[pt] Nos últimos anos, tem aumentado o interesse no uso da transmissão de energia sem fio por acoplamento indutivo em muitas aplicações. Uma das maiores limitações dessa tecnologia é a distância de operação reduzida. Alguns trabalhos recentes sugerem usar materiais artificiais conhecidos como metamateriais para aprimorar a eficiência da transferência de potência ao longo da distância. Devido às suas propriedades eletromagnéticas únicas, tais como permeabilidade magnética negativa, metamateriais podem ser usados para amplificar as ondas evanescentes do campo próximo. No presente trabalho, é estudado o uso de metamateriais eletromagnéticos para aumentar o acoplamento indutivo por meio da amplificação do campo próximo. São apresentados cálculos analíticos e simulações dos metamateriais propostos. O melhoramento da eficiência na transferência de potência é apoiado por evidências experimentais. / [en] Over recent years, the interest in using inductive wireless power transmission for many applications has grown. One of the major limitations of this technology is the reduced operating distance. Some recent works have suggested using artificial materials known as metamaterials to improve the power transfer efficiency over distance. Due to their unique electromagnetic properties, such as negative permeability, metamaterials can be used to enhance the evanescent waves of the near field. In the present work, the usage of an electromagnetic metamaterial to increase the inductive coupling by means of enhanced evanescent waves is studied. Analytical calculations and numerical simulations of the proposed metamaterial are presented. The improvement of the power transfer efficiency is supported by empirical evidences.

Made available in DSpace on 2014-12-17T14:55:05Z (GMT). No. of bitstreams: 1 RobertoRCF_TESE.pdf: 987513 bytes, checksum: 957f5ea8a43b953deeae4b60b26191b2 (MD5) Previous issue date: 2012-05-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work presents a theoretical, numerical and computation analysis of parameters of a rectangular microstrip antenna with metamaterial substrate, fin line as a coupler and also integrated devices like integrated filter antenna. It is applied theory to full-wave of Transverse Transmission Line - TTL method, to characterize the magnitude of the substrate and obtain the general equations of the electromagnetic fields. About the metamaterial, they are characterized by permittivity and permeability tensor, reaching to the general equations for the electromagnetic fields of the antenna. It is presented a study about main representation of PBG(Photonic Band Gap) material and its applied for a specific configuration. A few parameters are simulated some structures in order to reduce the physical dimensions and increase the bandwidth. The results are presented through graphs. The theoretical and computational analysis of this work have shown accurate and relatively concise. Conclusions are drawn and suggestions for future work / Este trabalho apresenta a an?lise te?rica, num?rica e computacional dos par?metros de uma antena de microfita do tipo retangular sobre substrato metamaterial, linha de laminas na forma de acoplador e tamb?m de estruturas integrada como a antena filtro integrada. ? aplicada a teoria de onda completa do m?todo da Linha de Transmiss?o Transversa - LTT, para a caracteriza??o das grandezas do substrato e obten??o das equa??es gerais dos campos eletromagn?ticos. Sobre o metamaterial, os mesmos s?o caracterizados atrav?s de tensores permissividade e permeabilidade, chegando-se ?s equa??es gerais para os campos eletromagn?ticos da antena. ? apresentado um estudo das principais representa??es do material PBG (Photonic Band Gap) e suas aplica??es para determinadas configura??es. S?o simulados v?rios par?metros de algumas estruturas com o intuito de diminuir as dimens?es f?sicas e aumentar a largura de banda das mesmas. Os resultados s?o apresentados atrav?s de gr?ficos. A an?lise te?rico-computacional desse trabalho se mostra precisa e relativamente concisa. S?o apresentadas as conclus?es e sugest?es para trabalhos futuros

The present research is concerned with developing analysis methods for analyzing and exploring finite-amplitude elastic wave propagation through periodic media. Periodic arrangements of materials with high acoustic impedance contrasts can be employed to control wave propagation. These systems are often termed phononic crystals or metamaterials, depending on the specific design and purpose. Design of these systems usually relies on computation and analysis of dispersion band structures which contain information about wave propagation speed and direction. The location and influence of complete (and partial) band gaps is a particularly interesting characteristic. Wave propagation is prohibited for frequencies that correspond to band gaps; thus, periodic systems behave as filters, wave guides, and lenses at certain frequencies. Controlling these behaviors has typically been limited to the manufacturing stage or the application of external stimuli to distort material configurations. The inclusion of nonlinear elements in periodic unit cells offers an option for passive tuning of the dispersion band structure through amplitude-dependence. Hence, dispersion analysis methods which may be utilized in the design of nonlinear phononic crystals and metamaterials are required. The approach taken herein utilizes Bloch wave-based perturbation analysis methods for obtaining closed-form expressions for dispersion amplitude-dependence. The influence of material and geometric nonlinearities on the dispersion relationship is investigated. It is shown that dispersion shifts result from both self-action (monochromatic excitation) and wave-interaction (multi-frequency excitation), the latter enabling dynamic anisotropy in periodic media. A particularly novel aspect of this work is the ease with which band structures of discretized systems may be analyzed. This connection enables topology optimization of unit cells with nonlinear elements. Several important periodic systems are considered including monoatomic lattices, multilayer materials, and plane stress matrix-inclusion configurations. The analysis methods are further developed into a procedure which can be implemented numerically with existing finite-element analysis software for analyzing geometrically-complex materials.

The work presented in this thesis is concerned with the propagation of acoustic waves through phononic crystal systems and their ability to attenuate sound in the low frequency regime. The plane wave expansion method and finite element method are utilised to investigate the properties of conventional phononic crystal systems. The acoustic band structure and transmission measurements of such systems are computed and verified experimentally. Good agreement between band gap locations for the investigative methods detailed is found. The well known link between the frequency range a phononic crystal can attenuate sound over and its lattice parameter is confirmed. This leads to a reduction in its usefulness as a viable noise barrier technology, due to the necessary increase in overall crystal size. To overcome this restriction the concept of an acoustically resonant phononic crystal system is proposed, which utilises acoustic resonances, similar to Helmholtz resonance, to form additional band gaps that are decoupled from the lattice periodicity of the phononic crystal system. An acoustically resonant phononic crystal system is constructed and experimental transmission measurements carried out to verify the existence of separate attenuation mechanisms. Experimental attenuation levels achieved by Bragg formation and resonance reach 25dB. The two separate attenuation mechanisms present in the acoustically resonant phononic crystal, increase the efficiency of its performance in the low frequency regime, whilst maintaining a reduced crystal size for viable noise barrier technology. Methods to optimise acoustically resonant phononic crystal systems and to increase their performance in the lower frequency regime are discussed, namely by introducing the Matryoshka acoustically resonant phononic crystal system, where each scattering unit is composed of multiple concentric C-shape inclusions.

In a communication system, the group delay variation (GDV) causes the distortion of signal and the degradation of symbol error rate. Usually, the compensation of group delay (GD) utilizing positive group delay (PGD) results in further propagation delay. Therefore, this research studies the negative group delay (NGD) behavior of metamaterial. Through analyzing the effects on GD caused by poles and zeros of circuit, the group delay circuit capable of switching between NGD and PGD is presented. Further, adjustable negative group delay circuits (NGDCs) are designed based on the concept of poles and zero. The NGD generated by NGDC is used to achieve the equalization of GD and recover the distorted signal in time domain. Additionally, owing to the limited frequency band of communication, a filter with high selectivity is required to utilize the available bandwidth. The character of left-handed metamaterial is applied to the design of filter for reducing the size and cost of traditional microstrip line filters with high selectivity. Under the balanced condition, composite right/left-handed (CRLH) transmission line behaves right- and left- handed characteristics in different frequency bands. Thus, a coplanar waveguide (CPW) filter with high selectivity, size reduction and low cost is presented utilizing such a CRLH structure.

Left handed metamaterials are one of the most populer topic attracting attentions of scientists nowadays. Metamaterials are engineered materials which can possess inordinary properties when compared with common materials existing in nature. The main structure investigated in this thesis is fishnet metamaterial which is a left handed metamaterial. Firstly some left handed metamaterials and their properties are surveyed. A retrieval procedure in order to obtain permittivity, permeability and refractive index of any periodic material was summarized. Left handedness of fishnet structure was investigated and proven numerically. Effects of change in polarization of an incoming wave to symmetric and asymmetric fishnet structure were searched. A parametric analysis of fishnet structure was done. Phase advance in a three layered fishnet structure was investigated and compared with phase advance in an ordinary material. Fishnet wedge structure was surveyed and negative refraction and negative phase advance in this structure are shown. Finally, some types of disorderness of fishnet structure, then its effects on transmission results and retrieval results are demonstrated. In order to obtain transmission and reflection through a material, CST Microwave Studio&reg / was used. A code following a numerical procedure in order to retrieve constitutive parameters of a periodic structure which was written in Matlab&reg / was used in this thesis.

Efficient electromagnetic solvers based on surface integral equations (SIEs) are developed for the analysis of scattering from large-scale and complex composite structures that consist of piecewise homogeneous magnetodielectric and perfect electrically/magnetically conducting (PEC/PMC) regions. First, a multiple-grid extension of the adaptive integral method (AIM) is presented for multi-region problems. The proposed method accelerates the iterative method-of-moments solution of the pertinent SIEs by employing multiple auxiliary Cartesian grids: If the structure of interest is composed of K homogeneous regions, it introduces K different auxiliary grids. It uses the k^{th} auxiliary grid first to determine near-zones for the basis functions and then to execute AIM projection/anterpolation, propagation, interpolation, and near-zone pre-correction stages in the k^{th} region. Thus, the AIM stages are executed a total of K times using different grids and different groups of basis functions. The proposed multiple-grid AIM scheme requires a total of O(N^{nz,near}+sum({N_k}^Clog{N_k}^C)) operations per iteration, where N^{nz,near} denotes the total number of near-zone interactions in all regions and {N_k}^C denotes the number of nodes of the k^{th} Cartesian grid. Numerical results validate the method’s accuracy and reduced complexity for large-scale canonical structures with large numbers of regions (up to 10^6 degrees of freedom and 10^3 regions). Then, a Green function modification approach and a scheme of Hankel- to Teoplitz-matrix conversions are efficiently incorporated to the multiple-grid AIM method to account for a PEC/PMC plane. Theoretical analysis and numerical examples show that, compared to a brute-force imaging scheme, the Green function modification approach reduces the simulation time and memory requirement by a factor of (almost) two or larger if the structure of interest is terminated on or resides above the plane, respectively. In addition, the SIEs are extended to cover structures composed of metamaterial regions, PEC regions, and PEC-material junctions. Moreover, recently introduced well-conditioned SIEs are adopted to achieve faster iterative solver convergence. Comprehensive numerical tests are performed to evaluate the accuracy, computational complexity, and convergence of the novel formulation which is shown to significantly reduce the number of iterations and the overall computational work. Lastly, the efficiency and capabilities of the proposed solvers are demonstrated by solving complex scattering problems, specifically those pertinent to analysis of wave propagation in natural forested environments, the design of metamaterials, and the application of metamaterials to radar cross section reduction. / text

The goal of the research reported in this thesis is to establish the feasibility of a novel optical architecture for an optical route & select circuit switch suitable for implementation as a photonic integrated circuit. The proposed architecture combines Optical Phased Array (OPA) switch elements implemented as multimode interference coupler based Generalised Mach-Zehnder Interferometers (GMZI) with a planar Lüneburg lens-based optical transpose interconnection network implemented using graded metamaterial waveguide slabs. The proposed switch is transparent to signal format and, in principle, can have zero excess insertion loss and scale to large port counts. These switches will enable the low-energy consumption high capacity communications network infrastructure needed to provide environmentally-friendly broadband access to all. The thesis first explains the importance of switch structures in optical communications networks and the difficulties of scaling to a large number of switch ports. The thesis then introduces the Talbot effect, i.e. the self-imaging of periodic field distributions in free space. It elaborates on a new approach to finding the phase relations between pairs of Talbot image planes at carefully selected positions. The free space Talbot effect is mapped to the waveguide Talbot effect which is fundamental to the operation of multimode interference couplers (MMI). Knowledge of the phase relation between the MMI ports is necessary to achieve correct operation of the GMZI OPA switch elements. An outline of the design procedures is given that can be applied to optimise the performance of MMI couplers and, as a consequence, the GMZI OPA switch elements. The Lüneburg Optical Transpose Interconnection System (LOTIS) is introduced as a potential solution to the problem of excessive insertion loss and cross-talk caused by the large number of crossovers in a switch fabric. Finally, the thesis explains how a Lüneburg lens may be implemented in a graded ‘metamaterial’, i.e. a composite material consisting of ‘atoms’ arranged on a regular lattice suspended in a host by nano-structuring of silicon waveguide slabs using a single etch-step. Furthermore, the propagation of light in graded almost-periodic structures is discussed. Detailed consideration is given to the calibration of the local homogenised effective index; in terms of the local parameters of the metamaterial microstructure in the plane and the corrections necessary to accommodate slab waveguide confinement in the normal to the plane. The concept and designs were verified by FDTD simulation. A 4×4 LOTIS structure showed correct routing of light with a low insertion loss of -0.25 dB and crosstalk of -24.12 dB. An -0.45 dB excess loss for 2D analysis and an -0.83 dB insertion excess loss for 3D analysis of two side by side metamaterial Lüneburg lenses with diameter of 15 μm was measured, which suggests that the metamaterial implementation produces minimal additional impairments to the switch.

La théorie d'homogénéisation élastodynamique des matériaux hétérogènes initiée par J.R. Willis il y a environ une trentaine d'années a récemment reçu une très grande attention. D'après cette théorie qui est mathématiquement exacte, la loi constitutive homogénéisée est non locale en espace et en temps ; le tenseur des contraintes dépend non seulement du tenseur des déformations mais aussi de la vitesse ; la quantité du mouvement dépend à la fois de la vitesse et du tenseur des déformations, faisant apparaître en général une masse anisotrope. Ces propriétés constitutives effectives, qui pourraient être surprenantes d'un point de vue mécanique classique, se révèlent en fait très utiles pour la conception de métamatériaux acoustiques et de capes acoustiques. Ce travail de thèse consiste essentiellement à proposer et développer deux méthodes numériques efficaces pour déterminer les propriétés élastodynamiques effectives des matériaux périodiquement hétérogènes. La première méthode relève de la méthode des éléments finis alors que la deuxième méthode est basée sur la transformée de Fourier rapide. Ces deux méthodes sont d'abord élaborées pour une microstructure périodique 3D quelconque et ensuite implantées pour une microstructure périodique 2D quelconque. Les avantages et les inconvénients de chacune de ces deux méthodes sont comparés et discutés. A l'aide des méthodes numériques élaborées, la théorie de Willis est appliquée au calcul élastodynamique sur un milieu infini hétérogène et celui homogénéisé. Les différents cas d'homogénéisabilité et de non-homogénéisabilité sont discutés / The elastodynamic homogenization theory of heterogeneous materials initiated by J.R. Willis about thirty years ago has recently received considerable attention. According to this theory which is mathematically exact, the homogenized constitutive law is non-local in space and time; the stress tensor depends not only on the strain tensor but also on the velocity; the linear momentum depends on both the velocity and the strain tensor, making appear an anisotropic mass tensor in general. These effective constitutive properties, which may be surprising from a classical mechanical point of view, turn out in fact to be very useful for the design of acoustic metamaterials and acoustic cloaks. The present work is essentially to propose and develop two efficient numerical methods for determining the effective elastodynamic properties of periodically heterogeneous materials. The first method belongs to the finite element method while the second method is based on the fast Fourier transform. These two methods are first developed for any 3D periodic microstructure and then implanted for any 2D periodic microstructure. The advantages and disadvantages of each of these two methods are compared and discussed. Using the elaborated numerical methods, the Willis theory is applied to the elastodynamic computation over the infinite heterogeneous medium and the homogenized one. The various cases of homogeneisability and non-homogeneisability are discussed

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-02-03T20:53:53Z No. of bitstreams: 1 CarlosGomesDeMoura_TESE.pdf: 3433737 bytes, checksum: 78095bf1c8dfe0fa9a5ac309049980a1 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-02-04T00:22:45Z (GMT) No. of bitstreams: 1 CarlosGomesDeMoura_TESE.pdf: 3433737 bytes, checksum: 78095bf1c8dfe0fa9a5ac309049980a1 (MD5) / Made available in DSpace on 2016-02-04T00:22:45Z (GMT). No. of bitstreams: 1 CarlosGomesDeMoura_TESE.pdf: 3433737 bytes, checksum: 78095bf1c8dfe0fa9a5ac309049980a1 (MD5) Previous issue date: 2015-02-06 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Os metamateriais tem atra?do uma grande aten??o nas ultimas d?cadas, em decorr?ncia de suas propriedades eletromagn?ticas n?o serem encontradas na natureza. Desde que os metamateriais passaram a ser sintetizados atrav?s da inser??o de inclus?es artificialmente fabricadas num meio homog?neo especificado, facilitou ao pesquisador uma larga cole??o de par?metros independentes, como, por exemplo, as propriedades eletromagn?ticas do material. Foram realizadas investiga??es das propriedades dos ressoadores em anel e dos metamateriais. Foi apresentado um estudo das principais teorias que explicam com clareza a supercondutividade. As teorias BCS, Equa??es de London e modelo dos Dois Fluidos s?o as teorias que d?o suporte a aplica??o dos supercondutores nas antenas de microfita. Assim, esta Tese de Doutorado apresenta uma an?lise te?rica, num?rico-computacional e experimental, utilizando o formalismo de onda completa, atrav?s da aplica??o do m?todo da Linha de Transmiss?o Transversa ? LTT, aplicado no Dom?nio da Transformada de Fourier (FTD). O LTT ? um m?todo de onda completa, que tem como regra a obten??o dos campos eletromagn?ticos em termos dos componentes transversais ? estrutura. A inclus?o do patch supercondutor ? feita utilizando-se a condi??o de contorno complexa resistiva. S?o obtidos resultados da freq??ncia de resson?ncia em fun??o dos par?metros da antena. Para valida??o das an?lises foram elaborados programas computacionais na linguagem Fortran, simula??es no software comercial, sendo as curvas tra?adas no software comercial e no software Matlab, al?m de se comparar o patch convencional com o supercondutor e depois se comparar um substrato metamaterial com um convencional, juntando o substrato com o patch, verificando o que melhora em ambos os quesitos, demonstrando a utiliza??o pr?tica destas estruturas em antenas fabricadas em laborat?rio. / Metamaterials have attracted great attention in recent decades, due to their electromagnetic properties which are not found in nature. Since metamaterials are now synthesized by the insertion of artificially manufactured inclusions in a specified homogeneous medium, it became possible for the researcher to work with a wide collection of independent parameters, for example, the electromagnetic properties of the material. An investigation of the properties of ring resonators was performed as well as those of metamaterials. A study of the major theories that clearly explain superconductivity was presented. The BCS theory, London Equations and the Two-Fluid Model are theories that support the application of superconducting microstrip antennas. Therefore, this thesis presents theoretical, numerical and experimental-computational analysis using full-wave formalism, through the application of the Transverse Transmission Line ? LTT method applied in the Fourier Transform Domain (FTD). The LTT is a full wave method, which, as a rule, obtains the electromagnetic fields in terms of the transverse components of the structure. The inclusion of the superconducting patch is performed using the complex resistive boundary condition. Results of resonant frequency as a function of antenna parameters are obtained. To validate the analysis, computer programs were developed using Fortran, simulations were created using the commercial software, with curves being drawn using commercial software and MATLAB, in addition to comparing the conventional patch with the superconductor as well as comparing a metamaterial substrate with a conventional one, joining the substrate with the patch, observing what improves on both cas