Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 138-145). Also available via the Internet.

Orientador: Luiz Carlos Pereira da Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-24T07:39:20Z (GMT). No. of bitstreams: 1 Gomes_LeandroCostaFerreira_M.pdf: 6148500 bytes, checksum: bf5007e253bf40d848b0494ce01ead56 (MD5) Previous issue date: 2014 / Resumo: O presente trabalho está inserido num contexto de busca de novas fontes de energia elétrica e de aproveitamento de grandes potenciais energéticos localizados distantes dos principais centros de carga. Para estes, alternativas não convencionais de transmissão também são exigidas, nas quais se insere a transmissão em linhas de pouco mais de meio comprimento de onda, distância de pouco mais de 2500km no sistema brasileiro à 60Hz. Como este tipo de transmissão nunca foi implementado, trata-se de uma proposta inovadora, pouco explorada e que exige ensaios elementares para testar-se a viabilidade, vantagens e desvantagens frente a outras alternativas de transmissão de energia elétrica. Esta dissertação visa investigar alguns aspectos referentes à tal método de transmissão de grandes montantes de potência em distintos cenários de interligação entre as regiões Norte e Sudeste do Brasil do SIN (sistema interligado nacional). Três distintos corredores compostos por linhas de pouco mais de meio comprimento de onda foram ensaiados. Inseridos conectando a usina de Belo Monte no Pará a Assis-SP na rede de 500kV, percorrendo 2664 km. Cada um dos corredores é composto por: três linhas de 800 kV e 4846 MW de potência característica (SIL); um segundo com duas das mesmas linhas de 800kV e um terceiro com duas linhas de 1000 kV e 8100 MW de potência característica. Cada aspecto é ensaiado em seis diferentes situações de carregamento do SIN e de fluxo de potência pelo corredor, abrangendo cenários de alto, médio e baixo carregamento das linhas assim como mudanças no sentido do fluxo entre Norte e Sudeste. Dentre os aspectos abordados estão: a avaliação e redução das perdas manipulando a potência característica operacional das linhas; o controle do carregamento do corredor através do uso de transformadores defasadores não convencionais; a inserção de cargas e geração em pontos intermediários deste e o controle do fluxo de potência reativa. Por fim, o estudo não aborda aspectos transitórios e é realizado com o auxílio do ANAREDE, software elaborado pelo CEPEL / Abstract: This work is placed in a search for new sources of power and exploitation of large energy potential located far from major load centers. For the second scenarios, alternate non-conventional transmission are also required, in which half wavelength transmission lines are inserted, resulting in a distance of just over 2500km for the 60Hz brazilian electrical system. Since this type of transmission has never been implemented, it is an innovative solution and few explored, requiring elementary studies to test the feasibility, advantages and disadvantages compared to other alternatives for bulk electric power transmission. This thesis aims to investigate some aspects related to such transmission method for large amounts of power into distinct scenarios of interconnection between the North and Southeast of Brazil's SIN (Brazilian National grid). Corridors consisting of three distinct lines of just over half wavelength were tested. Inserted connecting Belo Monte hydro power plant in Para to Assis in São Paulo through the 500kV network, covering 2664 km, each corridor is composed: by three lines of 800 kV and 4846 MW of Surge Load Impedance (SIL), the second one by two of the same 800kV lines and a third by two lines of 1000 kV and 8100 MW SIL. Each aspect is tested in six different SIN load situations and power flowing through the corridor, covering scenarios of high, medium and low lines loading as well as changes in flow direction between North and Southeast. Among the issues tackled are: evaluation and reduction of losses by manipulating operating lines SIL; line load controlling using non-conventional phase shift transformers; inserting loads and generation at intermediate points of the lines and control of reactive power flow. Finally, the study does not handle with transient aspects and is accomplished with the aid of ANAREDE, software developed by CEPEL / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23207号 / 工博第4851号 / 新制||工||1757(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 篠原 真毅, 教授 守倉 正博, 准教授 久門 尚史 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21108号 / 工博第4472号 / 新制||工||1695(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 篠原 真毅, 教授 山川 宏, 教授 木本 恒暢 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / A conventionally designed radio frequency amplifier operated in its linear region exhibits low DC to RF conversion efficiency. Typically, for a power amplifier designed for digital modulation applications, the amplifier is operated “backed-off” from its P1dB point by a factor of 10 or -10 dB. The typical linear amplifier is biased for either Class A or Class A/B operation depending on the acceptable design trade-offs between efficiency and linearity between these two methods. A novel design approach to increasing the efficiency of a linear RF power amplifier using a modified Odd-Way Doherty technique is presented in this paper. The design was simulated, built and then tested. The design yields improvements in efficiency and linearity.

The increasing demand for greater capacity of mobile communications has led to the petition of more radio spectrum at 1900 MHz for the new personal communication service (PCS) systems. The PCS spectrum is proposed to coexist with current fixed microwave spectrum. This presents cochannel interference control problems which can be avoided with extensive propagation studies in both measurements and predictions. Currently, there is no readily available tool to predict propagation channels for the small coverage area that PCS operates at 1900 MHz. This thesis presents new methods for propagation prediction without relying on measurements but rather local environment geometries and their electrical properties. The propagation prediction tool developed is based on the principle of geometrical optics and Fresnel-Kirchoff diffraction. Geometrical optics enables computer software to automatically trace the propagation of radio wave energy from the transmitter to the receiver. The ray tracing techniques presented are optimized for speed with a little trade-off in accuracy. Also, efficient techniques were developed to find true diffracting building edges in dense urban environments. The propagation prediction software also rely on other commercial software packages such as AutoCAD and GRASS to maintain and manipulate the environmental database as well as displaying prediction results. The software yielded reasonable accuracy when compared against VT campus propagation measurements at 900 MHz and 1900 MHz. / Master of Science

Avec le développement de l’internet des objets et l’augmentation des applications sans fil, les antennes sont de plus en plus présentes au quotidien. Cependant, l’implantation de ces antennes est un challenge tant d’un point de vue technologique (intégration des antennes dans les dispositifs), que psychologique (acceptabilité des antennes par le grand public). Dans ce contexte, le développement d’antennes optiquement transparentes permet non seulement leur implantation sur de nouvelles surfaces (vitrages d’immeubles, écrans de smartphones ...), mais promeut aussi leur acceptabilité par le grand public grâce à leur faible impact visuel. Ce travail présente la conception, la fabrication et la caractérisation d’antennes actives optiquement transparentes. Le matériau transparent et conducteur utilisé est un maillage métallique à pas micrométrique développé spécifiquement, alliant conductivité électrique et transparence optique élevées. Dans ce cadre, un premier prototype d’antenne transparente et miniature en bande FM utilisant un transistor MESFET de dimensions sub-millimétriques a été réalisé. Des antennes agiles en fréquence en bande X (~10 GHz) couplées, soit à une diode varicap localisée (agilité ~10%), soit à un matériau ferroélectrique (agilité ~2%), ont été développées et étudiées. Une antenne passive transparente a été conçue en bande V (~60 GHz). Enfin, une transition optique (1540 nm) / hyperfréquence (1,4 GHz) a été réalisée et caractérisée, basée sur la transmission optique d’un faisceau laser au travers du matériau constitutif de l’antenne. Pour l’ensemble des prototypes réalisés, une transparence optique supérieure à 80% dans le domaine du visible associée à une résistance par carré inférieure à 0,1 ohm/sq ont été utilisées. / Within the development of the Internet of Things (IoT) and the increase of the wireless communications, antennas are even more present on everyday life. However, antenna implementation is a real challenge, from a technological point of view (antenna integration into the devices) and from a psychological point of view (acceptability by the general public). Within this framework, the development of optically transparent antennas on new surfaces (glass windows, smartphone screens . . . ) is of great interest to improve the network coverage and to assist the general public in acceptability thanks to the low visual impact of such printed antennas. The present work deals with the design, the fabrication and the characterization of optically transparent and active antennas. The transparent and conducting material used is a micrometric mesh metal film specifically developed, associating high electrical conductivity and high optical transparency. A first optically transparent and miniature FM antenna based on a MESFET transistor with micrometric size has been designed and fabricated. Frequency agile antennas operating in X-band (~10 GHz), based on a beam-lead varactor (agility ~10%) and on a ferroelectric material agility ~2%), have been developed and characterized. An optically transparent and passive antenna has been studied in V-band (~60 GHz). At last, optics (1540 nm) / microwave (1.4 GHz) transition has been performed based on the transmission of a laser beam through the transparent antenna. For all prototypes, an optical transparency level higher than 80% coupled with a sheet resistance value lower than 0.1 ohm/sq have been used.