Melhoria da eficiência de amplificadores de potência para sinais RF com envolvente variável

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Electrónica e Telecomunicações

A VLF to UHF propagation model for evaluation of high-speed railway electromagnetic interference in RF monitoring base-stations

Considering that recent european high-speed railway system has a traction power system of kV 50 Hz, which causes electromagnetic emission for the outside world, it is important to dimension the railway system emissions, using a frequency/distance dependent propagation model. This paper presents an enhanced theoretical model for VLF to UHF propagation, railway system oriented. It introduces the near field approach (crucial in low frequency propagation) and also considers the source characteristics and type of measuring antenna. Simulations are presented, and comparisons are set with earlier far field models. Using the developed model, a real case study was performed in partnership with Refer Telecom (portuguese telecom operator for railways). The new propagation model was used in order to predict the future high-speed railway electromagnetic emissions in the Lisbon north track. The results show the model's prediction capabilities and also its applicability to realistic scenarios.

Design and evaluation of multi-band RF energy harvesting circuits and antennas for WSNs

Radio frequency (RF) energy harvesting is an emerging technology that will enable to drive the next generation of wireless sensor networks (WSNs) without the need of using batteries. In this paper, we present RF energy harvesting circuits specifically developed for GSM bands (900/1800) and a wearable dual-band antenna suitable for possible implementation within clothes for body worn applications. Besides, we address the development and experimental characterization of three different prototypes of a five-stage Dickson voltage multiplier (with match impedance circuit) responsible for harvesting the RF energy. Different printed circuit board (PCB) fabrication techniques to produce the prototypes result in different values of conversion efficiency. Therefore, we conclude that if the PCB fabrication is achieved by means of a rigorous control in the photo-positive method and chemical bath procedure applied to the PCB it allows for attaining better values for the conversion efficiency. All three prototypes (1, 2 and 3) can power supply the IRIS sensor node for RF received powers of -4 dBm, -6 dBm and -5 dBm, and conversion efficiencies of 20, 32 and 26%, respectively. © 2014 IEEE.

Automated synthesis procedure of RF discrete tuning differential capacitance circuits

The paper presents a RFDSCA automated synthesis procedure. This algorithm determines several RFDSCA circuits from the top-level system specifications all with the same maximum performance. The genetic synthesis tool optimizes a fitness function proportional to the RFDSCA quality factor and uses the epsiv-concept and maximin sorting scheme to achieve a set of solutions well distributed along a non-dominated front. To confirm the results of the algorithm, three RFDSCAs were simulated in SpectreRF and one of them was implemented and tested. The design used a 0.25 mum BiCMOS process. All the results (synthesized, simulated and measured) are very close, which indicate that the genetic synthesis method is a very useful tool to design optimum performance RFDSCAs.

An high-speed parametric ADC and a co-designed mixer for CMOS RF receivers

Dissertação apresentada na faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Engenharia Electrotécnica e de Computadores

Low power low voltage quadrature RC oscillators for modern RF receivers

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Engenharia Electrotécnica e de Computadores

Automated Synthesis Procedure of RF Discrete Tuning Differential Capacitance Circuits

The paper presents a RFDSCA automated synthesis procedure. This algorithm determines several RFDSCA circuits from the top-level system specifications all with the same maximum performance. The genetic synthesis tool optimizes a fitness function proportional to the RFDSCA quality factor and uses the epsiv-concept and maximin sorting scheme to achieve a set of solutions well distributed along a non-dominated front. To confirm the results of the algorithm, three RFDSCAs were simulated in SpectreRF and one of them was implemented and tested. The design used a 0.25 mum BiCMOS process. All the results (synthesized, simulated and measured) are very close, which indicate that the genetic synthesis method is a very useful tool to design optimum performance RFDSCAs.

Monitorização e otimização da deposição de filmes de óxidos mistos por RF-sputtering

Dissertação para obtenção do Grau de Mestre em Engenharia Física

An RF LC Q-enhanced CMOS iter using integrated inductors with layout optimization

Dissertação apresentada para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia

A low-voltage RF-CMOS receiver front-end for a wireless fall detection microsystem

Dissertação para obtenção do Grau de Mestre em Engenharia Eletrotécnica e de Computadores, pela Universidade Nova de Ciências e Tecnologia

Modeling of integrated inductors for RF circuit design

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica

Design of a low-voltage CMOS RF receiver for energy harvesting sensor node

In this thesis a CMOS low-power and low-voltage RF receiver front-end is presented. The main objective is to design this RF receiver so that it can be powered by a piezoelectric energy harvesting power source, included in a Wireless Sensor Node application. For this type of applications the major requirements are: the low-power and low-voltage operation, the reduced area and cost and the simplicity of the architecture. The system key blocks are the LNA and the mixer, which are studied and optimized with greater detail, achieving a good linearity, a wideband operation and a reduced introduction of noise. A wideband balun LNA with noise and distortion cancelling is designed to work at a 0.6 V supply voltage, in conjunction with a double-balanced passive mixer and subsequent TIA block. The passive mixer operates in current mode, allowing a minimal introduction of voltage noise and a good linearity. The receiver analog front-end has a total voltage conversion gain of 31.5 dB, a 0.1 - 4.3 GHz bandwidth, an IIP3 value of -1.35 dBm, and a noise figure lower than 9 dB. The total power consumption is 1.9 mW and the die area is 305x134.5 m2, using a standard 130 nm CMOS technology.

Ablação com RF de arritmia na infância: registro observacional em 125 crianças

FUNDAMENTO: Ablação por radiofrequência (ARF) em crianças consiste em uma prática cada vez mais frequente. OBJETIVO: Avaliar, em nossa instituição, os resultados da ARF em crianças com idade abaixo de 15 anos. MÉTODOS: Foram analisadas 125 crianças submetidas à ARF entre maio de 1991 a maio de 2010. RESULTADOS: Sessenta e sete (53,6%) crianças eram do sexo masculino, com idade entre 44 dias e 15 anos (média de 8,6 ± 3,3 anos) e peso mediano de 31 kg. Cardiopatia esteve presente em 21 (16,8%) pacientes. A ARF de vias acessórias (VA) foi o procedimento mais comum (62 crianças - 49,6%). A ARF de taquicardias por reentrada nodal (TRN) foi a segunda arritmia mais frequente, em 27 (21,6%), seguida de taquicardias atriais (TA), em 16 (12,8%) e de taquicardias ventriculares (TV) em 8 (6,4%) crianças. Os critérios de sucesso foram alcançados em 86,9%, 96,1%, 80% e 62,5% dos pacientes submetidos à ARF de VA, TRN, TA e TV, respectivamente. Os bloqueios atrioventriculares transitórios (BAVT) ocorreram durante a ARF em 4 (3,2%) e BRD em 7 (5,6%) crianças. Vinte e cinco crianças foram submetidos à nova ARF por insucesso inicial ou recorrência. Durante o seguimento médio de 5,5 ± 3,4 anos, 107 (88,4%) persistiram sem recorrência. Não houve diferença estatística em relação aos resultados e à idade em que o paciente se submeteu ao procedimento. Nenhuma criança apresentou BAVT persistente ou necessitou de marca-passo definitivo. CONCLUSÃO: A ablação por cateter é uma alternativa terapêutica segura e eficiente em crianças com taquicardias recorrentes refratárias ao tratamento clínico.

Analysis, design, optimization and realization of compact high performance printed RF filters

Magdeburg, Univ., Fak. für Elektrotechnik und Informationstechnik, Diss., 2010

RR Voor RF (Triptych)

Combined media on photographic paper. 104" x 170"