A Smart Frequency Presetting Technique for Fast Lock-in LC-PLL Frequency Synthesizer

This paper proposes a smart frequency presetting technique for fast lock-in LC-PLL frequency synthesizer. The technique accurately presets the frequency of VCO with small initial frequency error and greatly reduces the lock-in time. It can automatically compensate preset frequency variation with process and temperature. A 2.4GHz synthesizer with 1MHz reference input was implemented in 0.35 mu m CMOS process. The chip core area is 0.4mm(2). Output frequency of VCO ranges from 2390 to 2600MHz. The measured results show that the typical lock-in time is 3 mu s. The phase noise is -112dBc/Hz at 600KHz offset from center frequency. The test chip consumes current of 22mA that includes the consumption of the I/O buffers

Quantifying, generating and mitigating radio interference in Low-Power Wireless Networks

Doctoral Programme in Telecommunication - MAP-teleRadio interference a ects the performance of low-power wireless networks (LPWN), leading to packet loss and reduced energy-e ciency, among other problems. Reliability of communications is key to expand application domains for LPWN. Since most LPWN operate in the license-free Industrial Scienti c and Medical (ISM) bands and hence share the spectrum with other wireless technologies, addressing interference is an important challenge. In this context, we present JamLab: a low-cost infrastructure to augment existing LPWN testbeds with accurate interference generation in LPWN testbeds, useful to experimentally investigate the impact of interference on LPWN protocols. We investigate how interference in a shared wireless medium can be mitigated by performing wireless channel energy sensing in low-cost and low-power hardware. For this pupose, we introduce a novel channel quality metric|dubbed CQ|based on availability of the channel over time, which meaningfully quanti es interference. Using data collected from a number of Wi-Fi networks operating in a library building, we show that our metric has strong correlation with the Packet Reception Rate (PRR). We then explore dynamic radio resource adaptation techniques|namely packet size and error correction code overhead optimisations|based on instantaneous spectrum usage as quanti ed by our CQ metric. To conclude, we study emerging fast fading in the composite channel under constructive baseband interference, which has been recently introduced in low-power wireless networks as a promising technique. We show the resulting composite signal becomes vulnerable in the presence of noise, leading to signi cant deterioration of the link, whenever the carriers have similar amplitudes. Overall, our results suggest that the proposed tools and techniques have the potential to improve performance in LPWN operating in the unlicensed spectrum, improving coexistence while maintaining energy-e ciency. Future work includes implementation in next generation platforms, which provides superior computational capacity and more exible radio chip designs.A interferência de r adio afeta o desempenho das redes de comunicação sem o de baixo consumo - low-power wireless networks (LPWN), o que provoca perdas de pacotes, diminuição da e ciência energética, entre outros problemas. A contabilidade das comunicações e importante para a expansão e adoção das LPWN nos diversos domínios de potencial aplicação. Visto que a grande maioria das LPWN partilham o espectro radioelétrico com outras redes sem o, a interferência torna-se um desafio importante. Neste contexto, apresentamos o JamLab: uma infraestrutura de baixo custo para estender a funcionalidade dos ambientes laboratoriais para o estudo experimental do desempenho das LPWN sob interferência. Resultando, assim, numa ferramenta essencial para a adequada verificação dos protocolos de comunicações das LPWN. Para al em disso, a Tese introduz uma nova técnica para avaliar o ambiente radioelétrico e demostra a sua utilização para gerir recursos disponíveis no transceptor rádio, o que permite melhorar a fiabilidade das comunicações, nomeadamente nas plataformas de baixo consumo, garantindo e ciência energética. Assim, apresentamos uma nova métrica| denominada CQ - concebida especificamente para quantificar a qualidade do canal r adio, com base na sua disponibilidade temporal. Mediante dados adquiridos em v arias redes sem o Wi-Fi, instaladas no edifício de uma biblioteca universitária, demonstra-se que esta métrica tem um ótimo desempenho, evidenciando uma elevada correlação com a taxa de receção de pacotes. Investiga-se ainda a potencialidade da nossa métrica CQ para gerir dinamicamente recursos de radio como tamanho de pacote e taxa de correlação de erros dos códigos - baseado em medições instantâneas da qualidade do canal de radio. Posteriormente, estuda-se um modelo de canal composto, sob interferência construtiva de banda-base. A interferência construtiva de banda-base tem sido introduzida recentemente nas LPWN, evidenciando ser uma técnica prometedora no que diz respeito à baixa latência e à contabilidade das comunicações. Na Tese investiga-se o caso crítico em que o sinal composto se torna vulnerável na presença de ruído, o que acaba por deteriorar a qualidade da ligação, no caso em que as amplitudes das distintas portadoras presentes no receptor sejam similares. Finalmente, os resultados obtidos sugerem que as ferramentas e as técnicas propostas têm potencial para melhorar o desempenho das LPWN, num cenário de partilha do espectro radioelétrico com outras redes, melhorando a coexistência e mantendo e ciência energética. Prevê-se como trabalho futuro a implementação das técnicas propostas em plataformas de próxima geração, com maior flexibilidade e poder computacional para o processamento dos sinais rádio.This work was supported by FCT (Portuguese Foundation for Science and Technology) and by ESF (European Social Fund) through POPH (Portuguese Human Potential Operational Program), under PhD grant SFRH/BD/62198/2009; also by FCT under project ref. FCOMP-01-0124-FEDER-014922 (MASQOTS), and EU through the FP7 programme, under grant FP7-ICT-224053 (CONET)

The 25th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting

Papers in the following categories are presented: recent developments in rubidium, cesium, and hydrogen-based frequency standards, and in cryogenic and trapped-ion technology; international and transnational applications of precise time and time interval (PTTI) technology with emphasis on satellite laser tracking networks, GLONASS timing, intercomparison of national time scales and international telecommunication; applications of PTTI technology to the telecommunications, power distribution, platform positioning, and geophysical survey industries; application of PTTI technology to evolving military communications and navigation systems; and dissemination of precise time and frequency by means of GPS, GLONASS, MILSTAR, LORAN, and synchronous communications satellites

Large space structures and systems in the space station era: A bibliography with indexes (supplement 05)

Bibliographies and abstracts are listed for 1363 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1991 and July 31, 1992. Topics covered include technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion and solar power satellite systems