Aplicação de curvas fractais em elementos convolucionados para o projeto de FSS miniaturizada e com estabilidade angular

Abstract

Frequency selective surfaces (FSS) have been used in telecommunications for various purposes ranging from the manufacture of hyper-gain antennas and subrefletors to its use as blocking signals in prisons. The possibility of coupling them to microstrip antennas and waveguides, and its enormous potential to cope with the arising problem of interference within communication systems make them even more attractive to the market. The aim of this study is to describe and analyze a FSS multiband behavior, with independent of polarization and angular stability, which is a result of combining different miniaturization techniques, such as fractalization and the use of convoluted elements, so as to make it more compact, lightweight and efficient. To do so, in this thesis it is previously conducted a bibliographic study of the FSS and monofractal geometry. This work also describes the main miniaturization techniques available in the literature, revealing the effects and benefits of each one with respect to the response of the structure. Five FSS models are chosen and each one is properly analyzed. For the simulated results it’s used the commercial software Ansoft Designer, which does an analysis of the electromagnetic behavior of the FSS with the Method of Moments (MoM). The measured results, in turn, are obtained with a network vector analyzer, model Agilent N5230A, and they show a good agreement with the simulated values. It is found that with application of combined miniaturization techniques, it is possible to obtain a miniaturization factor of up to 79:3% in the size of the FSS.