferação sem precedentes de novos standards de comunicações wireless que trabalham em frequências diferentes, usando esquemas de modulação e codificação dissimilares, estando direcionados para os mais diversos fins. Neste novo paradigma de comunicações wireless, a camada física do transmissor rádio tem de ser capaz de suportar a transmissão simultânea de sinais provenientes de diferentes standards, operando em diferentes bandas de frequências e com diferentes ritmos de transmissão, o que na prática é muito difícil ou muito ineficiente de implementar utilizando abordagens convencionais. Contudo, os últimos desenvolvimentos nesta área incluem novas arquiteturas de transmissão inteiramente digitais onde o datapath do rádio é digital desde a banda base até ao RF. Tal conceito tem uma elevada flexibilidade e representa um passo importante para o desenvolvimento de transmissores baseados em SDR. No entanto, a implementação de tal rádio para cenários de comunicação reais é uma tarefa desafiadora, onde algumas limitações chave estão ainda impedindo uma maior adopção deste conceito. Esta tese tem como principal objetivo o de investigar algumas destas limitações, propondo e implementando arquiteturas inovadoras de transmissão inteiramente digitais com inerente elevada flexibilidade e integração, e onde melhorar importantes figuras de mérito, tais como a eficiência de codificação, a relação sinal-ruído, a largura de banda utilizável e o ruído dentro e fora da banda também serão abordadas. Na primeira parte deste trabalho é introduzido o conceito de transmissão de dados RF utilizando uma abordagem totalmente digital, baseada em modulação por impulsos. Uma comparação entre diversas tecnologias de implementação é também apresentada, permitindo afirmar que as FPGAs actuais oferecem um compromisso interessante entre desempenho, eficiência de energia e flexibilidade, tornando-as uma escolha interessante como uma tecnologia de implementação com elevado potencial para transmissores completamente digitais baseados em moduladores pulsados. Após esta discussão são apresentados os conceitos fundamentais inerentes aos moduladores pulsados e introduzidos os avanços relativos a transmissores RF modulados por pulsos, juntamente com vários exemplos de arquiteturas do estado da arte encontrados na literatura. Em seguida, o núcleo desta tese contendo os principais desenvolvimentos alcançados durante este trabalho de doutoramento é apresentado e discutido. O primeiro contributo fundamental para o estado da arte aqui apresentado consiste no desenvolvimento e integração em FPGA de uma nova arquitetura de transmissão inteiramente digital, baseada em moduladores ΣΔ e dotada de uma elevada flexibilidade e integração, sendo capaz de transmitir dados de multiplos standards e em multiplas bandas de RF. Uma segunda contribuição chave relativa à transmissão simultânea de vários sinais RF é então introduzida, sendo apresentadas e descritas novas arquiteturas de transmissão de sinal RF inteiramente digitais, as quais tiram proveito de serializadores de dados multi-gigabit disponíveis em FPGAs atuais de alto desempenho. Melhorias adicionais a esta abordagem permitiram desenvolver uma arquitetura de transmissão com duas fases de conversão na frequência, a qual permite a transmissão concorrente de sinais multistandard e multicanal com ajuste fino na frequência. Por ultimo, foram ainda investigadas diversas técnicas que visam reduzir duas limitações fundamentais inerentes aos actuais transmissores completamente digitais, nomeadamente, a baixa eficiência de codificação dos moduladores pulsados e o elevado fator de qualidade combinado com elevados requisitos de adaptabilidade na frequencia do filtro de reconstrução do sinal RF a transmitir. A abordagem seguida baseada em multiplos caminhos polifásicos permitiu desenvolver uma nova arquitetura de transmissão integrada em FPGA que melhora de forma significativa importantes figuras de mérito, tais como a eficiência de codificação e SNR, enquanto mantém a elevada flexibilidade que é necessária para suportar a transmissão de dados multimodo e multicanal

Executivo de tempo-real para processadores embutidos em FPGA

Mestrado em Engenharia Electrónica e TelecomunicaçõesDevido `a grande evolu¸c˜ao da tecnologia microelectr´onica ao longo das ´ultimas d´ecadas, actualmente ´e poss´ıvel a constru¸c˜ao de circuitos integrados extremamente complexos, contendo diversas centenas de milh˜oes de trans´ıstores. Este facto tornou o conceito de sistema integrado uma realidade. Uma das consequˆencias da evolu¸c˜ao da tecnologia foi a disponibiliza ¸c˜ao de dispositivos l´ogicos complexos reconfigur´aveis como as FPGAs. Tais dispositivos permitem o desenvolvimento de sistemas integrados, com a vantagem de possibilitarem uma r´apida fase de prototipagem. A crescente capacidade computacional e a redu¸c˜ao do tamanho levaram a que os microprocessadores passassem a estar embutidos em muitos dos equipamentos e aplica¸c˜oes do quotidiano. Dependendo da aplica¸c˜ao que o sistema embutido ir´a desempenhar, pode existir a necessidade da sua execu¸c˜ao em intervalos de tempo bem definidos, e um atraso temporal na resposta a um determinado est´ımulo pode significar o colapso no controlo de todo um processo. Tais sistemas possuem restri¸c˜oes de tempo-real e requerem abordagens de concep¸c˜ao adequadas para o seu correcto funcionamento. A grande motiva¸c˜ao para a realiza¸c˜ao deste trabalho consistiu na possibilidade de integrar num ´unico dispositivo f´ısico reconfigur´avel, todos os componentes de uma arquitectura computacional especializada para sistemas de tempo-real, ou seja, integrar processador, mem´oria, perif´ericos, executivo de tempo-real e aplica¸c˜ao, num ´unico dispositivo f´ısico. Nesta disserta¸c˜ao s˜ao discutidas ideias, apresentadas arquitecturas e avaliadas implementa¸c˜oes de um executivo de tempo-real para processadores embutidos em FPGA. O principal objectivo deste trabalho consiste em integrar e avaliar um executivo de tempo-real embutido em FPGA. O ponto de partida deste trabalho foi a constru¸c˜ao de um sistema integrado em FPGA, recorrendo `as ferramentas de desenvolvimento Xilinx EDK (Embedded Development Kit). O sistema desenvolvido, designado por MB-SoC (MicroBlaze - System-on-Chip), re´une um conjunto de perif´ericos, dispositivos de entrada/sa´ıda, mem´oria e o processador sintetiz´avel MicroBlaze implementado em blocos l´ogicos configur´aveis da FPGA. Posteriormente foi ainda desenvolvido um segundo sistema, designado por PPC-SoC (PowerPC 405 - SoC). Este ´e idˆentico ao anterior, mas utiliza um processador de alto desempenho, implementado em l´ogica dedicada e interno `a FPGA. O executivo de tempo-real OReK (Object-oriented Real-time Kernel) foi portado, no ˆambito deste trabalho, para os sistemas integrados desenvolvidos, MB-SoC e PPC-SoC. Os resultados da avalia¸c˜ao efectuada permitem analisar as vantagens e as desvantagens, associadas `as diversas implementa¸c˜oes. ABSTRACT: Due to the great development of microelectronics technology over recent decades, today it is possible the construction of extremely complex integrated circuits, containing several hundred million transistors. This made the System-on-Chip concept a reality. One of the consequences of the evolution of technology was the provision of complex logic devices such as reconfigurable FPGAs. Such devices allow the System-on-Chip development with the advantage of allowing a rapid prototyping phase. The increasing computational capacity and the reduction of the size led the microprocessors to be embedded in many of the equipment and applications in everyday life. Depending on the application that the embedded system will do, there may be a need for execution at well defined intervals of time, and a time delay in responding to a stimulus can mean the collapse in control of an entire process. Such systems have real-time restrictions and require appropriate design approaches for the proper functioning. The major motivation for this work was the possibility of integrating into a single physical reconfigurable device, all components of an computational architecture specialized for real-time systems. In this dissertation ideas are discussed, presented architectures and evaluated implementations of a real-time executive for embedded processors in FPGA. The main objective of this work is to integrate and evaluate an executive of real-time, embedded in FPGA. The starting point of this work was the construction of an FPGA System-on- Chip, using the development tools named Xilinx EDK (Embedded Development Kit). The developed system, named MB-SoC (MicroBlaze - Systemon- Chip), gathers a set of peripherals, input/output devices, memory and the soft-core MicroBlaze processor implemented in FPGA configurable logic blocks. Later was developed a second system, named PPC-SoC (PowerPC 405 - SoC). This is identical to the previous, but uses an high performance processor, implemented in dedicated logic and internal to the FPGA. The real-time executive OReK (Object-oriented Real-time Kernel) was ported, within this work, to the developed integrated systems, MB-SoC and PPC-SoC. The results of the evaluation can analise the advantages and the disadvantages, associated to the various implementations

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

SARS-CoV-2 introductions and early dynamics of the epidemic in Portugal

Genomic surveillance of SARS-CoV-2 in Portugal was rapidly implemented by the National Institute of Health in the early stages of the COVID-19 epidemic, in collaboration with more than 50 laboratories distributed nationwide. Methods By applying recent phylodynamic models that allow integration of individual-based travel history, we reconstructed and characterized the spatio-temporal dynamics of SARSCoV-2 introductions and early dissemination in Portugal. Results We detected at least 277 independent SARS-CoV-2 introductions, mostly from European countries (namely the United Kingdom, Spain, France, Italy, and Switzerland), which were consistent with the countries with the highest connectivity with Portugal. Although most introductions were estimated to have occurred during early March 2020, it is likely that SARS-CoV-2 was silently circulating in Portugal throughout February, before the first cases were confirmed. Conclusions Here we conclude that the earlier implementation of measures could have minimized the number of introductions and subsequent virus expansion in Portugal. This study lays the foundation for genomic epidemiology of SARS-CoV-2 in Portugal, and highlights the need for systematic and geographically-representative genomic surveillance.We gratefully acknowledge to Sara Hill and Nuno Faria (University of Oxford) and Joshua Quick and Nick Loman (University of Birmingham) for kindly providing us with the initial sets of Artic Network primers for NGS; Rafael Mamede (MRamirez team, IMM, Lisbon) for developing and sharing a bioinformatics script for sequence curation (https://github.com/rfm-targa/BioinfUtils); Philippe Lemey (KU Leuven) for providing guidance on the implementation of the phylodynamic models; Joshua L. Cherry (National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health) for providing guidance with the subsampling strategies; and all authors, originating and submitting laboratories who have contributed genome data on GISAID (https://www.gisaid.org/) on which part of this research is based. The opinions expressed in this article are those of the authors and do not reflect the view of the National Institutes of Health, the Department of Health and Human Services, or the United States government. This study is co-funded by Fundação para a Ciência e Tecnologia and Agência de Investigação Clínica e Inovação Biomédica (234_596874175) on behalf of the Research 4 COVID-19 call. Some infrastructural resources used in this study come from the GenomePT project (POCI-01-0145-FEDER-022184), supported by COMPETE 2020 - Operational Programme for Competitiveness and Internationalisation (POCI), Lisboa Portugal Regional Operational Programme (Lisboa2020), Algarve Portugal Regional Operational Programme (CRESC Algarve2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF), and by Fundação para a Ciência e a Tecnologia (FCT).info:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Introdução das tecnologias de informação e comunicação em escolas do 1º ciclo

[Resumo] A integrac;ao das Tecnologias de Informação e Comunicação em projectos educativos nas Escolas do Primeiro Ciclo do Ensino Básico e Jardins de Infancia, em Portugal, conheceu, desde 1996, um forte incentivo com o aparecimento do Programa Nónio Século XXI, do Ministério da Educação. Os Centros de Competencia Nónio, entao criados, com o objectivo de acompanharem os projectos das escolas, constituem urna estrutura intermédia de acompanhamento e dinamização dos projectos eujo impacto se será possível conhecer ou reconhecer com estudos aprofundados que contemplem diversas vertentes pedagógicas, técnicas, metodológicas e estratégicas que estao por fazer. O Centro de Competencia da Universidade do Minho, englobando internamente duas escolas voltadas para a formação inicial de professores, pretende esboc;ar, neste pequeno espaço, um quadro referencial de análise a importancia da integração tecnológica nas escolas do nível inicial da escolaridade obrigatória. Desta forma, este texto pretende realçar, ainda que de forma pouco aprofundada, as estratégias utilizadas por esses estabelecimentos de ensino, as vicissitudes encontradas e os resultados obtidos, mesmo que urnas e outros se apontem apenas ao de leve . No fulcro deste documento aparece a perspectiva da equipa que acompanha as Escolas do Primeiro Ciclo e os Jardins de Infancia que corajosamente se lançaram na integração das TIC em projectos curriculares, tentando fazer realçar alguns aspectos que a experiencia nos avisa para ter em cont