Este trabalho visou ao desenvolvimento de antenas de ressoador dielétrico de banda dupla em frequências de micro-ondas por meio do estabelecimento de uma metodologia de projeto para as mesmas e da proposição de configurações inéditas de antenas desse tipo. Estudos realizados sobre antenas de ressoador dielétrico e sobre suas técnicas de projeto forneceram a base para a elaboração de um procedimento de projeto para antenas de banda dupla que explora a flexibilidade das antenas de ressoador dielétrico. Empregando-se esse procedimento de projeto, duas antenas com configurações originais foram desenvolvidas para operar em frequências de micro-ondas. Uma delas é uma antena de ressoador dielétrico cilíndrica sobre plano de terra, destinada a operar nas frequências centrais de 3,94 GHz e de 5,42 GHz, com diagrama de radiação direcional e polarização circular na primeira banda de operação e com diagrama de radiação omnidirecional e polarização linear na segunda. A outra antena consiste em uma antena de ressoador dielétrico cilíndrica sobre substrato dielétrico aterrado, cujas frequências centrais de operação são 3,99 GHz e 6,20 GHz, com diagrama de radiação direcional e polarização circular em ambas as bandas de operação. O projeto das duas antenas também levou a contribuições novas adicionais em alguns temas específicos relacionados: estruturas de excitação para antenas de ressoador dielétrico, circuitos acopladores híbridos de 90° de banda dupla, circuitos de alimentação para antenas de banda dupla e modelos matemáticos para o ressoador dielétrico cilíndrico isolado no espaço livre. Os comportamentos previstos teoricamente para as antenas projetadas são confirmados por meio de resultados obtidos por simulação eletromagnética e por medição experimental, o que indica a validade das hipóteses adotadas, das configurações de antena propostas e da metodologia de projeto concebida, demonstrando também a flexibilidade desta para variadas especificações de antena. Os avanços obtidos com este trabalho e as melhorias que podem ser efetuadas sobre o mesmo são identificados examinando-se resultados recentemente publicados na literatura técnica. Este trabalho foi realizado na forma de uma pesquisa de doutorado sanduíche, desenvolvida parcialmente na University of Houston sob a supervisão do Prof. Stuart A. Long. / This work aimed at the development of microwave dual-band dielectric resonator antennas by means of establishing a design methodology for them and of proposing novel configurations of this antenna type. Studies on dielectric resonator antennas and on their design techniques provided the ground for elaborating a design procedure for dual-band antennas that exploits the flexibility of dielectric resonator antennas. By employing this design procedure, two antennas with original configurations have been developed for operation at microwave frequencies. One of them is a cylindrical dielectric resonator antenna on a ground plane, intended for operation at the center frequencies of 3.94 GHz and 5.42 GHz, with a directional radiation pattern and circular polarization in the first operating band and with an omnidirectional radiation pattern and linear polarization in the second one. The other antenna consists of a cylindrical dielectric resonator antenna on a grounded dielectric substrate, whose operating center frequencies are 3.99 GHz and 6.20 GHz, with a directional radiation pattern and circular polarization in both operating bands. The design of the two antennas also led to additional new contributions in some related specific subjects: excitation structures for dielectric resonator antennas, dual-band 90°-hybrid couplers, feeding circuits for dual-band antennas, and mathematical models for the cylindrical dielectric resonator isolated in free space. The behaviors theoretically expected for the designed antennas are confirmed by means of results obtained from electromagnetic simulation and from experimental measurements, which indicates the validity of the assumed hypotheses, of the proposed antenna configurations and of the conceived design methodology, also demonstrating the flexibility of the latter for various antenna specifications. The advances obtained with this work and the improvements that can be made on it are identified by examining results recently published in the technical literature. This work was carried out as a sandwich doctoral research, developed at the University of Houston under the supervision of Prof. Stuart A. Long.

A new class of micromachined devices called thin-film piezoelectric-on-substrate (TPoS) resonators is introduced, and the performance of these devices in RF and sensor applications is studied. TPoS resonators benefit from high electromechanical coupling of piezoelectric transduction mechanism and superior acoustic properties of a substrate such as single crystal silicon. Therefore, the motional impedance of these resonators are significantly smaller compared to typical capacitively-transduced counterparts while they exhibit relatively high quality factor and power handling and can be operated in air. The combination of all these features suggests TPoS resonators as a viable alternative for current acoustic devices. In this thesis, design and fabrication methods to realize dispersed-frequency lateral-extensional TPoS resonators are discussed. TPoS devices are fabricated on both silicon-on-insulator and thin-film nanocrystalline diamond substrates. The performance of these resonators in simple and low-power oscillators is measured and compared. Furthermore, a unique coupling technique for implementation of high frequency filters is introduced in which dual resonance modes of a single resonant structure are coupled. The measured results of this work show that these filters are suitable candidates for single-chip implementation of multiple-frequency narrow-band filters with high out-of-band rejection in a small footprint.

This thesis deals with the investigations on the atomic composition, chemical surface states and microstructural features of barium titanate and other electronic ceramics namely barium polytitantes, calcium manganites and magnesium calcium titanate by surface analytical techniques. After presenting a brief introduction on the ceramic materials studied in terms of their crystal structures, electrical properties, nonstoichiometry and interfacial characteristics, the thesis describes the synthesis of the ceramics and the methodology of the different surface analytical techniques utilized such as backscattering spectrometry (BS), an ion beam analysis (IBA) technique, X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS). The XPS investigations on the chemical surface states of polycrystalline barium titanate having well-defined electrical characteristics reveal the prevalence of Ba in two distinct chemical environments : the one corresponding to the lower binding energy is related to the dielectric while the other having higher binding energy is correlated to semiconducting properties of the ceramics. Processes such as abrasion or polishing make the surfaces more reactive and susceptible to atmospheric contamination. Sputter cleaning causes surface modification leading to changes in the Ba (3d) and Ti (2p) spectra. Studies on the surface atomic composition by BS and microstructural features of doped barium titanate ceramics reveal their interfacial characteristics in terms segregation of dopants or metal ion constituents. Surfaces of these ceramics exhibit cationic as well as anionic nonstoichiometry depending on the processing steps involved. Ceramics synthesized by oxalate precursor route are Ti-rich while those prepared by gel-to-crystallite method are Ba-rich. These are correlated to the chemical processes and background impurities which in turn control the microstructures. Barium titanate substitued with > 1 at. % Mn are deficient in oxygen and exist as the hexagonal polymorph. Acceptors segregate at the grain boundaries accompanied by the enrichment of Ti leading to PTCR or GBLC characteristics. The oxygen nonstoichiometry prevailing in the surface regions of differently processed calcium manganites is investigated by way of depth profile measurements involving 16O(a,a) 16O resonant scattering. These studies reveal extensive compositional heterogeneity across the surface layers particularly in the manganite specimens annealed in lower po2 leading to the stabilization of brownmillerite phase. Two of the microwave dielectric ceramics namely dibarium nona-titanate and barium tetra-titanate with suitable variations in Ba:Ti ratios have been synthesized by the carbonate-gel precipitation. The corresponding dense ceramics have high permittivity (~ 52) and low temperature coefficient of permittivity (TCK ~ 5 ppm /0C). Extensive miscibility between the ilmenite-type MgTiO3 and perovskite-type CaTiO3 over a wide compositional range is brought about by the simultaneous equivalent substitution of Al3+ + La3+. The resulting (Mg1-(x+y)CaxLay)(Ti1-yAly)O3 ceramics exhibit improved microwave dielectric properties by way of high permittivity, low TCK and high quality factor. The microarea elemental distribution and chemical surface state studies reveal the complexity in the Mg/Ca distribution and its correlation with the solid state miscibility as well as dielectric properties. The discontinuous changes in the local site symmetry of the cationic substituents in these ceramics have been investigated by the photoluminescence spectra using Pr3+ as the emission probe.

nÃo hà / à crescente o interesse mundial pelo desenvolvimento de tecnologias chamadas âverdesâ que possibilitem o uso de produtos com menor impacto ao meio ambiente, assim como tambÃm se fortalecem as polÃticas de incentivo ao aproveitamento mÃximo e sustentÃvel dos recursos naturais. O principal objetivo desse estudo foi desenvolver nanobiocompÃsitos superparamagnÃticos para aplicaÃÃo como antenas ressoadoras dielÃtricas. Para tal, um plÃstico termorrÃgido biobaseado foi preparado utilizando o cardanol em alternativa aos fenÃis petroquÃmicos. Esse plÃstico termorrÃgido foi utilizado como matriz para o preparo de biocompÃsitos, utilizando 15% em massa de fibra de bucha bruta e tambÃm modificada por tratamento quÃmico (NaOH 5, 10 e 15% e NaClO 1%) como fase dispersa. Para o preparo dos nanobiocompÃsitos, alÃm da fibra de bucha, nanopartÃculas de magnetita, sintetizadas pelo mÃtodo da coprecipitaÃÃo, foram impregnadas no plÃstico termorrÃgido em diferentes teores de 1, 5 e 10% em massa. TÃcnicas de Termogravimetria (TG), Calorimetria exploratÃria diferencial (DSC), AnÃlise dinÃmico-mecÃnica (DMA), Microscopia eletrÃnica de varredura (MEV), Microscopia Ãptica, Microscopia eletrÃnica de transmissÃo (MET), DifraÃÃo de raios X (DRX), Espectroscopia no infravermelho com transformada de Fourier (FTIR), Espectroscopia MÃssbauer, Ensaios de resistÃncia à traÃÃo, Medidas dielÃtricas, Magnetometria de amostra vibrante (VSM) e BiodegradaÃÃo em solo simulado foram utilizadas para caracterizaÃÃo. Os resultados mostraram que o tratamento alcalino melhorou a estabilidade tÃrmica e o Ãndice de cristalinidade da fibra de bucha. O agente reticulador utilizado (DETA) mostrou-se eficiente, possibilitando a cura completa dos materiais. Os biocompÃsitos com fibra tratada apresentaram maior estabilidade tÃrmica, resistÃncia à traÃÃo superior e melhor Ãndice de biodegradaÃÃo em relaÃÃo ao biocompÃsito com fibra natural. A magnetita sintetizada exibiu tamanho nanomÃtrico, alÃm de alta pureza, alta cristalinidade e carÃter superparamagnÃtico. Todos os nanobiocompÃsitos exibiram superparamagnetismo e mostraram excelente estabilidade tÃrmica, boas taxas de biodegradaÃÃo e melhor resistÃncia mecÃnica para o material com 10% de magnetita. Todas as antenas ressoadoras dielÃtricas preparadas apresentaram perda de retorno satisfatÃria e, portanto, adequaÃÃo para fins comerciais e tecnolÃgicos, com maior potencial para atuaÃÃo em banda larga. / There is a growing global interest for the development of green technologies that allow the use of products with less damage to environment, as well as for maximum and sustainable use of natural resources. The main aim of this study was to develop superparamagnetic nanobiocomposites for application as dielectric resonator antennas. For this purpose, a biobased thermoset plastic was prepared by using cardanol as an alternative to petrochemical phenol. This thermoset plastic was used as a polymer matrix and biocomposites were prepared by using 15 wt% of untreated and modified sponge gourd fibers by chemical treatment (NaOH 5, 10, and 15 wt% and NaClO 1 wt%) as dispersed phase. For the nanobiocomposites preparation, besides the sponge gourd fibers insertion, the thermoset plastic were also impregnated with magnetite nanoparticles in different contents (1, 5, and 10 wt%). Techniques of Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), Scanning Electron Microscopy (SEM), Optical Microscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), MÃssbauer Spectroscopy, Tensile testing, Dielectric measurements, Vibrating Sample Magnetometry (VSM) and Biodegradation in simulated soil were performed for characterization. The results showed that alkaline treatment improved the thermal stability and the crystallinity index of the sponge gourd fiber. The crosslinking agent used (Diethylenetriamine) was efficient and enabled complete cure for all materials. The biocomposites reinforced by treated fiber showed better thermal stability, superior performance in Tensile testing and greater biodegradation rates, when compared to the biocomposite reinforced by raw fiber. The magnetite particles exhibited nanometric size, high purity and crystallinity, and superparamagnetic character. All nanobiocomposites showed superparamagnetic behavior, excellent thermal stability, good biodegradation rates, and better mechanical strength for the material with magnetite 10 wt%. All dielectric resonators antennas exhibited satisfactory return loss and suitability for commercial and technological applications, especially for performance in broadband.

SILVA, André Leandro. Nanobiocompósitos superparamagnéticos para aplicação como antenas ressoadoras dielétricas. 2014. 126 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Departamento de Quimica Orgânica e Inorgânica, Programa de Pós-Graduação e Biotecnologia, Renorbio - Rede Nordeste de Biotecnologia, Fortaleza-CE, 2014. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-05-20T13:09:52Z No. of bitstreams: 1 2014_tese_alsilva.pdf: 6480806 bytes, checksum: 946e32810e24c5137dfbba52bfd30bb8 (MD5) / Approved for entry into archive by demia Maia (demiamlm@gmail.com) on 2016-05-20T13:10:43Z (GMT) No. of bitstreams: 1 2014_tese_alsilva.pdf: 6480806 bytes, checksum: 946e32810e24c5137dfbba52bfd30bb8 (MD5) / Made available in DSpace on 2016-05-20T13:10:43Z (GMT). No. of bitstreams: 1 2014_tese_alsilva.pdf: 6480806 bytes, checksum: 946e32810e24c5137dfbba52bfd30bb8 (MD5) Previous issue date: 2014 / There is a growing global interest for the development of green technologies that allow the use of products with less damage to environment, as well as for maximum and sustainable use of natural resources. The main aim of this study was to develop superparamagnetic nanobiocomposites for application as dielectric resonator antennas. For this purpose, a biobased thermoset plastic was prepared by using cardanol as an alternative to petrochemical phenol. This thermoset plastic was used as a polymer matrix and biocomposites were prepared by using 15 wt% of untreated and modified sponge gourd fibers by chemical treatment (NaOH 5, 10, and 15 wt% and NaClO 1 wt%) as dispersed phase. For the nanobiocomposites preparation, besides the sponge gourd fibers insertion, the thermoset plastic were also impregnated with magnetite nanoparticles in different contents (1, 5, and 10 wt%). Techniques of Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), Scanning Electron Microscopy (SEM), Optical Microscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Mössbauer Spectroscopy, Tensile testing, Dielectric measurements, Vibrating Sample Magnetometry (VSM) and Biodegradation in simulated soil were performed for characterization. The results showed that alkaline treatment improved the thermal stability and the crystallinity index of the sponge gourd fiber. The crosslinking agent used (Diethylenetriamine) was efficient and enabled complete cure for all materials. The biocomposites reinforced by treated fiber showed better thermal stability, superior performance in Tensile testing and greater biodegradation rates, when compared to the biocomposite reinforced by raw fiber. The magnetite particles exhibited nanometric size, high purity and crystallinity, and superparamagnetic character. All nanobiocomposites showed superparamagnetic behavior, excellent thermal stability, good biodegradation rates, and better mechanical strength for the material with magnetite 10 wt%. All dielectric resonators antennas exhibited satisfactory return loss and suitability for commercial and technological applications, especially for performance in broadband. / É crescente o interesse mundial pelo desenvolvimento de tecnologias chamadas “verdes” que possibilitem o uso de produtos com menor impacto ao meio ambiente, assim como também se fortalecem as políticas de incentivo ao aproveitamento máximo e sustentável dos recursos naturais. O principal objetivo desse estudo foi desenvolver nanobiocompósitos superparamagnéticos para aplicação como antenas ressoadoras dielétricas. Para tal, um plástico termorrígido biobaseado foi preparado utilizando o cardanol em alternativa aos fenóis petroquímicos. Esse plástico termorrígido foi utilizado como matriz para o preparo de biocompósitos, utilizando 15% em massa de fibra de bucha bruta e também modificada por tratamento químico (NaOH 5, 10 e 15% e NaClO 1%) como fase dispersa. Para o preparo dos nanobiocompósitos, além da fibra de bucha, nanopartículas de magnetita, sintetizadas pelo método da coprecipitação, foram impregnadas no plástico termorrígido em diferentes teores de 1, 5 e 10% em massa. Técnicas de Termogravimetria (TG), Calorimetria exploratória diferencial (DSC), Análise dinâmico-mecânica (DMA), Microscopia eletrônica de varredura (MEV), Microscopia óptica, Microscopia eletrônica de transmissão (MET), Difração de raios X (DRX), Espectroscopia no infravermelho com transformada de Fourier (FTIR), Espectroscopia Mössbauer, Ensaios de resistência à tração, Medidas dielétricas, Magnetometria de amostra vibrante (VSM) e Biodegradação em solo simulado foram utilizadas para caracterização. Os resultados mostraram que o tratamento alcalino melhorou a estabilidade térmica e o índice de cristalinidade da fibra de bucha. O agente reticulador utilizado (DETA) mostrou-se eficiente, possibilitando a cura completa dos materiais. Os biocompósitos com fibra tratada apresentaram maior estabilidade térmica, resistência à tração superior e melhor índice de biodegradação em relação ao biocompósito com fibra natural. A magnetita sintetizada exibiu tamanho nanométrico, além de alta pureza, alta cristalinidade e caráter superparamagnético. Todos os nanobiocompósitos exibiram superparamagnetismo e mostraram excelente estabilidade térmica, boas taxas de biodegradação e melhor resistência mecânica para o material com 10% de magnetita. Todas as antenas ressoadoras dielétricas preparadas apresentaram perda de retorno satisfatória e, portanto, adequação para fins comerciais e tecnológicos, com maior potencial para atuação em banda larga.

Le transport des ondes joue un rôle majeur dans les systèmes de communication comme le Wifi ou les fibres optiques. Les principaux problèmes rencontrés dans ces systèmes concernent la protection contre les intrusions, la consommation d’énergie et le filtrage modal. Nous proposons différentes expériences micro-ondes mettant toutes en œuvre une mise en forme des ondes, pour traiter ces problèmes. Dans une cavité micro-ondes, des états de diffusion particuliers sont générés en s’appuyant uniquement sur des mesures de transmission et sur le formalisme du temps de retard de Wigner-Smith. Ces états sont capables d’éviter une région déterminée de la cavité, de se concentrer sur un point particulier, ou de suivre une trajectoire d’une particule classique. Le filtrage de mode est mis en œuvre dans un guide d’ondes aux frontières ondulées et en présence de pertes dépendant de la position. Le profil du guide est choisi de façon à ce que les deux modes de Bloch qui se propagent encerclent un point exceptionnel. Cette trajectoire s’accompagne d’une transition non-adiabatique entre les deux modes et d'un filtrage asymétrique de ces modes. La thèse présente également des travaux liés à la problématique des algorithmes de « recherche quantique », notamment l’algorithme de Grover. Cette recherche est mise en œuvre dans un réseau en nid d’abeilles de résonateurs micro-ondes couplés, bien décrits par un modèle de liaisons fortes (le système constitue un analogue micro-ondes du graphène). Une expérience de preuve de principe propose la recherche de deux résonateurs distincts reliés au réseau. La loi d’échelle attendue pour cet algorithme est expérimentalement obtenue dans une chaîne linéaire / Transport of waves plays an important role in modern communication systems like Wi-Fi or optical fibres. Typical problems in such systems concern security against possible intruders, energy consumption, time efficiency and the possibility of mode filtering. Microwave experiments are suited to study this kind of problems, because they offer a good control of the experimental parameters. Thus we can implement the method of wave shaping to investigate atypical transport phenomena, which address the mentioned problems. Wave front shaping solely based on the transmission together with the Wigner-Smith time delay formalism allows me to establish special scattering states in situ. These scattering states avoid a pre-selected region, focus on a specific spot or follow trajectories of classical particles, so called particle-like scattering states. Mode filtering is induced inside a waveguide with wavy boundaries and position dependent loss. The boundary profiles are chosen in such a way that the two propagating modes describe an encircling of an exceptional point in the Bloch picture. The asymmetric mode filtering is found due to the appearing non-adiabatic transitions. Another part of my work deals with Grover’s quantum search. I put such a search into practice in a two-dimensional graphene-lattice using coupled resonators, which form a tight-binding analogue. In this proof of principle experiment we search for different resonators attached to the graphene-lattice. Furthermore, the scaling behaviour of the quantum search is quantified for a linear chain of resonators