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dc.contributor.advisor Smith, David R en_US
dc.contributor.author Sajuyigbe, Adesoji en_US
dc.date.accessioned 2010-05-10T20:17:20Z
dc.date.available 2010-05-10T20:17:20Z
dc.date.issued 2010 en_US
dc.identifier.uri http://hdl.handle.net/10161/2450
dc.description Dissertation en_US
dc.description.abstract <p>This dissertation examines the use of artificial structured materials -- known as metamaterials -- in two antenna applications in which conventional dielectric materials are otherwise used. In the first application, the use of metamaterials to improve the impedance matching of planar phased array antennas over a broad range of scan angles is explored. A phased array antenna is composed of an array of antenna elements and enables long-distance signal propagation by directional radiation. The direction of signal propagation is defined as the scan angle. The power transmission ratio of a phased array is the ratio of the radiated power to the input power, and depends on the scan angle. The variation in the power transmission ratio is due to the different mutual coupling contributions between antenna elements at different scan angles. An optimized stack of dielectric layers, known as a wide-angle impedance matching layer (WAIM), is used to optimize the power transmission ratio profile over a broad range of scan angles. In this work, the use of metamaterials to design anisotropic WAIMs with access to a larger range of constitutive parameters -- including magnetic permeability -- to offer an improved power transmission ratio at a broad range of scan angles is investigated. </p> <p>In the second antenna application, a strategy to create maximally transmissive and minimally reflective electromagnetic radome materials using embedded metamaterial inclusions is introduced. A radome is a covering used to protect an antenna from weather elements or provide structural function such as the prevention of aerodynamic drag. A radome should be made from a fully transparent and non-refractive material so that radiated fields from and to the enclosed antenna are not disrupted. The aim of this research was to demonstrate that embedded metamaterial inclusions can be used to isotropically adjust the dielectric properties of a composite material to a desired value. This strategy may lead to the creation of a structural material with electromagnetic properties close to air, thus reducing the detrimental scattering effects often associated with conventional radome materials.</p> <p>Chapter 1 introduces the concept of metamaterials and discusses the use of subwavelength metallic structures to artificially engineer constitutive parameters such as permeability of permittivity. In Chapter 2, the analytical formulations that enable the characterization of the transmission performance of a planar phased array covered with anisotropic impedance matching layers are developed. Chapter 3 discusses the design rules that must govern the design parameters of anisotropic WAIMs realizable using metamaterials, and also presents examples of anisotropic impedance matching layers that provide a maximum power transmission ratio for most scan angles. In addition, numerical and experimental results on a metamaterial placed over a phased array are presented. In Chapter 4, the feasibility of using metamaterials to realize a minimally transparent and fully transmissive radome material is numerically investigated. In Chapter 5, experimental results that corroborate earlier numerical simulation results are analyzed.</p> en_US
dc.format.extent 24475834 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject Engineering, Electronics and Electrical en_US
dc.subject Physics, Electricity and Magnetism en_US
dc.subject Metamaterials en_US
dc.subject Phased Array Antennas en_US
dc.subject Wide-angle impedance matching en_US
dc.title Electromagnetic Metamaterials for Antenna Applications en_US
dc.type Dissertation en_US
dc.department Electrical and Computer Engineering en_US
duke.embargo.months 6 en_US
dc.date.accessible 2010-05-18T05:00:14Z

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