Contribuição ao estudo de metodos numericos em eletromagnetismo : o metodo TLM em duas dimensões

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro TecnologicoO método de modelagem numérica denominado TLM (Transmission Linc Modeling) aplicado à análise de problemas bidimensionais, é o principal assunto deste trabalho. Inicialmente, mostra-se os conceitos da teoria de linhas de transmissão e o princípio de Huygens, pois eles são a base para o desenvolvimento do método TLM. A seguir, os princípios do método de Modelagem por Linhas de Transmissão em Duas Dimensões (TLM-2D) são apresentados. Finalmente, um conjunto de aplicações em microondas é desenvolvido, utilizando-se códigos computacionais baseados no TLM-2D e escritos em ForTran 90, a fim de validar o estudo. Abstract : The numerical modeling method, called 2D - TLM (Bidimensional Transmission Line Modeling) applied to the analysis of 2D electromagnetics problems, is the main topics of this work. Initially, the concepts of the Transmission - Line Theory and Huygens principle are presented, because they are the basis of the development of TLM method. The principles of 2D Transmission - Line Modeling method are presented. Finally, a set of microwave applications is developed, using computacional codes based on 2D - TLM and written in ForTran - 90, in order to validate the study

The use of genetic algorithms to maximize the performance of a partially lined screened room

This paper shows that it is possible to use genetic algorithms to optimize the layout of ferrite tile absorber in a partially lined screened enclosure to produce a "best" performance. The enclosure and absorber are modeled using TLM modeling techniques and the performance is determined by comparison with theoretical normalized site attenuation of free space. The results show that it is possible to cover just 80% of the surface of the enclosure with ferrite absorber and obtain a response which is within +/-4 dB of the free space response between 40 and 200 MHz

Determination of Spectral Focusing Features of a Metamaterial Slab

The realization of flat superlenses is a major application area of metamaterials. A slab of double negative (DNG) material is capable of imaging with a resolution below the diffraction limit. The focusing quality depends primarily on the amount by which the original spectrum of the source is restored behind the lens. Even a small deviation from the ideal case limits the spectrum of the transmitted field, which may result in a significant degradation of the focusing quality. In this work we determine the width of the transmitted spectrum as a function of the configuration parameters and establish a relation between the spectrum width and the imaging quality. Restrictions imposed on the focusing characteristics and difficulties arising in full wave simulations will be pointed out

3D Simulation of Partial Discharge in High Voltage Power Networks

Open accessPartial discharge (PD) events arise inside power cables due to defects of cable’s insulation material, characterized by a lower electrical breakdown strength than the surrounding dielectric material. These electrical discharges cause signals to propagate along the cable, manifesting as noise phenomena. More significantly, they contribute to insulation degradation and can produce a disruptive effect with a consequent interruption of power network operation. PD events are, therefore, one of the best ‘early warning’ indicators of insulation degradation and, for this reason, the modeling and studying of such phenomena, together with the development of on-line PDs location methods, are important topics for network integrity assessment, and to define methods to improve the power networks’ Electricity Security. This paper presents a 3D model of PD events inside a void in epoxy-resin insulation cables for High Voltage (HV) power networks. The 3D model has been developed using the High Frequency (HF) Solver of CST Studio Suite® software. PD events of a few µs duration have been modelled and analyzed. The PD behavior has been investigated using varying electrical stress. A first study of the PD signal propagation in a power network is described

Some Key Developments in Computational Electromagnetics and their Attribution

Key developments in computational electromagnetics are proposed. Historical highlights are summarized concentrating on the two main approaches of differential and integral methods. This is seen as timely as a retrospective analysis is needed to minimize duplication and to help settle questions of attribution

Circuital and Numerical Models for Calculation of Shielding Effectiveness of Enclosure with Apertures and Monitoring Dipole Antenna Inside

In this paper, circuital and numerical models of metal In this paper, circuital and numerical models of metal enclosure with apertures are considered for the purpose of accurate shielding effectiveness calculation. An improved circuital model is presented to account for the presence of receiving dipole antenna which is often used in practice to measure the level of electromagnetic field at selected points inside the enclosure. Receiving antenna of finite dimensions could significantly change the EM field distribution inside the enclosure and thus affect the results for SE. TLM method incorporating wire node is used to create a numerical model. Both models are compared in terms of their ability to account for receiving antenna impact on shielding effectiveness of rectangular enclosure with aperture. In addition, comparison of both models is carried out for the case when an array of apertures with different aperture separation is present on one of the enclosure walls whereby the numerical TLM model is additionally enhanced with compact air-vent model

Improved determination of Q-factor and resonant frequency by a quadratic curve-fitting method

The Q-factor and peak frequency of resonant phenomena give useful information about the propagation and storage of energy in an electronic system and therefore its electromagnetic compatibility performance. However, the calculation of Q by linear interpolation of a discrete frequency response to obtain the half-power bandwidth can give inaccurate results, particularly if the data are noisy or the frequency resolution is low. We describe a more accurate method that makes use of the Lorentzian shape of the resonant peaks and involves fitting a second-order polynomial to the reciprocal power plotted against angular frequency. We demonstrate that this new method requires less than one quarter the number of frequency points as the linear method to give comparable accuracy in Q. The new method also gives comparable accuracy for signal-to-noise ratios that are approximately 8 dB greater. It is also more accurate for determination of peak frequency. Examples are given both from measured frequency responses and from simulated data obtained by the transmission line matrix method