yes / A compact dual U-shaped slot PIFA antenna with Electromagnetic Bandgap (EBG) material on a relatively low dielectric constant substrate is presented. Periodic structures have found to reduce mutual coupling and decrease the separation of antenna and ground plane. A design with EGB material suitable for a small terminal mobile handset operating at 2.4 GHz was studied. Simulated and measured scattering parameters are compared for U-shaped slot PIFA antenna with and without EBG structures. An evaluation of MIMO antennas is presented, with analysis of the mutual coupling, correlation coefficient, total active reflection coefficient (TARC), channel capacity and capacity loss. The proposed antenna meets the requirements for practical application within a mobile handset. / Electronics and Telecommunications

abstract: Flexibility, reconfigurability and wearability technologies for antenna designs are presented, investigated and merged in this work. Prior to the design of these radiating elements, a study is conducted on several flexible substrates and how to fabricate flexible devices. Furthermore, the integration of active devices into the flexible substrates is also investigated. A new approach of designing inkjet-printed flexible reconfigurable antennas, based on the concept of printed slot elements, is proposed. An alternate technique to reconfigure the folded slot antenna is also reported. The proposed radiator works for both Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications. The flexible reconfigurable antenna is also redesigned to resonate at both (2.4/5.2 GHz) for WLAN devices and its Multiple-Input Multiple-Output (MIMO) configuration is reported. Two orthogonal elements are used to form the MIMO antenna system for better isolation. The wearability of the proposed flexible reconfigurable radiator is also discussed. Since wearable antennas operate close to the human body, which is considered as a lossy tissue, an isolation between the radiating elements and human body is required to improve the radiation characteristics and to reduce the Specific Absorption Rate (SAR). The proposed antenna is redesigned on an Artificial Magnetic Conductor (AMC) surface that also functions as a ground plane to isolate the radiator from the human body. To examine its performance as a body-worn device, it is measured at different positions on the human body. Furthermore, simulations show that the SAR level is reduced when using the AMC surface. The proposed wearable antenna works for both Wireless Body Area Network (WBAN) and WiMAX body-worn wireless devices. Electromagnetic bandgap (EBG) structures are used to suppress surface wave propagation in printed antennas. However, due to the presence of vias, not all of them can be utilized in flexible radiators. Thus, a Perforated High Impedance Surface (PHIS) is proposed which suppresses the surface waves without the need of vias, and it also serves as a ground plane for flexible antennas. The surface wave suppression and the antenna applications of the proposed PHIS surface are discussed. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

Submitted by camilla martins (camillasmmartins@gmail.com) on 2017-04-27T13:05:18Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_AnaliseTeoricaFiltros.pdf: 4789588 bytes, checksum: 8e8c2066525cc43ae730dd29a6cdff9d (MD5) / Approved for entry into archive by Edisangela Bastos (edisangela@ufpa.br) on 2017-05-04T12:38:55Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_AnaliseTeoricaFiltros.pdf: 4789588 bytes, checksum: 8e8c2066525cc43ae730dd29a6cdff9d (MD5) / Made available in DSpace on 2017-05-04T12:38:55Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_AnaliseTeoricaFiltros.pdf: 4789588 bytes, checksum: 8e8c2066525cc43ae730dd29a6cdff9d (MD5) Previous issue date: 2016-11-25 / Este trabalho apresenta simulações de filtros rejeita-faixa de micro-ondas utilizando estruturas Electromagnetic Bandgap (EBG). Na estrutura de filtro são feitos furos no plano terra e posteriormente esses furos terão o seu diâmetro alterado visando melhorar a qualidade da banda de rejeição e a obtenção de duas bandas de rejeição. Em comparação com filtros convencionais, filtros com estruturas EBG tem melhores características de banda de rejeição na faixa de micro-ondas As referidas simulações foram feitas com o software comercial ANSYS HFSS. Uma estrutura de filtro utilizando guias de ondas fotônicos também é modelada e simulada utilizando o software comercial Comsol. Os efeitos dos parâmetros físicos da estrutura em relação as característica de filtragem são estudados em ambos os filtros. Os resultados do procedimento de criação e de simulação são descritos e possíveis aplicações dessas estruturas de filtro são discutidas neste trabalho. A faixa de rejeição particularmente ampla é alcançada pelos circuitos apresentados neste trabalho bem como duas bandas de rejeição. / This paper presents simulations of a band-stop filter using microwave Electromagnetic Bandgap structures (EBG). In the filter structure are made holes in the ground plane and these holes will subsequently changed its diameter to improve the rejection band of the quality and obtaining two rejection bands. Compared with conventional filters, filters with EBG structures have better rejection bandwidth characteristics in the microwave band. These simulations were performed with commercial software ANSYS HFSS. A filter structure using photonic waveguides is also modeled and simulated using commercial software Comsol. The effects of the physical parameters of the structure in relation to the filter characteristic are studied in both filters. The results of the creation and simulation procedure are described and possible applications of these filter structures are discussed in this paper. The particularly wide stopband is achieved by the circuits presented in this paper as well as two rejection bands.