Zugl.: Kaiserslautern, Techn. Univ., Diss., 2009

No description available.

Yes / This paper presents a novel 2D meta-surface wall to increase the isolation between microstrip patch radiators in an antenna array that is operating in the teraherz (THz) band of 139–141 GHz for applications including communications, medical and security screening systems. The metasurface unit-cell comprises conjoined twin ‘Y-shape’ microstrip structures, which are inter-digitally interleaved together to create the meta-surface wall. The proposed meta-surface wall is free of via holes and defected ground-plane hence easing its fabrication. The meta-surface wall is inserted tightly between the radiating elements to reduce surface wave mutual coupling. For best isolation performance the wall is oriented orthogonal to the patch antennas. The antenna array exhibits a gain of 9.0 dBi with high isolation level of less than −63 dB between transmit and receive antennas in the specified THz-band. The proposed technique achieves mutual coupling suppression of more than 10 dB over a much wider frequency bandwidth (2 GHz) than achieved to date. With the proposed technique the edge-to-edge gap between the transmit and receive patch antennas can be reduced to 2.5 mm. Dimensions of the transmit and receive patch antennas are 5 × 5 mm2 with ground-plane size of 9 × 4.25 mm2 when being constructed on a conventional lossy substrate with thickness of 1.6 mm. / H2020-MSCA-ITN-2016 SECRET-722424 and UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1

Yes / In this paper, a conical horn antenna has been designed for Ultra-Wideband ap-plications by loading its section with a metamaterial. The work aims first to compare results obtained by the wavelet-moment method to a simulation performed using HFSS. Secondly the conical horn is loaded with a very thin layer of metamaterial to enhance the radiation pattern and the bandwidth performance of the conical horn antenna and reduce the size of the antenna. The operating bandwidth of the proposed antenna is in the range of 10{13 GHz. The results obtained from HFSS and moment method are in good agreement. / Electronics and Telecommunications

<p>As research in electromagnetics has expanded, it has given rise to the examination of metamaterials, which possess nontrivial electromagnetic material properties such as engineered permittivity and permeability. Aside from their application in the microwave industry, metamaterials have been associated with novel phenomena since their invention, including sub-wavelength focusing in negative refractive index slabs, evanescent wave amplification in negative index media, and invisibility cloaking and its demonstration at microwave frequency with controlled material properties in space.</p><p>Effective medium theory plays a key role in the development and application of metamaterials, simplifying the electromagnetic analysis of complex engineered metamaterial composites. Any metamaterial composite can be treated as a homogeneous or inhomogeneous medium, while every unit structure in the composite is represented by its permittivity and permeability tensor. Hence, studying an electromagnetic wave's interaction with complex composites is equivalent to studying the interaction between the wave and an artificial material.</p><p>This dissertation first examines the application of a magnetic metamaterial lens in wireless power transfer (WPT) technology, which is proposed to enhance the mutual coupling between two magnetic dipoles in the system. I examine and investigate the boundary effect in the finite sized magnetic metamaterial lens using a numerical simulator. I propose to implement an anisotropic and indefinite lens in a WPT system to simplify the lens design and relax the lens dimension requirements. The numerical results agree with the analytical model proposed by Smith et al. in 2011, where lenses are assumed to be infinitely large.</p><p>By manipulating the microwave properties of a magnetic metamaterial, the nonlinear properties come into the scope of this research. I chose split-ring resonators (SRR) loaded with varactors to develop nonlinear metamaterials. Analogous to linear metamaterials, I developed a nonlinear effective medium model to characterize nonlinear processes in microwave nonlinear metamaterials. I proposed both experimental and numerical methods here for the first time to quantify nonlinear metamaterials' effective properties. I experimentally studied three nonlinear processes: power-dependent frequency tuning, second harmonic generation, and three-wave mixing. Analytical results based on the effective medium model agree with the experimental results under the low power excitation assumption and non-depleted pump approximation. To overcome the low power assumption in the effective medium model for nonlinear metamaterials, I introduced general circuit oscillation models for varactor/diode-loaded microwave metamaterial structures, which provides a qualitative prediction of microwave nonlinear metamaterials' responses at relatively high power levels when the effective medium model no longer fits.</p><p>In addition to 1D nonlinear processes, this dissertation also introduces the first 2D microwave nonlinear field mapping apparatus, which is capable of simultaneously capturing both the magnitude and phase of generated harmonic signals from nonlinear metamaterial mediums. I designed a C-band varactor loaded SRR that is matched to the frequency and space limitation of the 2D mapper. The nonlinear field generation and scattering properties from both a single nonlinear element and a nonlinear metamaterial medium composite are experimentally captured in this 2D mapper, and the results qualitatively agree with numerical results based on the effective medium model.</p> / Dissertation

Orientador: Luiz Carlos Kretly / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-19T12:48:04Z (GMT). No. of bitstreams: 1 Araujo_HumbertoXavierde_D.pdf: 7050651 bytes, checksum: 1d22c38822d1b7ff3ee74974b2d874b9 (MD5) Previous issue date: 2012 / Resumo: Este trabalho apresenta a análise detalhada, simulações numéricas completas e os procedimentos para o projeto e a implementação de uma câmara GTEM -GigaHertz Transverse Electromagnetic- para análise de pré-conformidade em circuitos e sistemas eletrônicos. O sistema construído é capaz de realizar testes de EMC - Electromagnetic Compatibility, tanto de interferência - EMI quanto de susceptibilidade - EMS, na faixa de freqüência de 500 MHz - 18 GHz. O projeto apresenta uma inovação ao introduzir estruturas metamateriais na câmara tornando-a mais flexível na determinação da freqüência e níveis de RF e Microondas de teste. Os detalhes do projeto, simulações, a tecnologia de fabricação e medidas de validação da GTEM são descritos neste trabalho / Abstract: In this work it is shown a detailed analysis, complete numerical simulations and the guidelines for the design and fabrication of a GTEM - GigaHertz Transverse Electromagnetic chamber, for pre-compliance tests of integrated circuits and electronic boards. With the built structure electromagnetic tests - EMC, including electromagnetic interference - EMI and immunity becomes feasible, on 500 MHz - 18 GHz frequency range. Besides that, an innovative concept is shown with the use of metamaterial technology applied to the GTEM chamber in order to make it more flexible in terms of frequency range. The design, simulation and fabrication strategy are clearly described along throughout this work / Doutorado / Eletrônica, Microeletrônica e Optoeletrônica / Doutor em Engenharia Elétrica

This project set out to determine, by experimentation, what changes could be made to the material properties of paper-based strips by making different patterns of incisions. The purpose of the project was to evaluate the possibilities of paper-based strips as tourniquets in clinical use for venepuncture, in which a hypodermic needle is inserted into a vein. A tourniquet is required, at a site closer to the heart than where the needle is inserted, to exert a pressure small enough to allowblood to continue being pumped through the arteries, but large enough to stop blood flowing backthrough the veins. In this way the veins become visible and enable a needle to be inserted into one of them. The paper-based strips were each 50mm by 27mm, and their properties to be examined  were the tearing strength and the extension under a range of forces. Thirty one patterns were tested, four times each. This project has aimed to use force/extension graphs to assess different pattern types for their potential use as tourniquets during venepuncture procedures. / I det här arbetet undersöktes hur pappersremsors egenskaper förändras med olika utskurna mönster. Syftet var att ta fram och utvärdera en experimentell testmetod för att särskilja och utvärdera funktionen hos pappersremsorna med tillhörande mönster. Remsorna är tänkta användas som stasband när man ska ta blodprov i vården. Stasbandet ska ansätta ett trycktillräckligt lågt för att tillåta blodgenomströmning i artärer men tillräckligt högt för att stoppa blodgenomströmning i venerna. Om detta uppfylls blir venerna synliga och det blir lättare att sticka nålen i en ven, som annars kan vara svår att se. Remsorna, med area 128 x 27 mm2 där 50x 27 mm2 är täckt med mönster, utvärderades med avseende på sträckgräns och töjning vid olika laster. Trettioett mönster testades, varje prov upprepades fyra gånger. Resultaten visas i krafttöjningsdiagram. Den framtagana testmetoden kan användas som en första screening av olikamönster i pappersremsor för att studera hur de kan användas som stasband.

Free-space imaging with a resolution beyond that dictated by the classical diffraction limit may be achieved with a `Veselago-Pendry' superlens made from a metamaterial possessing a number of specific properties, including a negative refractive index (NRI). Although a planar NRI transmission-line (NRI-TL) metamaterial based on the periodic lumped loading of a host TL network has successfully verified the phenomenon of superlensing in a 2D microstrip environment, a true Veselago-Pendry superlens capable of interacting with and manipulating fields in free space remained elusive, largely due to the difficulty of meeting its stringent design constraints and also to the problem of realizing a full 3D isotropic, polarization-independent structure. This work presents the first experimental verification of free-space Veselago-Pendry superlensing using a new class of volumetric metamaterials based on 2D NRI-TL layers that, although polarization-specific, may be easily constructed using available lithographic techniques to interact with free-space sources. An equivalent-circuit model is developed to enable accurate design of the metamaterial's dispersion and transmission characteristics, including those associated with Veselago-Pendry superlensing, and is validated using full-wave simulations. First, a volumetric NRI-TL metamaterial employing fully printed loading elements is fabricated to verify the salient properties of a free-space metamaterial-slab lens. This lens demonstrates diffraction-limited focusing at X-band and, thus, affirms theoretical results that suggest that electrically thick and lossy metamaterials are unable to perform superlensing. Thereafter, a volumetric NRI-TL metamaterial based on discrete lumped elements is designed to meet the conditions of the Veselago-Pendry superlens at 2.40GHz, and experimentally demonstrates a resolution ability over three times better than that afforded by the classical diffraction limit. A microwave superlens designed in this fashion can be particularly useful for illumination and discrimination of closely spaced buried objects over practical distances by way of back-scattering, for example, in tumour or landmine detection, or for targeted irradiation over electrically small regions in tomography or hyperthermia applications. Possible optical implementations of the volumetric topology are also suggested, and finally, a fully isotropic, polarization-independent 3D metamaterial structure related to the volumetric NRI-TL structure is proposed.

Free-space imaging with a resolution beyond that dictated by the classical diffraction limit may be achieved with a `Veselago-Pendry' superlens made from a metamaterial possessing a number of specific properties, including a negative refractive index (NRI). Although a planar NRI transmission-line (NRI-TL) metamaterial based on the periodic lumped loading of a host TL network has successfully verified the phenomenon of superlensing in a 2D microstrip environment, a true Veselago-Pendry superlens capable of interacting with and manipulating fields in free space remained elusive, largely due to the difficulty of meeting its stringent design constraints and also to the problem of realizing a full 3D isotropic, polarization-independent structure. This work presents the first experimental verification of free-space Veselago-Pendry superlensing using a new class of volumetric metamaterials based on 2D NRI-TL layers that, although polarization-specific, may be easily constructed using available lithographic techniques to interact with free-space sources. An equivalent-circuit model is developed to enable accurate design of the metamaterial's dispersion and transmission characteristics, including those associated with Veselago-Pendry superlensing, and is validated using full-wave simulations. First, a volumetric NRI-TL metamaterial employing fully printed loading elements is fabricated to verify the salient properties of a free-space metamaterial-slab lens. This lens demonstrates diffraction-limited focusing at X-band and, thus, affirms theoretical results that suggest that electrically thick and lossy metamaterials are unable to perform superlensing. Thereafter, a volumetric NRI-TL metamaterial based on discrete lumped elements is designed to meet the conditions of the Veselago-Pendry superlens at 2.40GHz, and experimentally demonstrates a resolution ability over three times better than that afforded by the classical diffraction limit. A microwave superlens designed in this fashion can be particularly useful for illumination and discrimination of closely spaced buried objects over practical distances by way of back-scattering, for example, in tumour or landmine detection, or for targeted irradiation over electrically small regions in tomography or hyperthermia applications. Possible optical implementations of the volumetric topology are also suggested, and finally, a fully isotropic, polarization-independent 3D metamaterial structure related to the volumetric NRI-TL structure is proposed.

Developments in nanotechnology and material science have produced optical materials with astonishing properties. Theory and experimentation have demonstrated that, among other properties, the law of refraction is reversed at an interface between a naturally occurring material and these so-called metamaterials. As the technology advances metamaterials have the potential to vastly impact the field of optical science.In this study we provide a foundation for future work in the area of geometric optics and lens design with metamaterials. The concept of negative refraction is extended to derive a comprehensive set of first-order imaging principles as well as an exhaustive aberration theory to 4th order. Results demonstrate congruence with the classical theory; however, negative refraction introduces a host of novel properties. In terms of aberration theory, metamaterials present the lens designer with increased flexibility. A singlet can be bent to produce either positive or negative spherical aberration (regardless of its focal length), its contribution to coma can become independent of its conjugate factor, and its field curvature takes on the opposite sign of its focal power. This is shown to be advantageous in some designs such as a finite conjugate relay lens; however, in a wider field of view landscape lens we demonstrate a metamaterial's aberration properties may be detrimental.This study presents the first comprehensive investigation of metamaterial lenses using industry standard lens design software. A formal design study evaluates the performance of doublet and triplet lenses operating at F/5 with a 100 mm focal length, a 20° half field of view, and specific geometric constraints. Computer aided optimization and performance evaluation provide experimental controls to remove designer-induced bias from the results. Positive-index lenses provide benchmarks for comparison to metamaterial systems subjected to identical design constraints. We find that idiosyncrasies in a metamaterial lens' aberration content can be exploited to produce imaging systems that are superior to their conventional counterparts. However, in some circumstances the reduced low-order aberration content in a metamaterial lens reduces the effectiveness of aberration balancing and stop shifting. Through a series of design experiments the relative advantages and challenges of using metamaterials in lens design are revealed.