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Ni, Sisi (Sisi Sophie). "Phononic metamaterials based on complex geometries : "a new kind of metamaterial"." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89957.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>Facing the growing challenges of energy, environment, security and disease treatment, the demand for novel materials are growing. While the material centric approach have resulted in development of new materials for advanced applications, we introduce a geometric approach as a complementary point of view for further innovation in this ever expanding and growing field. Inspired by the ubiquitous fractals-like geometry of in natures, the scale transformation (i.e. dilation or contraction) is included in the framework since fractal geometries shows structures at all scales (usually discrete and finite in physical world). We developed our framework using metamaterials since it enable us to design "atoms" or "molecules" and their relative arrangement with greater freedom (i.e. not limited by the chemical bond or ionic bond in classical materials system). We studied metamaterials using prefractals from both exact-self similar fractal and random fractal samples. For exact-self similar fractals, we choose H tree based prefractals and Hilbert Curve prefractals bounded system given their unique geometric properties and wide applications. Guided by the framework, we investigated several key parameters (e.g. level of iteration, geometric anisotropy, impedance contrast, arrangement of subunit, resolution) that would dictate the dispersion behavior of the system. It was found that for exact-self similar prefractals, multiple spectrum bandgaps (i.e. broadband response) can be achieved with increased level of iterations where translation symmetry is imposed through boundary condition. Furthermore, the transition from scale dependence and independent described by the general framework has been observed for all the samples we studied. Furthermore, for single prefractal resonator, subwavelength (~1/75[lambda]) behavior has been observed and explained using a simple analytical model. For metamaterials based on fractional Brownian motion, the Hurst constant is found to be a good indicator of phononic behavior of the system, besides other parameters studied. Our findings does not only expand the repertoire for novel materials by introducing the ubiquitous yet unconventional geometry to metamaterials; but also have interdisciplinary applications in biology, seismology, arts, hence shine lights on our understanding of nature.<br>by Sisi (Sophie) Ni.<br>Ph. D.
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Strikwerda, Andrew. "Metamaterial enhanced coupling." Thesis, Boston University, 2012. https://hdl.handle.net/2144/31611.
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Thesis (Ph.D.)--Boston University<br>PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.<br>In the past decade interest in metamaterials has risen dramatically. This is due, in large part, to metamaterials' ability to exhibit electromagnetic behavior not normally found in nature. This is because these artificial structures display a strong electromagnetic response as a result of their geometry, as opposed to their chemistry, and that response typically dominates that of the substrate they are placed on. As a result, metamaterials can couple free space radiation in previously unheard of ways, and in this thesis I examine several of these coupling mechanisms.
After an appropriate discussion of theoretical and experimental tools required for metamaterial study, the thesis turns to the metamaterial substrate and explores the coupling effects of the metamaterial and the substrate itself. We discuss the theory and experimentally demonstrate that the metamaterial and substrate composite can couple free space radiation for use in enhanced dielectric sensing, perfect absorption, and even mechanical deflection for electromagnetic detection.
In addition to coupling with dielectric materials, the near field response of a metamaterial can also couple with another metamaterial. Subsequently, this thesis investigates the coupling between a pair of identical split ring resonators, and develops a general framework for evaluating the mode hybridization that results from their near field interaction. In fact, we find that the near field coupling is extremely sensitive to the relative orientation of the two metamaterials, and results in mode splitting between the two resonators. By manipulating their lateral displacement, the coupling, and the mode splitting, can be altered. In this way, an unprecedented modulation of the metamaterial response is demonstrated.
Finally, we turn our attention to the effects that metamaterial behavior has on the far field response. Specifically, we focus on the symmetry, or lack thereof, of the unit cell and show that it manifests itself as a birefringence in the far field. As a result, metamaterials can be used as wave retarders to couple between polarization states. Herein we analyze this behavior and experimentally demonstrate functioning metamaterial based terahertz waveplates that are highly efficient at a previously unachieved sub wavelength size.<br>2031-01-01
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Li, Lianbo. "Metamaterial based superdirectivity." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:65f10679-cbf2-4c86-897e-8121225c44eb.
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A model-supporting, simple, compact, robust and high efficiency two- element parasitic superdirective array comprising electrically small reso- nant metamaterial elements, namely singly split resonator rings (SSRRs), is predicted by an analytical model and is verified by CST simulation re- sults. The analytical model is built by combining a method of calculating a two-SSRR array's far fild radiated energy density and a well working equivalent circuit for a two-SSRR parasitic array. This model is capable of easily but accurately predicting the far field radiation behaviours of an electrically small parasitic array of two SSRRs (the two SSRRs are not necessarily standard and identical), based on certain information of the array, namely the SSRRs' dimensions, the SSRRs' electrical components (L, C and R), the SSRRs' rotating orientation angles (α<sub>1</sub> and α<sub>2</sub>), the two SSRRs's separation (d) and the array's operation frequency. The impor- tance of this analytical model in designing parasitic superdirective arrays is discussed. Simulation results show that the model predicted two-SSRR parasitic superdirective structure (the `CC' structure) can achieve an end- fire directivity of 4.36, with an elements' separation d = 4mm working at 1:914GHz, and can maintain an efficiencyciency as high as 98:6%. After a short discussion of the design principle behind the `CC' structure, improved su- perdirective structures of are identified and studied based on simulation results. Among these structures, the 'CCLr' structure can achieve the largest directivity value of 5.06 (very close to 5.25, the theoretical limit value of a two-dipole array) with a moderate efficiency of 81:4%. A com- parison between these two-SSRR parasitic superdirective structures (the `CC' and its improved versions) and two commercial two-element Yagi an- tennas show that these two-SSRR structures achieve better directive per- formances than the commercial two-element Yagi antennas do. Through performing the study of near field energy ow for magnetic dipole based structures (analytical results) and SSRR based structures (simulation re- sults), with the help of the concept of causal surfaces, the physical reason behind the superdirectivity phenomenon is revealed.
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Shepard, III Ralph Hamilton. "Metamaterial Lens Design." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/194734.
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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.
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Prat, Camps Jordi. "Shaping magnetic felds with superconductor-metamaterial hybrids." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/309138.
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El magnetisme és molt important en diverses àrees de la ciència i la tecnologia, cobrint un rang molt ampli d'escales i temes. En aquesta tesis presentem el desenvolupament teòric i la realització experimental de diversos dispositius nous pel control dels camps magnètics. Pel disseny d'aquests s'han emprat diverses estratègies; la teoria de l'òptica de transformació s'ha combinat amb resultats obtinguts directament de les equacions de Maxwell, i les propostes idealitzades han esdevingut dispositius reals mitjançant la combinació de materials ferromagnètics i superconductors formant diferents metamaterials magnètics.
En primer lloc presentem l'estudi referent a les capes invisibilitat magnètica. De manera anàloga a com actuaria una capa d'invisibilitat per llum visible, una capa d'invisibilitat magnètica evita que els camps penetrin al seu interior al mateix temps que la capa i el seu contingut són magnèticament indetectables des de l'exterior. En aquesta tesis presentem el desenvolupament de diferents dissenys de capa d'invisibilitat, centrant-nos en un sistema bicapa superconductor-ferromagnètic. Aquesta bicapa ha estat construïda i provada amb èxit.
La concentració de camps magnètics també ha estat estudiada. Hem dissenyat una capa concentradora magnètica cilíndrica, la qual concentra els camps magnètics aplicats externs en el seu orifici interior. Alhora, aquesta mateixa capa expulsa el camp magnètic cap a l'exterior quan la font de camp se situa a l'orifici interior. S'han fabricat algunes d'aquestes capes concentradores emprant materials superconductors i ferromagnètics i les seves propietats s'han verificat experimentalment. A més a més també hem demostrat que les capes permeten incrementar l'acoblament magnètic entre circuits. Aquesta propietat l'hem aplicat experimentalment per demostrar que les capes concentradores permeten millorar la transmissió d'energia elèctrica sense fils.
Seguidament hem estudiat la transmissió de camps magnètics. A diferència de les ones electromagnètiques que es propaguen fàcilment dins de guies d'ones o fibres òptiques, els camps magnètics decauen ràpidament a mesura que ens allunyem de la font. A fi de superar aquesta limitació hem desenvolupat un sistema de "mànega magnètica" que permet la transferència de camps magnètics estàtics fins a llargues distàncies i que es pot construir combinant adequadament capes superconductores i ferromagnètiques. El disseny l'hem validat a partir de simulacions numèriques i desenvolupaments analítics. Algunes "mànegues" s'han fabricat i les seves propietats ha estat experimentalment demostrades.
Finalment hem desenvolupat un forat de cuc magnètic. Inspirats pels forats de cuc cosmològics, que connecten dos punts de l'espai a través d'un camí que se situa fora de l'espai tridimensional convencional, hem desenvolupat un dispositiu capaç de crear l'efecte equivalent per camps magnètics estàtics. Així, el forat de cuc magnètic connecta magnèticament dos punts de l'espai a través d'un camí que és magnèticament indetectable. El dispositiu està format per una "mànega magnètica" recoberta d'una esfera superconductora i una "metasuperfície" ferromagnètica. Les seves propietats han estat estudiades teòricament i el dispositiu ha estat construït. Això ha permès demostrar, també, les seves característiques de manera experimental.
En resum, aquesta tesis conté el desenvolupament teòric i la realització experimental de diversos dispositius que permeten la manipulació de camps magnètics. A banda d'estudiar diversos problemes concrets com la invisibilitat magnètica, la concentració o la transmissió de camps, la present recerca ha donat lloc a tot un conjunt d'"eines" que permeten el control i la manipulació de camps magnètics d'una manera general.<br>Magnetism is very important in various areas of science and technology, covering a wide range of scales and topics. In this thesis we present the theoretical development and the experimental realization of various novel devices to control magnetic fields. Their design is based on different strategies; transformation optics theory is combined with solutions directly obtained from Maxwell equations, and ideal designs are turned into real devices combining superconducting and ferromagnetic materials forming different magnetic metamaterials.
We first study the cloaking of magnetic fields. Analogous to the concept of an "invisibility"
cloak for light, a cloak for static magnetic fields prevents fields to penetrate in its interior and makes the cloak itself and its content magnetically undetectable from the exterior. Different designs of magnetic cloak are developed and a bilayer superconductor-ferromagnetic cylindrical cloak is experimentally built and tested.
The concentration of magnetic fields is also addressed. A cylindrical magnetic concentrating shell is designed, demonstrating that it concentrates external fields in its interior hole and it also expels the field of internal sources towards the exterior. Different concentrating shells are experimentally built using superconducting and ferromagnetic materials and their properties are validated. We also demonstrate that concentrating shells increase the magnetic coupling between circuits. We apply this property to experimentally demonstrate they enhance the wireless transfer of power.
The transfer of static magnetic fields is also studied. Different from electromagnetic waves that easily propagate in waveguides or optical fibers, magnetic fields rapidly decay as one moves far from the source. To overcome this limitation we develop the magnetic hose, a design that allows to transfer static magnetic fields to arbitrary distances and can be realized with an adequate combination of superconducting and ferromagnetic shells. The design is validated using numerical calculations and analytical developments. Some hoses are experimentally built and their properties are demonstrated.
Finally we develop a magnetic wormhole. Inspired by cosmological wormholes, that connect two points in space through a path that is out of the conventional 3D space, we study an analogous effect for static magnetic fields. The magnetic wormhole magnetically connects two points in space through a path that is magnetically undetectable. It is composed of an interior magnetic hose surrounded by a spherical superconducting shell and a spherical ferromagnetic
metasurface. An actual magnetic wormhole is experimentally built and its properties are demonstrated.
To sum up, this thesis contains the theoretical development and the experimental realization of different devices to manipulate magnetic fields. In addition to addressing different particular problems, like magnetic cloaking, concentration or magnetic field transfer, this research has resulted in a whole set of new "tools" to shape and control static magnetic fields in a general way.
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Tan, Szu Hau. "Metamaterial for Radar Frequencies." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/17465.
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Approved for public release; distribution is unlimited<br>The objective of this thesis is to investigate a new design of periodic metamaterial (MTM) structure for radar cross-section (RCS) reduction application on aircraft and ships. MTMs are man-made materials, not found in nature, that exhibit unusual properties in the radio-, electromagnetic-, and optical-wave bands. The cells of these periodic MTM structures must be much smaller than the wavelength of the frequency of interest. In a MTM, the structure and dimensions of the design at the frequency of interest can produce negative values of permeability and/or permittivity, which define the electrical properties of the MTM. This study looks at various designs of absorbing layers presented in technical papers and verifies the results in simulations. Modifications are done to the existing designs to achieve good absorption level at the radar-frequency band of interest. Modeling and simulation are done in Microwave Studio by Computer Simulation Technology (CST). The S-parameters S11 (reflection coefficient) and S12 (transmission coefficient) are used to investigate the performance of the MTM as a radar-frequency absorber.
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Demetriadou, Angela. "Studies of metamaterial structures." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/11396.
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McMahan, Michael T. "Metamaterial absorbers for microwave detection." Thesis, Monterey, California: Naval Postgraduate School, 2015. http://hdl.handle.net/10945/45904.
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Approved for public release; distribution is unlimited<br>The development of high-power microwave weapons and dependence on electronics in modern weapon systems presents a high-power microwave weapons threat in future military conflicts. This study experimentally determines the absorption characteristics of simple metamaterial devices to potentially be used as protection and identification mechanisms, constructed through standard printed circuit board manufacturing processes, in the microwave region. Experimental results and analysis techniques are presented confirming absorption peaks in the anticipated microwave frequency range. The experimental results are compared to a finite-element model of these metamaterials confirming the ability to accurately model and predict absorption characteristics of similar metamaterial structures. Utilization of the absorption characteristics of these types of metamaterial structures to develop a microwave detector and/or equipment shielding is discussed. Several applications for such type of a detector are presented.
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Wang, Weijen 1980. "Directive antenna using metamaterial substrates." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17995.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.<br>Includes bibliographical references (p. 83-86).<br>Using a commercially available software(CST Microwave Studio®), two kinds of simulations have been carried out on different metamaterials in the microwave regime. One is transmission and reflection of a unit cell in a waveguide, and the other is parallel plate slab farfield radiation. The S-parameters are obtained from the wave-guide simulation and are used to retrieve the effective permittivity and permeability with which we can estimate the farfield radiation using analytic method. Thus, by comparing the farfield radiation from two different methods, analytic and slab simulation, we find that the analytic method is able to indicate many major features of the slab simulation's farfield results, implying that within a certain frequency range, we can treat the metamaterial as being homogeneous. After comparing the radiation performance of different metamaterial as antenna substrates, a structure is chosen to be optimized in such a way that it improves in radiation power, beamwidth, and bandwidth.<br>by Weijen Wang.<br>M.Eng.
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Hasan, Md Kamrul. "Metamaterial Antenna for Medical Applications." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367944880.
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Erentok, Aycan. "Metamaterial-Based Electrically Small Antennas." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/195725.
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The introduction of the so-called metamaterials, artificial materials which have engineered electromagnetic responses that are not readily available in nature, and their exotic properties have provided an alternate design approach that has led to improved performance characteristics of several radiating and scattering systems. This dissertation work introduces an antenna design paradigm based on the incorporation of metamaterials, which have negative permittivity and/or permeability medium properties, with simple radiating elements to obtain efficient electrically-small antenna systems. The most general analytical form of the electrically-small electric dipole antenna in the presence of a multilayered metamaterial shell system is developed and the total radiated power of this system is optimized using a hybrid genetic algorithm(GA)-MATLAB optimization approach. The numerical modeling of more realistic antenna-metamaterial systems confirms the analytical results. The theoretical and numerical studies of their radiation and resonance behaviors have led this dissertation work to the discovery of the first physical two- (2D) and three-dimensional (3D) metamaterial based and inspired efficient electrically-small antenna systems. Several novel metamaterial-inspired electrically-small antenna systems, i.e., the 2D and 3D electrical- and magnetic-based EZ antennas, are reported and are shown to be naturally matched to a 50 Ohms source and, hence, to have high overall efficiencies. The proposed 2D and 3D EZ antenna systems are linearly scalable to a wide range of frequencies. Several versions of the 2D EZ antennas were fabricated and tested. The measurement results confirm the performance predictions. This dissertation also considers several new metamaterial structures. An artificial magnetic conductor (AMC) slab is designed to achieve its in-phase reflection properties in the X-band at 10 GHz without the presence of a PEC ground plane. A block of this AMC structure was designed, fabricated, tested, and then integrated with a dipole antenna to realize a resonant low profile antenna system having a large front-to-back ratio.
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Ferrer, González Pere Josep. "Multifunctional metamaterial designs for antenna applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/312841.
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Over the last decades, Metamaterials (MTMs) have caught the attention of the scientific community. Metamaterials are basically artificially engineered materials which can provide unusual electromagnetic properties not present in nature. Among other novel and special EM applications, such as the negative refraction index (NRI) application, Metamaterials allow the realisation of perfect magnetic conductors (PMCs), which are of interest in the development of smaller and more compact antenna systems composed of one or more antennas.
In this context, this thesis is focused on investigating the feasibility of using metamaterial structures to improve the performance of antennas operating at the microwave frequencies. The metamaterial design process is challenging because metamaterials are primarily composed of resonant particles, and hence, their response is frequency dependent due to the dispersive behaviour of their effective medium properties. However, one can take advantage of this situation by exploiting those strange properties while finding other antenna applications for such metamaterial designs. For the case of the PMC applications, the relative magnetic permeability values are negative, because they are found just above the resonance of the metamaterial.
This thesis investigates several antenna applications of artificial magnetic materials (AMMs). The initial work is devoted to the design of a spiral resonator (SR) AMM slab to realise a low profile reflector dipole antenna by taking advantage of its PMC response. The spiral resonator has been used due to its reduced unit cell size when compared to other metamaterial resonators, leading to a more homogeneous metamaterial structure. In addition, a bidirectional PMC spacer has been applied to produce a small and compact antenna system composed of two monopole antennas, although the concept may be applied to other antenna types. A third application as an AMC reflector are the transpolarising surfaces, where the incident electric field plane wave is reflected at a polarisation rotation angle of 90 degrees. Such surfaces may be of interest to produce high cross-polar response reflecting devices, like the modified trihedral corner reflector that has been tested for polarimetric synthetic aperture radar (PolSAR) purposes.
Another application of the SR AMM metamaterial is the patch antenna with a magneto-dielectric loading. The relative magnetic permeability of the AMM metamaterial has values over the unity in the frequency band below the resonance. As a consequence, the patch antenna can be miniaturised without reducing its bandwidth of operation, in contrast to a typical high dielectric permittivity substrate.
Finally, the SR AMM metamaterial also presents values of relative magnetic permeability between zero and the unity (MNZ). In such a case, the SR AMM metamaterial has been applied as an MNZ cover of a slot antenna, devoted to increasing the broadside radiated power and directivity of the antenna.<br>En las últimas décadas, los Metamateriales (MTMs) han captado la atención de la comunidad científica internacional. Los metamateriales son básicamente materiales artificiales diseñados que tienen propiedades electromagnéticas inusuales no presentes en la naturaleza. Aparte de otras aplicaciones innovadoras en electromagnetismo, como la posibilidad de un material con un índice de refracción negativo (NRI), los metamateriales permiten realizar los conductores magnéticos perfectos (PMCs), que podrían ser de gran utilidad para implementar sistemas de múltiples antenas más pequeños y compactos. En este contexto, esta tesis se centra en investigar el uso de diferentes diseños de metamateriales para mejorar las prestaciones de sistemas radiantes o antenas que trabajan a frecuencias de microondas. El proceso de diseño de los metamateriales es complicado, porque los metamateriales están compuestos de resonadores magnéticos, y consecuentemente, su respuesta varía con la frecuencia a causa de la naturaleza dispersiva de sus parámetros de medio efectivo. No obstante, se pueden aprovechar estas propiedades extrañas para encontrar otras aplicaciones interesantes en antenas. Para el caso de aplicaciones como PMC, el valor de la permeabilidad magnética relativa toma principalmente valores negativos, ya que se encuentran después de la resonancia del metamaterial. Esta tesis realiza el estudio de diferentes aplicaciones de antenas con materiales magnéticos artificiales (AMMs). Primeramente, se ha diseñado un metamaterial AMM compuesto de resonadores en espiral (SRs), que se aplica para realizar un reflector de perfil bajo con una antena dipolo, aprovechando la respuesta PMC que proporciona el metamaterial. Se han utilizado resonadores en forma de espiral porque tienen una celda unidad más reducida al compararla con la de otros resonadores metamaterials, produciendo así una estructura metamaterial más homogénea. Además, un diseño PMC bidireccional ha permitido diseñar un sistema pequeño y compacto de dos antenas monopolo, aunque este concepto se puede aplicar a otros tipos de antenas. Una tercera aplicación como reflector AMC es el de pantalla transpolarizadora, dónde una onda eléctrica plana incidente es reflejada con un ángulo de rotación de 90 grados. Estas pantallas pueden servir para realizar dispositivos reflectores con una respuesta cruzada alta, como pasa con un triedro modificado que se ha probado con éxito en aplicaciones como calibrador de radar de apertura sintética polarimétrico (PolSAR). El metamaterial SR AMM también se ha utilizado como substrato magneto-dieléctrico de una antena impresa o patch. La permeabilidad magnética relativa de este metamaterial toma valores más grandes que la unidad en el rango de frecuencias por debajo de la resonancia. Por esto, la antena patch se puede miniaturizar sin reducir sus prestaciones de ancho de banda de operación, caso contrario a cuando se utilizan substratos de permitividad dieléctrica alta. Finalmente, el metamaterial SR AMM también toma valores de permeabilidad magnética relativa entre cero y la unidad (MNZ). En este caso, el metamaterial SR AMM se ha aplicado como un superestrato MNZ de una antena de ranura o slot, con la intención de incrementar la potencia radiada y la directividad de la antena.
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Hedayati, Mehdi Keshavarz [Verfasser]. "Tunable Plasmonic Metamaterial / Mehdi Keshavarz Hedayati." Kiel : Universitätsbibliothek Kiel, 2014. http://d-nb.info/1055941444/34.
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Peruch, Silvia. "Ultrafast properties of plasmonic nanorod metamaterial." Thesis, King's College London (University of London), 2016. https://kclpure.kcl.ac.uk/portal/en/theses/ultrafast-properties-of-plasmonic-nanorod-metamaterial(d981b5e4-b959-4193-8cf1-219b68de08d6).html.
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Plasmonic metamaterials have customized linear and nonlinear optical properties. This thesis investigates the properties of an anisotropic plasmonic metamaterial, consisting of aligned, interacting gold nanorods, to perform ultrafast light modulation, exploiting the intrinsic Kerr nonlinearity of gold. This e ect is based on an illumination-intensity-dependent change in the gold's permittivity, which takes place on ultrafast timescales and induces the intensity-dependent change of the metamaterial's re ection and transmission. A comprehensive theoretical and numerical analysis of the linear and nonlinear response of various con gurations of the metamaterial is performed and compared to experimental results. A new family of hyperbolic waveguided modes above the e ective plasma frequency, enabled by spatial dispersion, is identi ed. The strong nonlinear response and the dynamic modulation capabilities associated with the excitation of the waveguided modes is investigated. The presence of strong electron temperature gradients in the nanorods induced by a control light is shown to determine a stronger nonlinear modulation and to in uence the dynamic response, leading to subpicosecond time recovery components of the nonlinearity. Weak and strong coupling between molecular excitons and the metamaterial's modes can be achieved using core-shell nanorod geometries. The coherent interaction of molecular J-aggregates with coreshell nanorod arrays is analyzed in both the weak and strong coupling regimes. Subpicosecond components of the modulation are determined in the strong coupling conditions. The design of the optical response of the gold nanorod and core-shell metamaterials is studied through the near- to mid- Infrared, key spectral regions for molecular ngerprinting in chemical sensing and absorption spectroscopy. The applicability limits of the analytic approaches using the quasi-static and e ective medium approximations is tested. The results show great potential of the plasmonic nanorod metamaterial for ultrafast nonlinear optics in free-space and integrated applications, in a broad spectral range.
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Phillips, Allan T. "Resonant terahertz absorption using metamaterial structures." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/27888.
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The Sensor Research Lab at the Naval Postgraduate School is developing a real-time THz imaging camera. Vital to its design is the metamaterial absorbing layer (metafilm) within each pixel that allows for THz absorption. While there are numerous applications in the THz region, sensors and sources for THz energy have much room for improvement. The use of metamaterial technology for the purpose of a THz sensor has the potential to reduce costs while greatly improving sensitivity performance. The Sensor Research Lab has fabricated metafilms capable of near 100 percent absorption. In this research project, absorption characteristics of a set of metamaterials were measured using Fourier transform THz spectroscopy and modeled using an RLC circuit. The model provides a good description of the absorption characteristics and should assist in better understanding of the electromagnetic interactions within the metafilm.
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Liu, Xianliang. "Infrared Metamaterial Absorbers: Fundamentals and Applications." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3829.
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Thesis advisor: Willie J. Padilla<br>Realization of an ideal electromagnetic absorber has long been a goal of engineers and is highly desired for frequencies above the microwave regime. On the other hand, the desire to control the blackbody radiation has long been a research topic of interest for scientists--one particular theme being the construction of a selective emitter whose thermal radiation is much narrower than that of a blackbody at the same temperature. In this talk, I will present the computational and experimental work that was used to demonstrate infrared metamaterial absorbers and selective thermal emitters. Based on these work, we further demonstrate an electrically tunable infrared metamaterial absorber in the mid-infrared wavelength range. A voltage potential applied between the metallic portion of metamaterial array and the bottom ground plane layer permits adjustment of the distance between them thus altering the electromagnetic response from the array. Our device experimentally demonstrates absorption tunability of 46.2% at two operational wavelengths. Parts of this thesis are based on unpublished and published articles by me in collaboration with others. The dissertation author is the primary researcher and author in these publications. The text of chapter two, chapter five, and chapter seven is, in part, a reprint of manuscript being prepared for publication. The text of chapter three is, in part, a reprint of material as it appears in Physical review letters 104 (20), 207403. The text of chapter four is, in part, a reprint of material as it appears in Physical Review Letters 107 (4), 45901. The text of chapter six is, in part, a reprint of material as it appears in Applied Physics Letters 96, 011906<br>Thesis (PhD) — Boston College, 2013<br>Submitted to: Boston College. Graduate School of Arts and Sciences<br>Discipline: Physics
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Brito, Davi Bibiano. "Metamaterial inspired improved antennas and circuits." Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15152.
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Previous issue date: 2010-12-06<br>Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior<br>Metamaterials exhibiting negative refraction have attracted a great amount of attention
in recent years mostly due to their exquisite electromagnetic properties. These materials are
artificial structures that exhibit characteristics not found in nature. It is possible to obtain a
metamaterial by combining artificial structures periodically. We investigated the unique
properties of Split Ring Resonators, High impedance Surfaces and Frequency Selective
Surfaces and composite metamaterials. We have successfully demonstrated the practical use
of these structures in antennas and circuits. We experimentally confirmed that composite
metamaterial can improve the performance of the structures considered in this thesis, at the
frequencies where electromagnetic band gap transmission takes place
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Aquino, Manoel do Bonfim Lins de. "Antena de microfita com substrato metamaterial." Universidade Federal do Rio Grande do Norte, 2008. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15224.
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Previous issue date: 2008-11-19<br>Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior<br>This paper presents a theoretical and numerical analysis of the parameters of a rectangular microstrip antenna with metamaterial substrate. The metamaterial (MTM) theory was applied along with Transverse Transmission Line (LTT) method to characterize substrate quantities and obtain the general equations of the electromagnetic fields. A study on metamaterial theory was conducted to obtain the constructive parameters, which were characterized through permittivity and permeability tensors to arrive at a set of electromagnetic equations. Electromagnetic principes are used to obtained parameters such as complex resonance frequency, bandwidth and radiation pattern were then obtained. Different metamaterial and antenna configurations were simulated to miniaturize them physically and increase their bandwidth, the results of which are shown through graphics. The theoretical computational analysis of this work proved to be accurate when compared to other studies, and may be used for other metamaterial devices. Conclusions and suggestions for future work are also proposed<br>Este trabalho apresenta a an?lise te?rica e num?rica dos par?metros de uma antena de microfita tipo patch retangular sobre substrato metamaterial. Para isso, ? aplicada a teoria de metamateriais - MTM, em conjunto com o 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. ? realizado um estudo acerca da teoria de metamateriais com o intuito de obter seus par?metros construtivos, os mesmos s?o caracterizados atrav?s de tensores permissividade e permeabilidade. Essa teoria ? aplicada ao m?todo da Linha de Transmiss?o Transversa chegando-se ?s equa??es gerais para os campos eletromagn?ticos da antena. Em seguida s?o utilizados princ?pios da teoria eletromagn?tica para obter-se caracter?sticas como: freq??ncia de resson?ncia complexa, diagramas de radia??o e largura de banda. S?o simulados diferentes configura??es de metamateriais e antenas com o intuito de miniaturizar 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?rica computacional deste trabalho se mostra precisa, em compara??o a outros, podendo ser empregado em dispositivos que utilizem metamateriais como substratos. Ao final s?o apresentadas conclus?es e sugest?es para trabalhos futuros
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Lei, Qin. "All dielectric composites for metamaterial applications." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:2dd643a5-7590-44a2-833a-148ffaa655f6.
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This thesis describes my work on manufacturing of all dielectric polymer/ceramic composites for electromagnetic property customisation at microwave frequencies. Electromagnetic wave manipulation can be achieved with the help of transformation optics concept and metamaterials with desired permittivity and permeability properties. The use of all-dielectric metamaterials, in particular, offers a novel solution to broadband, low loss microwave devices. In this work, polymer/ceramic composites were studied to provide materials with a wide range of permittivity that can be customised precisely by optimised manufacturing routes. Thermoplastic perfluoroalkoxy (PFA) and thermoset epoxy were mainly used as polymer matrices and ferroelectric powders such as barium titanate used as ceramic fillers. Different composite types were fabricated by spraying, casting and 3D printing, with each manufacturing method carefully studied to produce stable and uniform composite quality. The microstrcutures of these composites were examined by microtomy and SEM and the dielectric properties were assessed by impedance and waveguide measurements for difference microwave frequency ranges. Controllable dielectric constants from 3 to 18 with high accuracy in epoxy/BT composites were achieved at 12 - 18 GHz. These composites were then used to fabricate advanced microwave devices such as the power divider lens to demonstrate my capability of permittivity customisation. Simulations for these advanced applications were done in Comsol Multiphysics and were compared to the experimental results.
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Maassel, Michael. "A Metamaterial-Based Multiband Phase Shifter." Diss., North Dakota State University, 2014. https://hdl.handle.net/10365/27095.
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A design methodology for a multi-band phase shifter using a metamaterial-based transmission line was developed. This method is different in that the loaded-line phase shifter has a phase shift of 90 degrees at the center frequencies of both bands instead of -90 degrees and -270 degrees. The method was validated using simulation and measured results.
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Ijaz, Bilal. "Metamaterial-Inspired Reconfigurable Series-Fed Arrays." Diss., North Dakota State University, 2014. https://hdl.handle.net/10365/27593.
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One of the biggest challenges in modern day wireless communication systems is to attain agility and provide more degrees of freedom in parameters such as frequency, radiation pattern and polarization. Existing phased array antenna technology has limitations in frequency bandwidth and scan angle. So it is important to design frequency reconfigurable antenna arrays which can provide two different frequency bandwidths with a broadside radiation pattern having a lower sidelobe and reduced frequency scanning. The reconfigurable antenna array inspired by the properties of metamaterials presented here provides a solution to attain frequency agility in a wireless communication system. The adaptive change in operating frequency is attained by using RF p-i-n diodes on the antenna array. The artificially made materials having properties of negative permeability and negative permittivity have antiparallel group and phase velocities, and, in consequence of that, they support backward wave propagation. The key idea of this work is to demonstrate that the properties of metamaterial non-radiating phase shifting transmission lines can be utilized to design a series-fed antenna array to operate at two different frequency bands with a broadside radiation pattern in both configurations. In this research, first, a design of a series-fed microstrip array with composite right/left-handed transmission lines (CRLH-TLs) is proposed. To ensure that each element in the array is driven with the same voltage phase, dual-band CRLH-TLs are adopted instead of meander-line microstrip lines to provide a compact interconnect with a zero phase-constant at the frequency of operation. Next, the work is extended to design a reconfigurable series-fed antenna array with reconfigurable metamaterial interconnects, and the expressions for array factor are derived for both switching bands.
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Venkatakrishnan, Rajiv Krishnan. "Compact Metamaterial UHF RFID Tag Antennas." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1313767918.
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Noor, Adnan. "Metamaterial electromagnetic absorbers and plasmonic structures." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/metamaterial-electromagnetic-absorbers-and-plasmonic-structures(7028ac57-86c2-4557-8f57-1acb03ee8800).html.
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In this thesis metamaterial radar absorbers and plasmonic structures have been investigated. Following a brief overview covering metamaterial structures, and their applications in various areas of Microwave Engineering, a novel thin metamaterial wideband radar absorber, formed by two layers of resistive Hilbert curve arrays, is proposed and analysed numerically in HFSS, revealing a reduction in Monostatic Radar Cross Section (RCS) of more than 10 dB from 9.1 to 18.8 GHz (70% fractional bandwidth) for both polarizations. The structure has thickness of only 0.11λ to 0.24λ at lowest and highest frequencies respectively. The lateral dimensions are only 0.13λ to 0.3λ per unit cell at lowest and highest frequencies respectively which is several times smaller than that of recently reported circuit analogue absorbers operating in the similar frequency band. Furthermore, a wideband terahertz Hilbert curve array is proposed and analyzed both theoretically and numerically, showing an absorption bandwidth of more than one octave. This was followed by study of plasmonic cloak for subwavelength conducting objects. It was demonstrated that a plasmonic cloak designed for a conducting sphere will work for non spherical conducting objects of similar dimensions as well. Finally spoof plasmonic structures were investigated. A novel plasmonic structure based on a modified Apollonian fractal array of cylindrical coaxial apertures in an aluminium sheet was proposed and analyzed. The structure exhibits negative group velocity with less than 3.5 dB attenuation. Plasmonic structure based on Sierpinski array of apertures was also investigated and found to give quite good extraordinary transmission bandwidth.
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Hao, Jianping. "Broad band electromagnetic perfect metamaterial absorbers." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10076/document.
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Ce travail de thèse concerne les structures artificielles à base de métamatériaux permettant la réalisation d’absorbants parfaits. Après une brève introduction des métamatériaux, de leur fonctionnement en tant qu’absorbants et de l’état de l’art, quatre types de structures fonctionnant en bandes centimétrique ou millimétrique ont été conçus puis fabriqués à savoir (i) des réseaux de cubes BaSrTiO3 (BST) basés sur les résonances de Mie, (ii) des réseaux désordonnés composés d’anneaux métalliques mettant en jeu des effets de résonance semblables aux systèmes plasmoniques (iii) des absorbants à quatre résonateurs élémentaires sur substrat flexible et (iv) des réseaux multicouches métal-diélectrique de forme pyramidale. Pour l’ensemble, des simulations numériques, corroborées par l’expérience en guide d’onde ou en espace libre, montrent l’existence d’un moment magnétique. Celui-ci est induit par une boucle des courants de déplacement et de conduction. Pour les structures périodiques, les conditions de grande largeur de bande d’absorption ont été établies sur la base du piégeage et de la dissipation de l’énergie incidente. Pour les réseaux désordonnés, il est montré le rôle capital des couplages entre résonateurs. Des structures périodiques à base de ferroélectrique de dimensions sous longueur d’onde ont été assemblées avec succès tandis que des absorbants flexibles ont été réalisés par technique d’impression jet d’encre montrant l’amélioration d’un facteur quatre de la bande d’absorption. Des améliorations comparables ont été obtenues à l’aide de réseaux d’anneaux, dont les positions dans le plan sont désordonnées, résultant de la distribution des fréquences de résonance par effet de couplage fort entre les résonateurs<br>In this thesis broadband Metamaterial Perfect Absorbers (MPAs) have been investigated. Following a brief introduction of metamaterials, operating mechanisms and state of the art of MPA, four absorber types operating either at centimeter or millimeter wavelengths have been designed and fabricated namely :(i) Mie-resonance based BaSrTiO3 (BST) arrays operating at microwaves, (ii) plasmonic-type disordered ring-shaped MPA, (iii) four patches millimeter wave flexible absorbers (iv) Pyramidal metal/dielectric stacked resonator arrays. For all the structures, it was demonstrated, through numerical simulations, assessed by characterization in a waveguide configuration or in free space, that unit absorbance relies on magnetic resonances induced by a current loop combining displacement and conduction currents. For periodic arrays, the condition for a broad band operation was established via the optimization of dissipation and trapping of electromagnetic energy in the resonators. For disordered metamaterials, it was shown the major role played by the magnetic dipole-dipole interaction. From the technological side, Ferroelectrics cube arrays with subwavelength dimensions were assembled onto a metal plate while flexible multi-resonators periodic arrays were successfully fabricated by ink-jet printing showing a fourfold enhancement of the absorbance bandwidth thanks to the overlapping of resonance frequencies. Comparable improvement in the bandwidth was also pointed out with randomly position metal ring arrays due to the distribution of resonance frequencies that result from tight in-plane resonator coupling
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Heffernan, Travis Jade. "Metamaterial Enhanced Wireless Power Transmission System." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1069.
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Nikolai Tesla's revolutionary experiments demonstrated the possible benefits of transmitting power wirelessly as early as 1891. Applications for the military, consumers, emergency personnel, remote sensors, and others use Tesla’s discovery of wireless power. Wireless power transmission (WPT) has the potential to be a common source of consumable energy, but it will only receive serious consideration if the transmit and receive systems are extremely efficient and capable of delivering usable amounts of power. Research has been conducted to improve the efficiency and performance of nearly every aspect of WPT systems, but the relatively new field of metamaterials (MTMs) has yet to play a dominate role in improving system performance. A gradient index (GRIN) MTM lens was designed using Ansoft’s High Frequency Structure Simulator (HFSS) to improve antenna gain and thereby increase WPT system performance. A simple WPT demonstration system using microstrip patch antennas (MPAs) confirmed the benefits of the GRIN MTM lens. The WPT demonstration system, MPAs, and GRIN MTM lens were constructed and experimentally tested near 2.45 GHz. The theoretical and experimental gain improvement of the MPA due to the GRIN MTM lens is 5.91 dB and 7.06 dB, respectively.
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King, Neil James. "Aspects of metamaterial structures : theory and simulation." Thesis, University of Salford, 2007. http://usir.salford.ac.uk/26761/.
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The investigations reported here address the issue of overcoming loss in a typical isotropic metamaterial. The possibility of adding functionality to such materials, through gyrotropic effects, and diffraction management of nonlinear beams, driven by negative phase accumulation, is presented. Loss is overcome by the introduction of gain to the metamaterial. This is achieved on the basis that typical split-ring metaparticles can be suitably enhanced through the addition of carefully selected diodes. The detailed analysis given here deploys a familiar equivalent circuit model and specific current-voltage characteristics. It is emphasised that conditions must be in place to ensure overall stable material behaviour. The methodology uses convective and absolute instability concepts and it is shown that the latter can be so detrimental as to lead to a much reduced frequency window of operation. Another set of investigations emphasises that surface waves provide a path to new science. Consequently the propagation of surface waves along the interface between a metamaterial and a gyrotropic medium is promising for applications. The investigation outcomes of this complicated system need to demonstrate generation properties in real time. Hence, some unique finite-difference time-domain (FDTD) computations have been developed enabling their interesting connection to the Goos- Hanchen shift to be elegantly displayed. Many interesting forms of surface waves are discussed including the simultaneous generation of TE and TM waves propagating in opposite directions. It is well known that in an isotropic metamaterial backward waves can exist so this property is exploited to create a fascinating form of diffraction management. This is investigated both for the bulk and for cavities and the impact of what is defined as nonlinear diffraction is introduced. Finally, some magnetooptics is introduced that adds even more functionality to the generation of cavity solitons.
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Lee, Yoonjae. "Design and Analysis of Metamaterial-based Antennas." Thesis, Queen Mary, University of London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518264.
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Ash, Benjamin James. "Locally resonant metamaterial for surface acoustic waves." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34380.
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The control of surface acoustic waves (SAWs) using arrays of annular holes was investigated both experimentally and through numerical modelling. Periodic elastic composites, phononic crystals (PnCs), were designed using these annular holes as constituent elements. Local resonances associated with the annular hole structure were found to induce phonon bandgaps of a highly frequency tailorable nature, at frequencies where radiation of acoustic energy into the bulk of the substrate medium is avoided. These bandgaps are numerically demonstrated to exhibit order-of-magnitude improved extinction ratios for finite numbers of PnC elements, relative to the commonly used cylindrical pillar architecture. Devices fabricated on commercially available lithium niobate SAW delay lines verify the predicted behaviour. Through laser knife-edge detector vibrometry, a bandgap attenuation of 24.5 dB at 97 MHz was measured, in excellent agreement with finite element method (FEM) simulations. The first reported experimental evidence of subwavelength confinement of propagating SAWs was realised using the same annular hole PnC concept. Defect holes of perturbed resonant frequencies are included within the PnC to define waveguides and cavities. Confinement within these defects was demonstrated to occur at subwavelength frequencies which was experimentally observed in fabricated cavities using standard SAW transducers, as measured by laser Doppler vibrometry. The success of this result was attributed to the impedance matching of hybridised modes to Rayleigh SAWs in un-patterned substrates at the defect resonance. The work here has the potential to transform the field by providing a method to enhance SAW interactions, which is a route towards the realisation of many lab-on-chip applications. Finally, the use of annular hole arrays as negative refraction metamaterials was investigated. The symmetry was broken of the unit cells by alternating either the locally resonant frequencies or the distance separating the constituent elements. Both methods, called the bi-dispersive and bi-periodic methods, were numerically demonstrated to exhibit negative group velocity bands within the first Brillouin zone. Preliminary experimental results show that the design has the potential to be used in superlensing, where a SAW spot was imaged over a subwavelength flat lens. Future research looks to demonstrate that this result can be attributed to negative refraction.
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Gao, Xiang. "Antenna designs based on metamaterial-inspired structures." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7240/.
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The research presented in this thesis concerns antenna designs based on metamaterial-inspired structures. Based on a review of the existing literature and understanding of the background theories, different metamaterial-inspired structures are applied to designs of resonant antennas (RAs) and leaky wave antennas (LWAs) for improved antenna characteristics. Extended composite right/left-handed (ECRLH) unit cell structures enable the RA designs with multiband or wideband properties; the novel metamaterial-inspired supercell structures enable the LWA designs with the dual-passband property and the backward-to-forward leaky-wave radiation characteristics in each passband. In addition, two tunable antennas are presented to mainly achieve the frequency reconfigurability and possibly the pattern reconfigurability by electronically controlling surface-mounted semiconductor varactors or discrete ferroelectric barium strontium titanium (BST) thin-film varactors. Furthermore, the uncertainty analysis in determination of permittivity of BST film materials from the characterization process is discussed in this thesis, in order to provide the design clues when the antenna with BST materials is designed. The conclusions are drawn and the possible future research directions are explained as well.
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Alburaikan, Abdullah. "Metamaterial structure inspired miniature RF/microwave filters." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/metamaterial-structure-inspired-miniature-rfmicrowave-filters(5e1dee93-038a-42ef-99ad-669ecc4b4763).html.
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Novel feedback signal interference concept for bandpass filter (BPF) design is proposed in this thesis. This new concept was utilized to design wide stopband BPF with superior performance for WLAN applications. The proposed filtering structure consists of two simple coupled-line couplers. The first coupler was employed within the main signal path and the second coupler which is open circuited at the opposite ends was used for the feedback circuit. This new filtering structure was fabricated using low temperature co-fired ceramic technology. The fabricated BPF exhibits an insertion loss (IL) of -1.3 dB with a 3dB fractional bandwidth of 13% at a centre frequency of 2.4 GHz. Furthermore, an attenuation level of -15 dB is achieved up to 4.7fo. Using stepped impedance coupled-lines in the feedback; the stopband performance of the proposed structure can be significantly improved while keeping passband performance intact. Furthermore, the feedback signal interference concept proved to be versatile and can be used to design high selectivity microstrip BPF using composite right/left handed transmission line unit cell in the feedback circuit. The measured results show that roll-up/down rate of more than 300 dB/GHz can be achieved with low IL.The spectrum based quality factor for CRLH TL based BPF is explored and thoroughly studied in this thesis to design a low phase noise oscillator. The proposed metamaterial BPF has higher spectrum based quality factor within the left-handed region due to the slow-wave propagation. This intriguing feature enables the design of a free-running oscillator with excellent phase noise performance operating at a frequency of 2.05 GHz. The fabricated oscillator demonstrates a phase noise of -126.7 dBc/Hz at 100 kHz frequency offset and a FOM of -207.2 dBc/Hz at a 1 MHz frequency offset, being one of the very best reported so far. Many microstrip multi-band BPF design techniques are presented in the literature that offers superior performance in terms of IL, 3dB FBW, and high selectivity. These methods mainly lack the ability to obtain high performance with compact size. Coupled slotted open stubs are used to design a miniaturized dual-wideband BPF. Interdigital capacitor and inner open stubs are used to improve rejection level within the stopbands and increase selectivity. The measurement results reveal that the fabricated dual-wideband BPF has two passbands with a 3dB FBW of 117% and 36%, at respective centre frequencies of 1 GHz and 6.65 GHz. The filter has a super compact size (0.09 Gammag × 0.05 Gammag) where Gammag denotes the guided wavelength at the centre frequency of the first passband and exhibits an attenuation level greater than 20 dB up to 12 GHz.
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Escorcia, Carranza Ivonne. "Metamaterial based CMOS terahertz focal plane array." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6955/.
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The distinctive properties of terahertz radiation have driven an increase in interest to develop applications in the imaging field. The non-ionising radiation properties and transparency to common non-conductive materials have led research into developing a number of important applications including security screening, medical imaging, explosive detection and wireless communications. The proliferation of these applications into everyday life has been hindered by the lack of inexpensive, compact and room-temperature terahertz sources and detectors. These issues are addressed in this work by developing an innovative, uncooled, compact, scalable and low-cost terahertz detector able to target single frequency imaging applications such as stand-off imaging and non-invasive package inspection. The development of two types of metamaterial (MM) based terahertz focal plane arrays (FPAs) monolithically integrated in a standard complementary metal-oxide semiconductor (CMOS) technology are presented in this Thesis. The room temperature FPAs are composed of periodic cross-shaped resonant MM absorbers, microbolometer sensors in every pixel and front-end readout electronics fabricated in a 180 nm six metal layer CMOS process from Texas Instruments (TI). The MM absorbers are used due to the lack of natural selective absorbing materials of terahertz radiation. These subwavelength structures are made directly in the metallic and insulating layers available in the CMOS foundry process. When the MM structures are distributed in a periodic fashion, they behave as a frequency-selective material and are able to absorb at the required frequency. The electromagnetic (EM) properties are determined by the MM absorber geometry rather than their composition, thus being completely customisable for different frequencies. Single band and broadband absorbers were designed and implemented in the FPAs to absorb at 2.5 THz where a natural atmospheric transmission window is found, thus reducing the signal loss in the imaging system. The new approach of terahertz imaging presented in this Thesis is based in coupling a MM absorber with a suitable microbolometer sensor. The MM structure absorbs the terahertz wave while the microbolometer sensor detects the localised temperature change, depending on the magnitude of the radiation. Two widely used microbolometer sensors are investigated to compare the sensitivity of the detectors. The two materials are Vanadium Oxide (VOx) and p-n silicon diodes both of which are widely used in infrared (IR) imaging systems. The VOx microbolometers are patterned above the MM absorber and the p-n diode microbolometers are already present in the CMOS process. The design and fabrication of four prototypes of FPAs with VOx microbolometers demonstrate the scalability properties to create high resolution arrays. The first prototype consists of a 5 x 5 array with a pixel size of 30 μm x 30 μm. An 8 x 8 array, a 64 x 64 array with serial readout and a 64 x 64 array with parallel readout are also presented. Additionally, a 64 x 64 array with parallel output readout electronics with p-n diode microbolometers was fabricated. The design, simulation, characterisation and fabrication of single circuit blocks and a complete 64 x 64 readout integrated circuit is thoroughly discussed in this Thesis. The absorption characteristics of the MMs absorbers, single VOx and p-n diode pixels, 5 x 5 VOx FPA and a 64 x 64 array for both microbolometer types demonstrate the concept of CMOS integration of a monolithic MM based terahertz FPA. The imaging performance using both transmission and reflection mode is demonstrated by scanning a metallic object hidden in a manila envelope and using a single pixel of the array as a terahertz detector. This new approach to make a terahertz imager has the advantages of creating a high sensitivity room temperature technology that is capable of scaling and low-cost manufacture.
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Reza, Arvin. "The optical properties of metamaterial waveguide structures." Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1573.
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Zedler, Michael. "Systematic topological design of metamaterials : scalar and vectorial 3D metamaterials and their realisation." kostenfrei, 2008. http://mediatum2.ub.tum.de/doc/653119/653119.pdf.
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Jan, Naeem A. "Anomalous Nature Of Metamaterial Inclusion and Compact Metamaterial-Inspired Antennas Model For Wireless Communication Systems. A Study of Anomalous Comportment of Small Metamaterial Inclusions and their Effects when Placed in the Vicinity of Antennas, and Investigation of Different Aspects of Metamaterial-Inspired Small Antenna Models." Thesis, University of Bradford, 2017. http://hdl.handle.net/10454/16003.
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Metamaterials are humanly engineered artificial electromagnetic materials which produce electromagnetic properties that are unusual, yet can be observed readily in nature. These unconventional properties are not a result of the material composition but rather of the structure formed. The objective of this thesis is to investigate and design smaller and wideband metamaterial-inspired antennas for personal communication applications, especially for WiMAX, lower band and higher band WLAN applications. These antennas have been simulated using HFSS Structure Simulator and CST Microwave Studio software. The first design to be analysed is a low-profile metamaterial-inspired CPW-Fed monopole antenna for WLAN applications. The antenna is based on a simple strip loaded with a rectangular patch incorporating a zigzag E-shape metamaterial-inspired unit cell to enable miniaturization effect. Secondly, a physically compact, CSRR loaded monopole antenna with DGS has been proposed for WiMAX/WLAN operations. The introduction of CSRR induces frequency at lower WLAN 2.45 GHz band while the DGS has provided bandwidth enhancement in WiMAX and upper WLAN frequency bands, keeping the radiation pattern stable. The next class of antenna is a compact cloud-shaped monopole antenna consisting of a staircase-shaped DGS has been proposed for UWB operation ranges from 3.1 GHz to 10.6 GHz. The novel shaped antenna along with carefully designed DGS has resulted in a positive gain throughout the operational bandwidth. Finally, a quad-band, CPW-Fed metamaterial-inspired antenna with CRLH-TL and EBG is designed for multi-band: Satellite, LTE, WiMAX and WLAN.
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Mbomson, Ifeoma Grace. "Mid-infrared photonic sensors based on metamaterial structures." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7462/.
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In this work three different metallic metamaterials (MMs) structures such as asymmetric split ring resonators (A-SRRs), dipole and split H-shaped (ASHs) structures that support plasmonic resonances have been developed. The aim of the work involves the optimization of photonic sensor based on plasmonic resonances and surface enhanced infrared absorption (SEIRA) from the MM structures. The MMs structures were designed to tune their plasmonic resonance peaks in the mid-infrared region. The plasmonic resonance peaks produced are highly dependent on the structural dimension and polarisation of the electromagnetic (EM) source. The ASH structure particularly has the ability to produce the plasmonic resonance peak with dual polarisation of the EM source. The double resonance peaks produced due to the asymmetric nature of the structures were optimized by varying the fundamental parameters of the design. These peaks occur due to hybridization of the individual elements of the MMs structure. The presence of a dip known as a trapped mode in between the double plasmonic peaks helps to narrow the resonances. A periodicity greater than twice the length and diameter of the metallic structure was applied to produce narrow resonances for the designed MMs. A nanoscale gap in each structure that broadens the trapped mode to narrow the plasmonic resonances was also used. A thickness of 100 nm gold was used to experimentally produce a high quality factor of 18 in the mid-infrared region. The optimised plasmonic resonance peaks was used for detection of an analyte, 17β-estradiol. 17β-estradiol is mostly responsible for the development of human sex organs and can be found naturally in the environment through human excreta. SEIRA was the method applied to the analysis of the analyte. The work is important in the monitoring of human biology and in water treatment. Applying this method to the developed nano-engineered structures, enhancement factors of 10^5 and a sensitivity of 2791 nm/RIU was obtained. With this high sensitivity a figure of merit (FOM) of 9 was also achieved from the sensors. The experiments were verified using numerical simulations where the vibrational resonances of the C-H stretch from 17β-estradiol were modelled. Lastly, A-SRRs and ASH on waveguides were also designed and evaluated. These patterns are to be use as basis for future work.
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Shahbazali, Maryam, and Wael Baki. "Influence of disorder on microwave left-handed metamaterial." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-19099.
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Shelley, Samuel. "The control of fluid flow using metamaterial concepts." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34636.
Full textAbstract:
The work presented in this thesis concerns the application of concepts that are widely used in metamaterial research to the control of fluid flow. In particular surface structuring and resonance were investigated. The initial work focussed on Stokes flow over structured surfaces. The effective boundary conditions that the structuring creates, analogous to the impedance boundary condition encountered in electromagnetism and acoustics, were examined. Exact solutions for the flow and slip length along the grooves of a family of surfaces were derived. These were compared to Finite Element Method (FEM) models and previous work valid for arbitrary structured surfaces, which was based on a perturbation expansion. Good agreement was found for all available surfaces. The previously presented solution was then also compared to results for a sinusoidal surface, finding good agreement for low aspect ratios but diverging at intermediate aspect ratios. Extending the perturbation theory beyond first order was found to improve the agreement. To explore the concept of resonance in fluid dynamics laminar flow around a circular bluff body with an attached flexible tail was considered, investigating how the resonant behaviour of the elastic tail modified the drag and vortex shedding frequency of the body. The results were compared against the no tail case as well as a rigid tail. For short tail lengths the average drag was reduced compared to both reference cases, whilst the vortex shedding could be either enhanced or reduced. When one of the resonant frequencies of the tail matched the vortex shedding frequency of the body, the resonance motion of the tail resulted in in sharp changes to both the drag and vortex shedding frequency. In the finally section of the thesis I describe the Particle Image Velocimetry experiments that were set up to verify the resonant flexible tail behaviour. The process by which the initial set up was upgraded is given. Results are shown for a circular bluff body being towed through the fluid. This is then extended to a circular bluff body with an attached rigid tail. Preliminary results for the flexible tail case are then presented.
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Sousa, Neto Marinaldo Pinheiro de. "Um estudo de metamaterial em antenas de microfita." Universidade Federal do Rio Grande do Norte, 2014. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15247.
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Previous issue date: 2014-04-25<br>Universidade Federal do Rio Grande do Norte<br>Metamaterials have attracted a great attention in recent years mostly due to their electromagnetic properties not found in nature. Since metamaterials began to be synthesized by the insertion of artificially manufactured inclusions in a medium specified host , it provides the researcher a broad collection of independent parameters such as the electromagnetic properties of the material host. In this work was presents an investigation of the unique properties of Split Ring Resonators and compounds metamaterials was performed. We presents a theoretical and numerical analysis , using the full-wave formalism by applying the Transverse Transmission Line - LTT method for the radiation characteristics of a rectangular microstrip antenna using metamaterial substrate, as is successfully demonstrated the practical use of these structures in antennas. We experimentally confirmed that composite metamaterial can improved the performance of the structures considered in this thesis<br>Os metamateriais tem atra?do uma grande aten??o nas ?ltimas d?cadas, principalmente devido as suas propriedades eletromagn?ticas n?o encontradas na natureza. Desde que os metamateriais passaram a ser sintetizados atrav?s da inser??o de inclus?es artificialmente fabricadas num meio hospedeiro especificado, isto propicia ao pesquisador uma larga cole??o de par?metros independentes, tais como as propriedades eletromagn?ticas do material hospedeiro. Neste trabalho foi realizada uma investiga??o das propriedades ?nicas dos Ressoadores em Anel Partido (Split Ring Ressonators - SRR) e dos metamateriais compostos. Apresentou-se uma an?lise te?rica e num?rico-computacional, utilizando o formalismo de onda completa atrav?s da aplica??o do m?todo da Linha de Transmiss?o Transversa LTT, para as caracter?sticas ressonantes de uma antena de microfita com patch retangular utilizando substrato metamaterial, assim como ? demonstrado com sucesso ? utiliza??o pr?tica dessas estruturas em antenas. Esta utiliza??o pr?tica ? confirmada experimentalmente
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Sousa, Neto Marinaldo Pinheiro de. "Caracteriza??o de antenas planares com substrato metamaterial." Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15376.
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Previous issue date: 2011-11-25<br>Universidade Federal do Rio Grande do Norte<br>This work presents a theoretical and numerical analysis for the radiation
characteristics of rectangular microstrip antenna using metamaterial substrate. The full
wave analysis is performed in the Fourier transform domain through the application of
the Transverse Transmission Line - TTL method. A study on metamaterial theory was
conducted to obtain the constructive parameters, which were characterized through
permittivity and permeability tensors to arrive at a set of electromagnetic equations. The
general equations for the electromagnetic fields of the antenna are developed using the
Transverse Transmission Line - TTL method. Imposing the boundary conditions, the
dyadic Green s function components are obtained relating the surface current density
components at the plane of the patch to the electric field tangential components. Then,
Galerkin s method is used to obtain a system of matrix equations, whose solution gives
the antenna resonant frequency. From this modeling, it is possible to obtain numerical
results for the resonant frequency and return loss for different configurations and
substrates<br>Esta disserta??o de Mestrado apresenta uma an?lise te?rica e num?ricocomputacional,
das caracter?sticas ressonantes de uma antena de microfita com patch
retangular utilizando substrato metamaterial. A an?lise utiliza o formalismo de onda
completa atrav?s da aplica??o do m?todo da Linha de Transmiss?o Transversa - LTT,
no dom?nio da transformada de Fourier. ? realizado um estudo acerca da teoria dos
metamateriais com o intuito de obter seus par?metros construtivos, os mesmos s?o
caracterizados atrav?s de tensores permissividade e permeabilidade. As equa??es gerais
para os campos eletromagn?ticos da antena s?o desenvolvidas aplicando o m?todo da
Linha de Transmiss?o Transversa - LTT. A imposi??o das condi??es de contorno
adequada ? estrutura permite determinar as fun??es di?dicas de Green, relacionando as
componentes da densidade de corrente no patch com as componentes tangenciais do
campo el?trico. O m?todo de Galerkin ? ent?o usado para obter a equa??o matricial,
cuja solu??o n?o trivial fornece a freq??ncia de resson?ncia da antena. A partir da
modelagem ? poss?vel obter resultados para a freq??ncia de resson?ncia em diferentes
configura??es de antenas e substratos, al?m da perda de retorno
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Watson, Derek Wesley. "Collective scattering of subwavelength resonators in metamaterial systems." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/416581/.
Full textAbstract:
In this thesis, we model the electromagnetic (EM) interactions between plasmonic resonators and an incident EM field. By capturing the fundamental physics of each resonator, such as its resonance frequency and radiative decay rate, the dynamics of the EM interactions can be modeled by a linear set of equations. The system's eigenmodes exhibit characteristic line shifts and linewidths that may be subradiant or superradiant. For simple resonator systems, we approximate each resonator as a point electric dipole. Nanorods and nanobars, are such resonators where the magnetization can be assumed to be negligible. However, closely spaced parallel electric dipoles can exhibit EM properties similar to higher order multipoles, e.g., electric quadrupoles. We show how, in an original way, simple systems comprising closely spaced parallel pairs of electric dipoles can be approximated as electric quadrupole and magnetic dipole resonators. When the resonators are close, their finite-size and geometry is important to the EM interactions, and we show how we cope with these important factors in our model. We analyze in detail a nanorod configuration comprising pairs of plasmonic nanorods - a toroidal metamolecule, and show how the elusive toroidal dipole moment appears as a radiative eigenmode. In this original work, we find that the radiative interactions in the toroidal metamolecule can be qualitatively represented by our point electric dipole approximation and finite-size resonator model. The results demonstrate how the toroidal dipole moment is subradiant and difficult to excite by incident light. By means of breaking the geometric symmetry of the metamolecule, we show the toroidal mode can be excited by linearly polarized light and that it appears as a Fano resonance dip in the forward scattered light. We provide simple optimization protocols for maximizing the toroidal dipole mode excitation. This opens up possibilities for simplified control and driving of metamaterial arrays consisting of toroidal dipole unit-cell resonators.
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Odabasi, Hayrettin. "Novel Metamaterial Blueprints and Elements for Electromagnetic Applications." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366281874.
Full text
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Ziolkowski, Richard W. "Passive and active metamaterial-inspired nano-scale antennas." IEEE, 2016. http://hdl.handle.net/10150/623141.
Full textAbstract:
A variety of open and closed multi-layered nanoparticle structures have been considered analytically and numerically for their use as scatterers and radiators. These include metamaterial-inspired structures based on dielectrics and metals excited by either plane waves or electric Hertzian dipoles at optical frequencies. Both passive and active (gain impregnated dielectric) materials have been considered. Enhanced and mitigated scattering and radiating effects have been modeled. Nano-antenna and nano-amplifier configurations for optical applications have been emphasized. A review of these modeling efforts will be presented.
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Grigoleto, Hayashi Juliano. "Wire Array Infrared Metamaterial Fibres: Fabrication and Applications." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17790.
Full textAbstract:
Metamaterials are artificial composite materials that exhibit exotic properties due to their components and sub-wavelength structure. During the past decades, several new materials have emerged from this research field with exciting new optical properties and applications. However, the fabrication of certain meta-structures remains a challenge, particularly with low cost and in large volumes. Fibre drawing is an attractive alternative to overcome such problems, but currently fabrication constraints restrict the size of the metal/dielectric drawn structures, limiting their operation to THz frequencies. In this context, this thesis concerns the fabrication, characterization, and use of new soft-glass based wire array metamaterials fibres for applications in the infrared. Numerical modelling of wire array structures is presented to understand which material combinations and structural parameters are more appropriate for infrared metamaterial fibres. The co-drawing process used is described, focusing on the adaptations used to minimize fluctuation of the structure due to fluid dynamics. Metamaterial fibres with uniform structures containing wire diameter and spacing on the order of few hundreds of nm are produced, which are compatible with operation at mid-infrared frequencies. The fabrication of metamaterial fibre tapers with steep transitions, generating hyperlenses, is also demonstrated. Far field imaging is attempted and the challenges regarding subdiffraction imaging are discussed. Feasible alternatives for future far field super-resolution imaging are proposed based on our numerical modelling and the typical structural transitions fabricated. Since the operational range of our hyperlenses is not limited to the infrared, subdiffraction focusing of 1/176 of the operational wavelength is reported at THz frequencies, achieved by combining a polymer hyperlens with our new infrared hyperlens.
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Jin, Peng. "IMPROVING THE PERFORMANCE OF ANTENNAS WITH METAMATERIAL CONSTRUCTS." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/193567.
Full textAbstract:
Metamaterials (MTMs) are artificial materials that can be designed to have exotic properties. Because their unit cells are much smaller than a wavelength, homog-enization leads to effective, macroscopic permittivity and permeability values that can be used to determine the MTM behavior for applications. There are four possible combinations of the signs of permittivity and permeability values. The desired choice of sign depends on the particular application. Inspired by these MTM concepts, several MTM-inspired structures are adopted in this dissertation to improve various performance characteristics of several different classes of antennas. Three different metamaterial-inspired engineering approaches are introduced to achieve enhanced antenna designs. First,the transmission-line (TL) type of MTM is used to modify the dispersion characteristics of a log-periodic dipole array (LPDA) antenna. When LPDA antennas are used for wideband pulse applications, they suffer from severe frequency dispersionbecause the phase center location of each element is frequency dependent. By incorporating MTM-based phase shifters, the LPDA frequency dispersion properties are improved significantly. Both eight and ten element MTM-modified LPDA antennasare designed to enhance the fidelity of the resulting output pulses. Second, epsilon-negative unit cells are used to design several types of electrically small, resonant parasitic elements which, when placed in the very near field of a driven element, leadto nearly complete matching (i.e., reactance and resistance) of the resulting electrically small antenna system to the source and to an enhanced radiation efficiency. However, despite these MTM-inspired electrically small antennas being very efficient radiators, their bandwidth remains very narrow, being constrained by physicallimitations. Third, we introduce an active parasitic element to enhance the band-width performance of the MTM-inspired antennas. The required active parasitic element is derived and an implementation methodology is developed. Electricallysmall active Z, stub, and canopy antennas are designed. It is demonstrated that an electrically small antenna with ka around 0.046 and over a 10% bandwidth can be realized, in principle.
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Seren, Huseyin R. "Optically controlled metamaterial absorbers in the terahetz regime." Thesis, Boston University, 2014. https://hdl.handle.net/2144/12950.
Full textAbstract:
Thesis (Ph.D.)--Boston University<br>Electromagnetic wave absorbers have been intensely investigated in the last century and found important applications particularly in radar and microwave technologies to provide anechoic test chambers, or vehicle stealth. Adding new features such as dynamic modulation, absorption frequency tunability, and nonlinearity, absorbers gain further functions as spatial light modulators, adjustable protective layers, and saturable absorbers which was a key factor in creation of ultra-fast lasers. These efforts required a rigorous search on various materials to find desired behavior. As a rather recent research field Metamaterials (MM) provide an easier path for creation of such materials by allowing engineering the interaction between electromagnetic radiation and materials. Alongside many exotic applications such as invisibility cloaking or negative refraction, MMs also made perfect, or near-unity, absorbers possible. Thanks to their ability to control electric and magnetic responses, by matching the impedance of the MMs to that of free space and simultaneously increasing the losses in the structure, perfect absorption can be achieved. This has been experimentally demonstrated in various bands of electromagnetic spectrum such as microwave, terahertz (THz), infrared, and visible. As in their earlier counterparts, adding modulation and nonlinearity to MM absorbers will broaden their contribution especially in the THz region which is nascent in terms of optical devices such as switches, modulators or detectors. With the recent developments in the THz lasers, THz nonlinear absorbers will be needed to realize ultra-fast phenomena in this region. The main focus of this thesis is incorporating conventional and novel methods to create some of the initial examples of optically controlled MM THz perfect absorbers using microfabrication tools. [TRUNCATED]
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GARG, PRIYANKA. "DESIGN AND DEVELOPMENT OF METAMATERIAL BASED MICROWAVE COMPONENTS." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2020. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18774.
Full textAbstract:
Planar technology has gained a lot of popularity since its inception due to various advantages
it offered to the scientific world such as, light weight, compact size, ease of fabrication and
integration, suitability of mass production and compatibility with planar solid state devices.
However they also have certain drawbacks in terms of bandwidth, further miniaturization,
gain, efficiency, etc.
Metamataterials are introduced in the late 60s by a Russian physicist Victor Veselago [1],
which were further investigated by Pendry et. al. [2] and are an active area of research these
days. Metamaterials are the artificially engineered structures that offer extraordinary electromagnetic
properties not found in nature such as epsilon negative media (ENG), mu negative
media (MNG), double negative media (DNG), photonic band gap structures etc. They consist
of multiple unit cells whose dimensions are much smaller than l0/4, where l0 is the wavelength
corresponding to the highest frequency of operation, to achieve homogenization. It was
discovered that these materials alter the behaviour of electromagnetic waves in an unconventional
way leading to important phenomenon such as, reversal of Snells Law, Doppler effect
and Vavilov-Cerenkov radiation.
Due to the extraordinary behaviour of metamaterials they are used to improve the properties
of various planar devices and components which are discussed earlier. They can be used
to improve antenna’s gain, directivity, bandwidth and size, filter’s size, roll off, out of band
rejection levels and bandwidth. They are used for multiple frequency operation. They are
also being used for the development of super lenses, ultrathin perfect absorbers, cloaks, high
sensitivity and high resolution sensors, phase compensator etc. The main focus of this thesis
is on metamaterial based antennas, filters and absorbers.
Chapter 3 presents the design of a compact, low-profile, coplanar waveguide (CPW)-fed
metamaterial inspired dual band microstrip antenna for WLAN application. To achieve the
goal a triangular split ring resonator (TSRR) is used along with an open ended stub. The
proposed antenna has a compact size of 20×24 mm2 fabricated on an FR-4 epoxy substrate
with dielectric constant (er=4.4). The antenna provides two distinct bands I from 2.40-2.48
GHz and II from 4.7-6.04 GHz with reflection coefficient better than -10 dB, covering the
entire WLAN (2.4/5.2/5.8 GHz) band spectrum. The performance of this metamaterial inspired
antenna is also studied in terms of the radiation pattern, efficiency, and realized gain.
The antenna is practically fabricated and tested to show good agreement with the simulated
results.
Chapter 4 is divided into four sections. The first section presents a compact, low-profile
Band Stop Filter (BSF) designed using Complimentary Split Ring Resonator (CSRR). An
equivalent circuit model is also presented along with the simplified mathematical approach to
extract the parameters of the circuit model. This paper also presents the effect of variation
in the dimensions of split rings on characteristics of BSF. The proposed BSF has a compact
size of 27×20 mm2 designed on FR-4 substrate with dielectric constant (er)=4.3. The filter
provides complete suppression of the band at 2.4 GHz. The design and circuit analysis of this
metamaterial based filter is presented in terms of reflection coefficient, transmission coefficient
and impedance curve. The second section presents the design and analysis of a metamaterial
inspired Bandstop Filter (BSF) providing suppression of frequency at 3 GHz. The overall
size of proposed BSF is 20mm×20mm×1.6mm. Further,the extraction of lumped parameters
of the designed BSF using simulated results is presented and validation of the results using
equivalent circuit simulation is also presented. The third section presents a comparison based
study of microstrip transmission line based bandstop filters taking different complementary
resonators on the ground plane. Six metamaterial resonators unit cells have been investigated
from the literature. The dimensions are optimized to operate at 3 GHz and then their comparative
analysis is performed based on various properties of filters such as insertion loss, 3 dB
v
bandwidth, quality factor (Q), shape factor, overall size, unit cell size and group delay. There
are a number of metamaterial based resonators available in literature, so the objective of this
section of the chapter is to provide a comparative analysis so that the user can point out the
best configuration required while designing the bandstop filter that suits the desired specification
and also helps in developing the future ideas by taking into account the advantages of
the available structures. The forth section presents a compact, low-profile, Band Pass Filter
(BPF) based on balanced Dual Composite Right/Left Handed (D-CRLH) Transmission Line
(TL) is presented in this chapter. A balanced D-CRLH TL can be used to provide wideband
filter characteristics due to no frequency separation between the RH and LH frequency bands.
The proposed D-CRLH TL is designed using U-shaped complementary split ring resonator
(UCSRR). The extraction of equivalent circuit model of proposed UCSRR unit cell is also
performed. Further, the bandwidth of the proposed filter is enhanced by using the concept
of electric and magnetic coupling between the slot lines. The proposed via less BPF has a
compact size of 15×15 mm2 designed on an FR-4 substrate with dielectric constant(er)=4.3.
The design analysis of proposed bandpass filter is presented in terms of reflection coefficient,
transmission coefficient, impedance curve, propagation constant and group delay.
Chapter 5 presents a novel resonant metamaterial absorber exhibiting five resonant peaks
with absorptivity more than 90% in the range from S band to Ku band for radar cross-section
reduction and other FCC-airborne applications. The structure is designed on a low cost FR-4
substrate with 1 mm thickness which is equivalent to l /17.75 where l is the wavelength corresponding
to maximum resonant frequency of absorption, showing its ultrathin nature. The
fourfold symmetry of the design results in polarization insensitivity and provides an angular
stability up to 60◦ of incident angle. The multiband characteristics are obtained by combining
three different geometries in a single structure. Performance of the absorber is studied in
terms of absorptivity, material parameters, normalized impedance, polarization insensitivity
and oblique incidence. Finally, the design is fabricated on a 200×200mm2 FR-4 substrate and
measurements are performed. Further, the chapter also presents a closed meander line shaped
vi
metamaterial absorber operating at 3.5 GHz WiMAX band. The proposed metamaterial absorber
unit cell has a compact size of 0.11l0×0.11l0 design on an ultrathin FR-4 substrate
with thickness 0.018l0, where l0 is the wavelength corresponding to operating frequency.
The proposed absorber shows an absorptivity of 98.5 % at the intended frequency. The design
is evolved from a simple square loop to a symmetrical meander line structure whose dimensions
are optimized to operate at 3.5 GHz WiMAX band. An equivalent circuit model is also
defined to depict the electrical properties of the structure. The proposed design also shows
insensitivity to polarization as well as change in incident angle of the wave over a wide-angle
(upto 60◦) for both TE and TM polarization. The proposed structure is a good candidate for
radar cross section reduction of an antenna.
Chapter 6 demonstrates the use of metamaterial absorber (MA) to achieve high isolation
between two patch antennas in a 2-element MIMO system operating at 5.5 GHz resonant
frequency useful for WiMAX application. The proposed flower shaped MA, designed on a
9×9mm2 FR-4 substrate with 1 mm thickness, exhibits near unity normalized impedance at
5.5 GHz with an absorptivity of 98.7 %. A 4 element array of the MA is arranged in the form
of a line in the middle of the two radiating patches in order to suppress the propagation of
surface current between them at the operating frequency. Using the proposed flower shaped
MA, an isolation of nearly 35 dB is achieved. The MIMO structure is studied in terms of
return loss, isolation, overall gain, radiation pattern, Envelope Correlation Coefficient (ECC),
Diversity Gain (DG), and Total Active Reflection Co-efficient (TARC) etc. The structure is
finally fabricated and measured to show good agreement with the simulated results.
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Arepolage, Thiwanka. "Thermal fluxes control using Metamaterial and other techniques." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCD050.
Full textAbstract:
Cette thèse explore des méthodes avancées pour contrôler le flux thermique dans les métamatériaux thermiques et améliorer la performance des capteurs, tout en développant des solutions innovantes dans les circuits photoniques intégrés (PICs) et les applications associées. La recherche est divisée en deux principaux projets. Le premier projet développe des dispositifs pour concentrer la chaleur en utilisant des métamatériaux thermiques. Les conceptions existantes dans la littérature ne prenaient en compte que la conductivité thermique (K) sans considérer le produit densité-capacité thermique (ρC). L'analyse a montré que, bien que ces dispositifs fonctionnent bien en conditions stationnaires, ils présentent des limites dans les situations dépendant du temps. Pour y remédier, deux nouveaux concentrateurs thermiques ont été créés, prenant en compte à la fois K et ρC. Ces dispositifs ont été testés par simulation. L'un d'entre eux a été fabriqué par impression 3D métallique et testé expérimentalement. Les résultats ont confirmé que ces nouvelles conceptions contrôlent efficacement le flux thermique comme prévu. Le deuxième projet s'est concentré sur l'amélioration des performances des capteurs dans les PICs en gérant la chaleur. La première partie de ce projet a utilisé des tranchées et des radiateurs pour contrôler la chaleur issue de l'excitation plasmonique dans des nanodisques, réduisant les augmentations de température indésirables détectées par des nanofils. Ce projet a été testé expérimentalement. La deuxième partie a appliqué une méthode similaire aux détecteurs photothermiques à plasmons de surface (SPD) intégrés à des guides d'ondes en dioxyde de titane (TiO2). Des tranchées et des radiateurs ont été utilisés pour réduire les transferts de chaleur indésirables provenant de composants voisins, améliorant ainsi la précision des mesures. Les deux projets apportent de nouvelles solutions pour gérer la chaleur dans des systèmes à l'échelle nanométrique, montrant que la combinaison de simulations et de techniques de fabrication avancées permet de contrôler efficacement le comportement thermique dans des environnements complexes<br>This thesis explores advanced methods for controlling heat flow in thermal metamaterials and to enhance sensor performance and develop innovative solutions in photonic integrated circuits (PICs) and related applications. The research is divided into two main projects. The first project develops devices to concentrate heat using thermal metamaterials. Designs in the literature only considered thermal conductivity (K) and not the density-heat capacity product (ρC). The analysis showed that while the device worked well in steady-state conditions, it can lead to limitations in time-dependent situations. To address this, two new thermal concentrators were created, adressing both K and rho C. These devices were tested through simulation. One of them was fabricated by metal 3D printing and experimentally tested. The results confirmed that these new designs effectively controlled heat flow as expected. The second project focused on improving sensor performance in PICs by managing heat. The first part of this project used trenches and radiators to control heat from plasmonic excitation in nanodiscs, reducing unwanted temperature increases detected by nanowires. This project has been experimentally tested. The second part applied a similar method to photothermal surface plasmon detectors (SPDs) integrated with titanium dioxide (TiO2) waveguides. Trenches and radiators were used to reduce unwanted heat transfer from nearby components, improving measurement accuracy. Both projects provide new solutions for managing heat in nanoscale systems, showing that combining simulations with advanced fabrication techniques can lead to effective control of thermal behavior in complex environments
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Jiao, Jiao. "The simulation and structure design of optical metamaterials." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/the-simulation-and-structure-design-of-optical-metamaterials(b85aac76-61cf-4269-864a-5c0de60b715a).html.
Full textAbstract:
Metamaterials are artificial materials engineered to have properties that may not be found in nature. The most fundamental properties of metamaterials are the periodic and sub-wavelength pattern structure. Metamaterials that affect electromagnetic waves in optic wavelengths are called optical metamaterials. The goal of this Thesis was to lay the foundation for design and development of optical metamaterials as potential biomedical sensor. Current biomedical sensors can made of some sensitive biological element (e.g. microorganism and antibodies). The limitations of the biological elements can be due to their susceptibility to extraneous factors such as PH value and temperature. The metamaterials made of gold, aluminum, glass and quartz can bave very high biological stability. Understanding and design of metalmaterials to modulate electromagnetic properties was the focus of the PhD and this was enabled by the use of CST Microwave Studio® software.This PhD made a distinct contribution to the design of two Optical metamaterials. Circular Dichroism (CD) has been widely used to gain information about biomolecules, DNA and organic compounds but, due to problems with accuracy, some indistinct features cannot be detected. The first is Circular Dichroism (CD), which is based on the negative refractive index. The material architectures modeled consisted of a glass substrate and an aluminum nano-ring on top. The research methodology involved adjusting the dimensions of the ring and modelling the impact on CD spectrum. The research in this Thesis shows that controllable CD filter design using optical metamaterial techniques could make it possible to amplify the target signals or unlock jammed signals. The other optical metamaterial designed in this Thesis is a core-shell structure. As a unit cell, the single core-shell and core-shell chain can be built into a biomedical sensor. The aim of this type of sensor is to control the position and value of the Fano dip by regulating the structural parameters of the optical metamaterial. To accomplish this, a concentric spherical structure that consists of a silver core and a quartz (SiO2) shell was designed. The thickness of the shell and the diameter of the core was adjusted independently. The Fano signal was found in the extinction cross section and could be easily identified. This peculiarity allowed the single or multiple optical scales to be marked in the visible spectrum. This can improve efficiency and precision when compared with traditional methods for the detection of biological macromolecules. This work opens new opportunities for fano resonance engineering in plasmonic metamaterials and nanostructures.
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Beattie, Ewan. "Influence of patterns in paper-based strips onmechanical properties." Thesis, KTH, Maskinkonstruktion (Inst.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235977.
Full textAbstract:
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.<br>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.
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Martínek, Luděk. "Antény s kryty z metamateriálů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-219978.
Full textAbstract:
This thesis deals with microstrip antennas covered by the metamaterials. First, are described planar antennas, their problems and the emergence of surface waves. Surface waves can cause unwanted coupling among particular parts of the structure and can degrade its parameters. The problem can be solved using an electromagnetic band gap structure (EBG). These periodic structures are able to suppress surface waves in different frequency bands. It is shown how the EBG structure in the function superstate improve directivity and antenna gain. Radiation conventional microstrip antenna with metallo-dielectric EBG superstrate and with the purely dielectric double-layer superstrate is described. The both structures are designed and simulated in CST Microwave Studio program. Further is described the antenna radiation with so-called mushroom structure and metallo-dielectric EBG superstate. The structure is again designed and simulated in CST MWS program. Finally, there are two structures with metallo-dielectric superstate implemented and measured.