Incertezas de modelo invadem todos os estágios de uma análise de confiabilidade estrutural, desde a determinação das ações e do próprio sistema estrutural, até o processo pelo qual o efeito destas ações é avaliado. Neste trabalho, o enfoque é dado nesse último tópico, mais especificamente na avaliação das incertezas de modelo mecânico em torres metálicas treliçadas de linhas de transmissão (LT), o qual tem permanecido ignorado nas estimativas de confiabilidade até então, em parte devido a sua natureza elusiva. Logo, o problema consiste em avaliar as incertezas na predição da resposta estrutural, uma vez que todos os parâmetros que definem as ações externas e o próprio sistema são claramente definidos. A principal motivação deste trabalho partiu de um estudo conduzido pela CIGRÉ sobre torres metálicas treliçadas de LT submetidas a cargas estáticas, o qual sugere que as incertezas de modelo neste tipo de estrutura são relevantes e não podem ser desprezadas, podendo influenciar significativamente na estimativa da confiabilidade. Neste trabalho, são avaliados diferentes modelos mecânicos de torres de LT sujeitos a ações estáticas, além de modelos de torres e trechos de LT submetidos à ação dinâmica de ruptura de cabo, adotada por ser um carregamento dinâmico “bem definido”. Na análise estática, são estudados desde modelos simplificados de torres autoportantes, adotados na prática usual de projeto, até modelos mais aprimorados. A dispersão nos resultados numéricos entre os modelos é usada para quantificar as incertezas relacionadas ao modelo mecânico, e os resultados disponíveis de ensaios estáticos em protótipos são utilizados para encontrar os modelos cuja resposta mais se aproxima dos valores experimentais. A resposta dinâmica de torres metálicas treliçadas de LT submetidas à ruptura de cabo, é comparada entre vários modelos, com diferentes graus de sofisticação e detalhe. São estudados desde o modelo usual de análise e projeto de torres para este tipo de carregamento, passando por modelos relativamente simples, com uma única torre sujeita a uma carga variável no tempo, simulando o efeito da ruptura de um cabo, até modelos mais complexos de trechos de LT, os quais incluem várias torres, cabos e cadeias de isoladores. Diversas fontes de incerteza são avaliadas, considerando a influência de fatores relevantes tais como: a discretização dos elementos de cabo, as condições de contorno dos elementos de cabo das extremidades, as leis constitutivas dos elementos de barra e de cabo e o amortecimento estrutural. Por fim, são discutidas e apresentadas possíveis maneiras de considerar explicitamente a incerteza de modelo na estimativa da confiabilidade e em códigos de projeto de estruturas de linhas de transmissão. / Model uncertainties pervade all stages of a structural reliability analysis, from the description of loads and the system itself, to the process by which the effect of loads on the system is evaluated. In this study, attention is focused on the last issue, specifically in the evaluation of model uncertainties on transmission lines (TL) latticed steel towers, which has remained largely ignored in previous developments of structural reliability, in part due to its elusive nature. In essence, the problem consists of evaluating the uncertainty in response predictions, once all parameters that define the external actions and the system itself have been unequivocally prescribed. The main motivation of this thesis was a study conducted by CIGRÉ on TL latticed steel towers subjected to static loads, among other exploratory assessments, which suggests that model uncertainty is a relevant factor and cannot be disregarded, could significantly influence the outcome of reliability assessments. Herein, different mechanical models of TL self-supporting towers subjected to static loads are evaluated, besides the models of towers and TL segments submitted to dynamic load due to cable rupture, adopted by being a “well defined” loading. In the static analysis, from simplified models of self-supporting towers, like adopted in usual practice of project, to more refined models are studied. The dispersion in the numeric results among the models, together with the data of static prototype tests, are used to quantify model uncertainties. The dynamic response of latticed TL steel towers subjected to cable rupture is predicted by use of various models with different degrees of sophistication or detailing. The predictions of the various models are compared with the aim of quantifying model uncertainty. Several uncertainty sources are evaluated, considering the influence of relevant factors such as: the discretization of the cable elements, the boundary conditions of the end cable elements, the constitutive laws of cables and tower members and the structural damping. Finally, possible ways to explicitly consider model uncertainty in reliability assessments and in code formulations are discussed.

Este trabalho fundamenta-se no desenvolvimento e aprimoramento de metodologias para a melhor representação do aterramento elétrico sob uma análise transiente. O estudo concentrase no estabelecimento de contribuições ao estado da arte associadas à análise e modelagem de aterramento impulsivo e em altas frequências. O estudo vincula-se também à avaliação da suportabilidade de seres humanos submetidos a potenciais produzidos na superfície do solo, provenientes da corrente elétrica gerada por um surto atmosférico. A concepção das metodologias propostas baseou-se no uso do Método da Modelagem por Linhas de Transmissão em uma dimensão (TLM-1D). Destacam-se três grandes tópicos da pesquisa. O primeiro concentra-se no desenvolvimento de formulação para a inclusão do fenômeno de ionização do solo ao Método TLM-1D clássico. A formulação desenvolvida tem como característica ser uma técnica generalista, independente das propriedades do meio, dimensões do eletrodo e do surto atmosférico. O segundo foco concentra-se no aprimoramento e desenvolvimento de equacionamento analítico para a estimação de potenciais gerados na superfície do solo, originados pela corrente elétrica estabelecida sobre eletrodo de aterramento. Tal equacionamento tem grande aplicabilidade em conjunto com metodologias numéricas unidimensionais, as quais não são capazes de determinar diretamente os referidos potenciais. Por fim, a realização de estudo de suportabilidade e segurança de seres humanos em contato com eletrodos de aterramento submetidos a surto atmosférico, considerando modelo representativo baseado em circuitos elétricos, consolida o trabalho desenvolvido. / This work is based on the development and improvement of methodologies for the best representation of the electrical grounding under a transient analysis. The study concentrated on establishing contributions to the state of the art related to the analysis and modeling of impulsive and high frequencies grounding systems. The study is also associated to the evaluation of the supportability of human beings submitted to the potentials produced on the soil surface from the electric current generated by a lightning. The conception of the proposed methodology was based on the Transmission Line Modeling Method in one dimension (TLM- 1D). Three major research topics can be highlighted. The first involves the development of a formulation to include the soil ionization phenomenon in the classic TLM-1D algorithm. The developed formulation is a generalist technique, independent of the medium properties, characteristic of the electrode and lightning surge. The second aims at the improvement and development of analytical equations for estimating the generated potential on the soil surface, originated by the electric current calculated in the grounding electrode. Such equationing has great applicability in conjunction with one-dimensional numerical methods which are not able to determine such potential directly. Finally, the achievement of a supportability study and personal safety of humans in contact with the grounding electrodes subjected to a lightning, considering a representative model based on electrical circuits, consolidates the developed work.

Dans le contexte des Sciences de l’Information et de la Technologie, un des challenges est de créer des systèmes de plus en plus petits embarquant de plus en plus d’intelligence au niveau matériel et logiciel avec des architectures communicantes de plus en plus complexes. Ceci nécessite des méthodologies robustes de conception afin de réduire le cycle de développement et la phase de prototypage. Ainsi, la conception et l’optimisation de la couche physique de communication est primordiale. La complexité de ces systèmes rend difficile leur optimisation notamment à cause de l’explosion du nombre des paramètres inconnus. Les méthodes et outils développés ces dernières années seront à terme inadéquats pour traiter les problèmes qui nous attendent. Par exemple, la propagation des ondes dans une cabine d’avion à partir des capteurs ou même d’une antenne, vers le poste de pilotage est grandement affectée par la présence de la structure métallique des sièges à l’intérieur de la cabine, voir les passagers. Il faut, donc, absolument prendre en compte cette perturbation pour prédire correctement le bilan de puissance entre l’antenne et un possible récepteur. Ces travaux de recherche portent sur les aspects théoriques et de mise en oeuvre pratique afin de proposer des outils informatiques pour le calcul rigoureux de la réflexion des champs électromagnétiques à l’intérieur de très grandes structures . Ce calcul implique la solution numérique de très grands systèmes inaccessibles par des ressources traditionnelles. La solution sera basée sur une grille de calcul et un supercalculateur. La modélisation électromagnétique des structures surdimensionnées par plusieurs méthodes numériques utilisant des nouvelles ressources informatiques, hardware et software, pour dérouler des calculs performants, représente le but de ce travail. La modélisation numérique est basée sur une approche hybride qui combine la méthode Transmission-Line Matrix (TLM) et l’approche modale. La TLM est appliquée aux volumes homogènes, tandis que l’approche modale est utilisée pour décrire les structures planaires complexes. Afin d’accélérer la simulation, une implémentation parallèle de l’algorithme TLM dans le contexte du paradigme de calcul distribué est proposé. Le sous-domaine de la structure qui est discrétisé avec la TLM est divisé en plusieurs parties appelées tâches, chacune étant calculée en parallèle par des processeurs différents. Pour accomplir le travail, les tâches communiquent entre elles au cours de la simulation par une librairie d’échange de messages. Une extension de l’approche modale avec plusieurs modes différents a été développée par l’augmentation de la complexité des structures planaires. Les résultats démontrent les avantages de la grille de calcul combinée avec l’approche hybride pour résoudre des grandes structures électriques, en faisant correspondre la taille du problème avec le nombre de ressources de calcul utilisées. L’étude met en évidence le rôle du schéma de parallélisation, cluster versus grille, par rapport à la taille du problème et à sa répartition. En outre, un modèle de prédiction a été développé pour déterminer les performances du calcul sur la grille, basé sur une approche hybride qui combine une prédiction issue d’un historique d’expériences avec une prédiction dérivée du profil de l’application. Les valeurs prédites sont en bon accord avec les valeurs mesurées. L’analyse des performances de simulation a permis d’extraire des règles pratiques pour l’estimation des ressources nécessaires pour un problème donné. En utilisant tous ces outils, la propagation du champ électromagnétique à l’intérieur d’une structure surdimensionnée complexe, telle qu’une cabine d’avion, a été effectuée sur la grille et également sur le supercalculateur. Les avantages et les inconvénients des deux environnements sont discutés. / In the context of Information Communications Technology (ICT), the major challenge is to create systems increasingly small, boarding more and more intelligence, hardware and software, including complex communicating architectures. This requires robust design methodologies to reduce the development cycle and prototyping phase. Thus, the design and optimization of physical layer communication is paramount. The complexity of these systems makes them difficult to optimize, because of the explosion in the number of unknown parameters. The methods and tools developed in past years will be eventually inadequate to address problems that lie ahead. Communicating objects will be very often integrated into cluttered environments with all kinds of metal structures and dielectric larger or smaller sizes compared to the wavelength. The designer must anticipate the presence of such barriers in the propagation channel to establish properly link budgets and an optimal design of the communicating object. For example, the wave propagation in an airplane cabin from sensors or even an antenna, towards the cockpit is greatly affected by the presence of the metal structure of the seats inside the cabin or even the passengers. So, we must absolutely take into account this perturbation to predict correctly the power balance between the antenna and a possible receiver. More generally, this topic will address the theoretical and computational electromagnetics in order to propose an implementation of informatics tools for the rigorous calculation of electromagnetic scattering inside very large structures or radiation antenna placed near oversized objects. This calculation involves the numerical solution of very large systems inaccessible by traditional resources. The solution will be based on grid computing and supercomputers. Electromagnetic modeling of oversized structures by means of different numerical methods, using new resources (hardware and software) to realize yet more performant calculations, is the aim of this work. The numerical modeling is based on a hybrid approach which combines Transmission-Line Matrix (TLM) and the mode matching methods. The former is applied to homogeneous volumes while the latter is used to describe complex planar structures. In order to accelerate the simulation, a parallel implementation of the TLM algorithm in the context of distributed computing paradigm is proposed. The subdomain of the structure which is discretized upon TLM is divided into several parts called tasks, each one being computed in parallel by different processors. To achieve this, the tasks communicate between them during the simulation by a message passing library. An extension of the modal approach to various modes has been developped by increasing the complexity of the planar structures. The results prove the benefits of the combined grid computing and hybrid approach to solve electrically large structures, by matching the size of the problem with the number of computing resources used. The study highlights the role of parallelization scheme, cluster versus grid, with respect to the size of the problem and its repartition. Moreover, a prediction model for the computing performances on grid, based on a hybrid approach that combines a historic-based prediction and an application profile-based prediction, has been developped. The predicted values are in good agreement with the measured values. The analysis of the simulation performances has allowed to extract practical rules for the estimation of the required resources for a given problem. Using all these tools, the propagation of the electromagnetic field inside a complex oversized structure such an airplane cabin, has been performed on grid and also on a supercomputer. The advantages and disadvantages of the two environments are discussed.

Orientador: Sérgio Kurokawa / Resumo: Nos sistemas de potência, o conhecimento dos parâmetros das linhas de transmissão possibilita o ajuste preciso dos sistemas de proteção, facilita a aplicação de ferramentas e técnicas de análise do sistema elétrico, permite a correta localização de faltas, assim como o monitoramento de indicadores comuns de faltas, como a temperatura e a catenária do condutor. As metodologias de estimação de parâmetros de linha de transmissão baseadas na teoria da decomposição modal são restritas a configurações de torre específicas, nas quais a matriz de transformação da linha de transmissão é conhecida. Neste trabalho apresenta-se um método para a estimação de parâmetros de linhas de transmissão genéricas em regime permanente, utilizando os fatores de correntes e tensões nos terminais da linha. Estabelece-se um sistema de equações não linear indeterminado, a partir das relações fase-modo das correntes e tensões nos terminais da linha e as matrizes de impedância e admitância da linha. Para uma linha trifásica genérica as relações fase-modo são escritas em função dos elementos da matriz transformação, os quais são desconhecidos e uma parte das incógnitas do sistema de equações. O sistema de equações é complementado com equações adicionais para ser resolvido mediante o algoritmo de Newton-Raphson e estimar os parâmetros de linha de transmissão. Foram estimados os parâmetros para uma linha de transmissão trifásica com diferente configuração de torre operando com diferentes cargas para vários co... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Accuracy in transmission lines parameters is essential in power systems since it allows precise adjustment of the protection systems, the application of tools and techniques for analysis of the electrical system, the correct identification of fault location, as well as the monitoring of fault indicators such as the temperature and the catenary of the conductor. Transmission line parameter estimation methodologies based on modal decomposition theory are restricted to specific tower configurations in which the transformation matrix of the transmission line is known. This work presents a method to estimate parameters of generic transmission lines in the steady state, using the voltage and currents phasor at the terminals of the line. A system of consistent non-linear equations is established from the phase-mode relations of these voltage and current phasors and the impedance and admittance matrices of the line. The phase-mode relations are written as a function of the elements within the transformation matrix, which are unknown and part of the variables to be estimated. The system of equations is solved using the Newton-Raphson algorithm to estimate both the transmission line parameters and the transformation matrix. The parameters were estimated for three-phase transmission lines for a particular tower configuration operating under different loads and lengths. The relative error of the estimated parameters evaluates the method’s accuracy and the influence of the line’s lumped r... (Complete abstract click electronic access below) / Doutor

L’utilisation de câbles électriques et leurs longueurs dans certains systèmes électriques ont fortement augmenté au cours des dernières années. Or, la fiabilité de ces systèmes repose en partie sur la fiabilité des réseaux électriques. On constate en pratique qu’une part non négligeable des pannes et des dysfonctionnements de ces systèmes proviennent des défauts dans les liaisons filaires et non des équipements électriques. La connaissance de ces réseaux filaires et en particulier la détection de leurs défauts est donc importante. De nombreuses méthodes ont été développées pour tester l’état des câbles. Parmi ces méthodes on peut distinguer les méthodes de réflectométrie largement utilisées et facilement embarquables. Généralement ces méthodes sont très bien adaptées pour détecter et localiser les défauts francs mais les défauts non francs sont pratiquement transparents à ces méthodes car ils ont des conséquences électriques très faibles. Pour s’affranchir de ces limitations des améliorations en termes de mesure et traitement sont nécessaires. Dans cette thèse, trois nouvelles méthodes de diagnostic filaire ont été développées pour améliorer et faciliter la détection et la localisation de tous types de défauts filaires. Chacune des ces méthodes répond à un obstacle que nous avons rencontré pendant les trois années de recherche. Un premier obstacle concerne le phénomène de dispersion du signal dans les câbles qui rend la détection des défauts et du vieillissement des câbles très difficile. Un autre obstacle lié à la détection des défauts non-francs présente un enjeu actuel majeur du diagnostic filaire car leurs signatures sont très faibles et parfois noyées dans le bruit ou masquées par la proximité d’une autre impulsion d’amplitude plus importante. Les trois méthodes sont les suivantes : – La première méthode proposée, baptisée « corrélation adaptative » fournit un nouvel algorithme pour compenser la dispersion du signal. Elle permet de mieux localiser et mieux détecter les singularités sur des câbles de n’importe quelle longueur. – La deuxième méthode proposée, baptisée TRR (en anglais Time reversal Reflectometry) est basée sur le principe de la réflectométrie et du retournement temporel. Elle permet de caractériser le vieillissement des câbles électriques. – La troisième méthode proposée, baptisée RART (Réflectométrie associée à un processus de retournement temporel) est basée sur les principes de la réflectométrie et du retournement temporel et permet d’améliorer la détection des défauts électriques liés à une dégradation de l’isolant. Ces travaux de thèse ont montré les performances et la facilité de ces méthodes visant à assurer la sureté de fonctionnement des systèmes électriques que ce soit dans des moyens de transport, un bâtiment ou même des réseaux de communication. / The use of electric cables in electrical systems has been significantly increasing over the last decades. However, the reliability of these systems is partially based on the reliability of electrical networks. Current practices show that a significant number of failures and malfunctions of these systems come from faults in wired links and not from electrical devices. Therefore, the knowledge of the state of wire networks and particularly the detection of their faults is important. Several methods have been developed to test the status of cables. Among them, reflectometry methods are widely used and easily embeddable. Generally, these methods are appropriate to detect and locate hard faults but soft faults are virtually transparent to them because this kind of fault has very low electrical consequences. Improvements in measurement and treatment are necessary to overcome the limitations of these methods. In this respect, three new methods for wire diagnosis have been studied and developed to improve and ease the detection and location of soft wire faults. Each of these methods circumvents one or more of the barriers encountered during this research’s duration. First barrier, the phenomenon of signal dispersion in cables makes the detection of faults and of cable aging difficult or imprecise. Another barrier, the detection of soft faults, represents currently a major issue of wire diagnosis because the amplitude of soft faults signatures is very small and sometimes noisy or masked by the proximity of higher pulses. The three methods can briefly described as follows : – The first method, called "adaptive correlation", provides a new algorithm to compensate signal’s dispersion. It improves fulat’s location and the detection of singularities on cables regardless their lengths. – The second method, called TRR (Time Reversal Reflectometry), is based on the principle of reflectometry and time reversal. It allows the characterization of aging of electrical cables. – The third method, called RART (Reflectrometry combined with a time reversal process), is also based on the principle of reflectometry and time reversal. It improves the detection of electrical faults related to degradation of insulation. This research illustrates the efficiency and applicability of the proposed methods. It also demonstrates the potential of the proposed methods to improve safety in operation of electrical systems whether in transport, construction, or even communication networks.

Incertezas de modelo invadem todos os estágios de uma análise de confiabilidade estrutural, desde a determinação das ações e do próprio sistema estrutural, até o processo pelo qual o efeito destas ações é avaliado. Neste trabalho, o enfoque é dado nesse último tópico, mais especificamente na avaliação das incertezas de modelo mecânico em torres metálicas treliçadas de linhas de transmissão (LT), o qual tem permanecido ignorado nas estimativas de confiabilidade até então, em parte devido a sua natureza elusiva. Logo, o problema consiste em avaliar as incertezas na predição da resposta estrutural, uma vez que todos os parâmetros que definem as ações externas e o próprio sistema são claramente definidos. A principal motivação deste trabalho partiu de um estudo conduzido pela CIGRÉ sobre torres metálicas treliçadas de LT submetidas a cargas estáticas, o qual sugere que as incertezas de modelo neste tipo de estrutura são relevantes e não podem ser desprezadas, podendo influenciar significativamente na estimativa da confiabilidade. Neste trabalho, são avaliados diferentes modelos mecânicos de torres de LT sujeitos a ações estáticas, além de modelos de torres e trechos de LT submetidos à ação dinâmica de ruptura de cabo, adotada por ser um carregamento dinâmico “bem definido”. Na análise estática, são estudados desde modelos simplificados de torres autoportantes, adotados na prática usual de projeto, até modelos mais aprimorados. A dispersão nos resultados numéricos entre os modelos é usada para quantificar as incertezas relacionadas ao modelo mecânico, e os resultados disponíveis de ensaios estáticos em protótipos são utilizados para encontrar os modelos cuja resposta mais se aproxima dos valores experimentais. A resposta dinâmica de torres metálicas treliçadas de LT submetidas à ruptura de cabo, é comparada entre vários modelos, com diferentes graus de sofisticação e detalhe. São estudados desde o modelo usual de análise e projeto de torres para este tipo de carregamento, passando por modelos relativamente simples, com uma única torre sujeita a uma carga variável no tempo, simulando o efeito da ruptura de um cabo, até modelos mais complexos de trechos de LT, os quais incluem várias torres, cabos e cadeias de isoladores. Diversas fontes de incerteza são avaliadas, considerando a influência de fatores relevantes tais como: a discretização dos elementos de cabo, as condições de contorno dos elementos de cabo das extremidades, as leis constitutivas dos elementos de barra e de cabo e o amortecimento estrutural. Por fim, são discutidas e apresentadas possíveis maneiras de considerar explicitamente a incerteza de modelo na estimativa da confiabilidade e em códigos de projeto de estruturas de linhas de transmissão. / Model uncertainties pervade all stages of a structural reliability analysis, from the description of loads and the system itself, to the process by which the effect of loads on the system is evaluated. In this study, attention is focused on the last issue, specifically in the evaluation of model uncertainties on transmission lines (TL) latticed steel towers, which has remained largely ignored in previous developments of structural reliability, in part due to its elusive nature. In essence, the problem consists of evaluating the uncertainty in response predictions, once all parameters that define the external actions and the system itself have been unequivocally prescribed. The main motivation of this thesis was a study conducted by CIGRÉ on TL latticed steel towers subjected to static loads, among other exploratory assessments, which suggests that model uncertainty is a relevant factor and cannot be disregarded, could significantly influence the outcome of reliability assessments. Herein, different mechanical models of TL self-supporting towers subjected to static loads are evaluated, besides the models of towers and TL segments submitted to dynamic load due to cable rupture, adopted by being a “well defined” loading. In the static analysis, from simplified models of self-supporting towers, like adopted in usual practice of project, to more refined models are studied. The dispersion in the numeric results among the models, together with the data of static prototype tests, are used to quantify model uncertainties. The dynamic response of latticed TL steel towers subjected to cable rupture is predicted by use of various models with different degrees of sophistication or detailing. The predictions of the various models are compared with the aim of quantifying model uncertainty. Several uncertainty sources are evaluated, considering the influence of relevant factors such as: the discretization of the cable elements, the boundary conditions of the end cable elements, the constitutive laws of cables and tower members and the structural damping. Finally, possible ways to explicitly consider model uncertainty in reliability assessments and in code formulations are discussed.

Lors de cette thèse, on a développé un banc automatisé de relevé du diagramme de rayonnement particulièrement pour des antennes millimétriques avec faible directivité. On propose trois méthodes d’alimentation. La première méthode développée a été de concevoir une nouvelle sonde ayant un accès micro-coaxial de plus de 5cm afin de réduire la zone de masquage au minimum. Associée à une configuration de type flip-chip inversée, cette méthode a permis d’avoir une réduction de la zone de masquage de 80° à 20°. La deuxième méthode a été de concevoir une liaison souple par film souple de Kapton. Cette méthode présente l’avantage de placer une plus grande partie des connexions métalliques sous un plan de masse, mais nécessite une connexion optimale à la puce. Les résultats obtenus présentent une zone de masquage pratiquement inexistante, et sont conformes à l’état de l’art. La troisième méthode SER est basée sur la mesure de l’antenne sans placer de sondes ou de connecteurs spéciaux, mais en utilisant un système à charges connues. La simulation nous montre qu'il nous manque une dynamique par ces trois charges. / In this thesis, we designed and built a new 3D test bench, particularly for low-directivity integrated antennas at millimeter-wave frequencies. We proposed three feeding techniques for the antenna under test (AUT): a probe-fed technique, a flexible-transmission-line-fed technique and a radar-cross-section (RCS) method. The probe-fed method was developed with a customized probe, which involves an elongated (50 mm) coaxial line between the probe tip and the probe body, wherein the probe body is reversed (relative to the conventional measurement configuration) so it lies below the plane of the AUT. This method reduces the range of angles that are masked from 80° (for a conventional probe setup) to 20°. The second method was developed using a flexible transmission line with a modified flip-chip connection to the AUT. This method completely eliminates the masked zone. The third method characterizes the radiation pattern using a radar cross-section (RCS) method. This method requires neither a probe system nor connectors. However the simulation results demonstrate that there is insufficient variation in the ratio of received power to incident power as the load on the AUT is varied in order to make precise measurement with conventional measurement equipment.

Made available in DSpace on 2014-06-11T19:22:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-26Bitstream added on 2014-06-13T19:28:03Z : No. of bitstreams: 1 souzajunior_nv_me_ilha.pdf: 788447 bytes, checksum: 8b9466a049a4bdb01e9292faf0c87bb0 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Sabe-se que uma linha de transmissão polifásica pode ser representada no domínio modal, por seus n modos de propagação que se comportam como sendo n linhas monofásicas independentes. Uma vez calculadas as correntes e tensões no domínio modal, as mesmas são convertidas para o domínio das fases por meio de uma matriz de transformação modal. A matriz de transformação modal é uma matriz cujos elementos são escritos em função dos parâmetros longitudinais e transversais da linha, variam em função da frequência e, geralmente, são obtidos por meio de métodos numéricos. Deste modo, diz-se que o modelo obtido é um modelo numérico de linha. Neste trabalho foi feita uma abordagem a respeito de um modelo analítico de linha de transmissão bifásica. O modelo proposto utiliza também a representação modal, mas a matriz de transformação será obtida analiticamente em função dos parâmetros da linha. Deste modo, foi possível obter, analiticamente, relações entre as correntes e tensões de fase da linha baseando-se unicamente nos parâmetros longitudinais e transversais da mesma / It is know that polyphase transmission line can be represented in the modal domain its n propagation modes that behave as n independent single-phase lines. Once calculated the currents and voltages in the modal domain, they are converted into the realm of the phases by means of a modal transformation matrix. The modal transformation matrix is a matrix whose elements re written against the parameters of longitudinal and cross the and they are usually obtained by numerical methods. In this paper an approach was made on an analytical model of two-phase transmission line. The proposed model uses the modal representation, but the transmission matrix obtained analytical in terms of line parameters. The development of the analytical model will be based on the modal model. Thus, initially will be obtained analytically, a modal matrix decomposition that allows to calculate analytically the eigenvalues of the product [Z][Y] line. Once obtained the eigenvalues it possible to abtain the modes of propagation and characteristic impedance of the line modes. Then, using the solutions algebraic differential equation of a single-phase line, we abtain the equations of currents and voltages of each of modes of spread of the row. In a final step, the equations of modal currents and voltages are converted into the realm of the phases, resulting in algebraic equations that can calculate the currents and phase voltages of the line in the frequency domain

Made available in DSpace on 2014-06-11T19:22:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-28Bitstream added on 2014-06-13T20:49:17Z : No. of bitstreams: 1 silvafilho_eb_me_ilha.pdf: 1002165 bytes, checksum: 7b47e608bd37c2b8a03cccc84f847230 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho analisa a aplicação em linhas de transmissão do método dos elementos de contorno para cálculo de potencial e campo elétrico, com um enfoque em eletrostática. O método dos elementos de contorno baseia-se numa formulação integral que elimina a discretização do domínio, restando apenas o contorno, permitindo o cálculo do potencial e do campo elétrico no contorno e na região estudada. O trabalho configura-se como uma revisão sobre eletrostática, ressaltando as equações de Laplace e Poisson, que serão utilizadas para encontrar as equações integrais do contorno. Há também vários tópicos relacionados ao campo elétrico de linhas de transmissão, bem como, ás normas brasileiras e recomendações internacionais que devem ser utilizadas no projeto de linhas de transmissão. O método dos elementos de contorno utiliza tais equações integrais para encontrar o potencial e o campo no contorno, e após conhecidos o potencial e o campo no contorno, pode-se aplicar o método em todo o domínio, obtendo o potencial e o campo. Para isso, apenas o contorno do domínio de interesse deve ser discretizado, o que trás uma enorme vantagem sobre os métodos que utilizam formulação diferencial. Neste trabalho, serão descritas as principais características do código computacional desenvolvido e suas sub-rotinas mais importantes. Para validar o programa, os resultados serão comparados com aqueles calculados por um procedimento analítico, sendo mostrada a eficiência da discretização do solo. São apresentados os resultados obtidos da análise do campo elétrico gerado por algumas silhuetas de linhas de transmissão. Os valores do campo elétrico gerado por estruturas compactas são comparados com estruturas convencionais e estruturas reduzidas (semi-compactas), também serão comparados os valores do gradiente de potencial na superfície dos condutores e suas capacitâncias equivalentes. / This paper analyses the application in transmission lines of the Boundary Element Method (BEM) of the calculation of potential and electric field, with a focus on electrostatic. The Boundary Element Method is based on an integral formulation that eliminates the discretisation of the domain, remaining only the contour, allowing the calculation of the potential and the electric field in the contour and in the region studied. The work is configured as revision on electrostatic, underscoring the equations of Laplace and Poisson, which will be used to find the integral equations of the contour. There are also several topics related to the electric field of transmission lines, as well as to the standards Brazilian and international recommendations to be used in the design of transmission lines. The Boundary Element Method uses such integral equations for finding the potential and electric field in the contour, and after having known the potential and electric field in the contour, the BEM can be applied in the whole domain, and getting the potential and electric field. Therefore, only the contours of the domain of interest should just be discretized, which backward an enormous advantage on the methods that use formulation differential. This paper will describe the main characteristics of computer code developed and their sub-routines more important. To validate the program, the results will be compared with those calculated by an analytic procedure, being shown the efficiency of discretisation of the soil. The results obtained from analysis of the electric field generated by some silhouettes of transmission lines are presented. The values of the electric field generated by compact structures are compared with conventional structures and reduced structures, also will be compared the values of the gradient of potential on the surface of the conductors and their equivalents capacitances.

Made available in DSpace on 2014-12-17T14:55:12Z (GMT). No. of bitstreams: 1 ManoelBLA.pdf: 2395577 bytes, checksum: 6394225c6ebbbdad59d4fa162aa97882 (MD5) Previous issue date: 2008-11-19 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This paper presents a theoretical and numerical analysis of the parameters of a rectangular microstrip antenna with metamaterial substrate. The metamaterial (MTM) theory was applied along with Transverse Transmission Line (LTT) method to characterize substrate quantities and obtain the general equations of the electromagnetic fields. A study on metamaterial theory was conducted to obtain the constructive parameters, which were characterized through permittivity and permeability tensors to arrive at a set of electromagnetic equations. Electromagnetic principes are used to obtained parameters such as complex resonance frequency, bandwidth and radiation pattern were then obtained. Different metamaterial and antenna configurations were simulated to miniaturize them physically and increase their bandwidth, the results of which are shown through graphics. The theoretical computational analysis of this work proved to be accurate when compared to other studies, and may be used for other metamaterial devices. Conclusions and suggestions for future work are also proposed / Este trabalho apresenta a an?lise te?rica e num?rica dos par?metros de uma antena de microfita tipo patch retangular sobre substrato metamaterial. Para isso, ? aplicada a teoria de metamateriais - MTM, em conjunto com o m?todo da Linha de Transmiss?o Transversa - LTT, para a caracteriza??o das grandezas do substrato e obten??o das equa??es gerais dos campos eletromagn?ticos. ? realizado um estudo acerca da teoria de metamateriais com o intuito de obter seus par?metros construtivos, os mesmos s?o caracterizados atrav?s de tensores permissividade e permeabilidade. Essa teoria ? aplicada ao m?todo da Linha de Transmiss?o Transversa chegando-se ?s equa??es gerais para os campos eletromagn?ticos da antena. Em seguida s?o utilizados princ?pios da teoria eletromagn?tica para obter-se caracter?sticas como: freq??ncia de resson?ncia complexa, diagramas de radia??o e largura de banda. S?o simulados diferentes configura??es de metamateriais e antenas com o intuito de miniaturizar as dimens?es f?sicas e aumentar a largura de banda das mesmas, os resultados s?o apresentados atrav?s de gr?ficos. A an?lise te?rica computacional deste trabalho se mostra precisa, em compara??o a outros, podendo ser empregado em dispositivos que utilizem metamateriais como substratos. Ao final s?o apresentadas conclus?es e sugest?es para trabalhos futuros