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Previous issue date: 2013-07-25 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq / Neste trabalho, as propriedades de auto-similaridade dos fractais s?o exploradas para o desenvolvimento de superf?cies seletivas de frequ?ncia (Frequency Selectives Surfaces - FSS) com v?rias bandas de rejei??o. Em particular, s?o considerados fractais de Gosper, na defini??o dos formatos dos elementos das FSS. Por conta da dificuldade de impress?o de detalhes dos elementos das FSS, s?o considerados apenas elementos pr?-fractais, com at? tr?s itera??es fractais. As simula??es foram realizadas com o uso do programa comercial Ansoft Designer. Para fins de valida??o de resultados, foram constru?dos v?rios prot?tipos de FSS com elementos pr?-fractais. No processo de fabrica??o, os formatos dos elementos pr?-fractais foram desenhados com aux?lio do programa Corel Draw. Os prot?tipos constru?dos foram medidos atrav?s de um analisador de redes vetorial (modelo N3250A, da Agilent Technologies). A utiliza??o de elementos pr?-fractais nas estruturas de FSS consideradas, permitiu verificar que o aumento do n?vel fractal possibilita a redu??o do tamanho dos elementos, por?m reduz a largura de banda das mesmas. Neste sentido, ? tamb?m investigado o efeito produzido pelo cascateamento de estruturas de FSS na largura de banda. Foi observado que o uso de estruturas cascateadas, al?m de aumentar a largura de banda, permitiu, em alguns casos, a obten??o de at? respostas em frequ?ncia com tr?s bandas de opera??o entre 6 GHz e 15 GHz. / The fractal self-similarity property is studied to develop frequency selective surfaces (FSS)
with several rejection bands. Particularly, Gosper fractal curves are used to define the shapes
of the FSS elements. Due to the difficulty of making the FSS element details, the analysis is
developed for elements with up to three fractal levels. The simulation was carried out using
Ansoft Designer software. For results validation, several FSS prototypes with fractal elements
were fabricated. In the fabrication process, fractals elements were designed using computer
aided design (CAD) tools. The prototypes were measured using a network analyzer (N3250A
model, Agilent Technologies). Matlab software was used to generate compare measured and
simulated results. The use of fractal elements in the FSS structures showed that the use of
high fractal levels can reduce the size of the elements, at the same time as decreases the
bandwidth. We also investigated the effect produced by cascading FSS structures. The
considered cascaded structures are composed of two FSSs separated by a dielectric layer,
which distance is varied to determine the effect produced on the bandwidth of the coupled
geometry. Particularly, two FSS structures were coupled through dielectric layers of air and
fiberglass. For comparison of results, we designed, fabricated and measured several
prototypes of FSS on isolated and coupled structures. Agreement was observed between
simulated and measured results. It was also observed that the use of cascaded FSS structures
increases the FSSs bandwidths and, in particular cases, the number of resonant frequencies, in
the considered frequency range. In future works, we will investigate the effects of using
different types of fractal elements, in isolated, multilayer and coupled FSS structures for
applications on planar filters, high-gain microstrip antennas and microwave absorbers
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/19472 |
| Date | 25 July 2013 |
| Creators | Santos, Albanisa Felipe dos |
| Contributors | 04401565487, http://lattes.cnpq.br/4159638862269940, D'Assun??o J?nior, Adaildo Gomes, 00980645417, http://lattes.cnpq.br/7359899329008024, Siqueira, Gl?ucio Lima, 16326504600, http://lattes.cnpq.br/3820441792646415, Silva, Paulo Henrique da Fonseca, 98196294700, http://lattes.cnpq.br/0656625630248917, D'Assun??o, Adaildo Gomes |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM ENGENHARIA EL?TRICA E DE COMPUTA??O, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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