Made available in DSpace on 2014-12-17T14:56:20Z (GMT). No. of bitstreams: 1 FranciscoCGSS_Capa_ate_pag41.pdf: 9091246 bytes, checksum: 6f81612f5fd4ab8558666746d9be5489 (MD5) Previous issue date: 2014-06-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Frequency selective surfaces (Frequency Selective Surface - FSS) are often used in various applications in telecommunications. Some of these applications may require that these structures have response with multiple resonance bands. Other applications require that the FSS response have large frequency range, to meet the necessary requirements. FSS to design with these features there are numerous techniques cited in the scientific literature. Thus, the purpose of this paper is to examine some common techniques such as: Overlap of FSS; Elements combined; Elements Elements convolucionados and fractals. And designing multiband FSS and / or broadband selecting simple ways in terms of construction and occupy the smallest possible space, aiming at practical applications. Given these requirements, three projects FSS were performed: a technology applied to IEEE 802.11 a/b/g/n and two projects for application in UWB. In project development, commercial software Ansoft DesignerTM and experimental results were satisfactory was used / Superf?cies seletivas em frequ?ncia (Frequency Selective Surface - FSS) s?o usadas frequentemente em diversas aplica??es em telecomunica??es. Algumas dessas aplica??es podem exigir que essas estruturas tenham resposta com m?ltiplas bandas de resson?ncia. Outras aplica??es exigem que as FSS tenham resposta em faixa larga de frequ?ncia, para atender aos requisitos necess?rios. Para projetar uma FSS com essas caracter?sticas existem in?meras t?cnicas citadas na literatura cient?fica. Assim, o prop?sito deste trabalho ? analisar algumas t?cnicas utilizadas tais como: Sobreposi??o de FSS; Elementos combinados; Elementos convolucionados e Elementos fractais. E projetar FSS multibanda e/ou banda larga selecionando maneiras simples em termos de constru??o e que ocupem o menor espa?o poss?vel, visando aplica??es pr?ticas. Tendo em vista estes requisitos, foram realizados tr?s projetos de FSS: um aplicado a tecnologia IEEE 802.11 a/b/g/n e dois projetos para aplica??o em UWB. No desenvolvimento dos projetos, foi utilizado o software comercial Ansoft DesignerTM e os resultados experimentais se mostraram satisfat?rios

The recent progress in electronics and communication technologies has driven the unprecedented demand for multi-functional wireless communication in most single wireless devices. However, employing the limited spectrum effectively on communication equipment poses a key design challenge, as most antennas often suffer from bandwidth limitations and restricted frequency rarge. Onekey approach to overcome this problem without significantly affecting the antenna size is to apply antenna tuneability and reconfigurability. This is achieved by electronically changing some properties of the antenna usually by loading the reactive loading of the resonator by means of active electronic elements including varactor diode or PIN diode with extra circuitry. The main objective of this research is to design and investigate low-profile antennas for heterogeneous wireless systems using the antenna reconfigurability concept through tuning and/or using the MIMO antenna techniques. The research focuses on antenna design and implementation to cover various wireless standards and applications within the electromagnetic spectrum including UMTS (1.92-2.17 GHz), Cognitive Radio such as WLAN and WiMAX (2.4GHz), Wi-Fi (5.2GHz), 5G (600MHz - 6GHz) and MBAN applications. A family of compact microstrip printed reconfigurable antennas for various cognitive radio applications is presented. Effects of various slots on the antenna performance are also investigated, and the final version was reconfigured across a broad frequency range (1.5 - 2.4 GHz) Furthermore, four new variants of the miniaturised hexagonal-shaped monopole printed antennas for different UWB applications are proposed. Prototypes of the four versions are fabricated and compared to establish their results. Two reconfigurable rejection bands are introduced to avoid anticipated interference with other systems working within the UWB range. Finally, a novel low-profile four-element MIMO antenna was designed and fabricated to operate at the 2.4 GHz ISM band. both measurements and simulation results revealed strong agreement. Furthermore, the designed antenna was also tested on human tissues, with acceptable results when compared to its performance in free space. it is proved to be a good fit for wireless, mobile communications, medical systems and WBAN applications. / Libyan Ministry of Higher Education. / Subtitle: Simulation and Measurement of Reconfigurable Antennas for Cognitive Radio, UWB Applications, Investigation of Antenna Gain and Efficiency, Frequency Tuneable Range, Antenna Radiation Performance and Antenna Design Optimization using Parametric Studies as well as using MIMO antenna for wireless body area networks