Spelling suggestions: "subject:"dielectric resonator""
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Estudo dos efeitos da adiÃÃo de TiO2 E V2O5 nas propriedades dielÃtricas da matriz cerÃmica Na2Nb4O11 (NN00) e suas aplicaÃÃes em ressoadores dielÃtricos / Study of the effect of the addition of TiO2 AND V2O5 in the dielectric properties of ceramic matrix NA2NB4O11 (NN00) and its applications in dielectric resonators.Mairton Cavalcante Romeu 12 February 2014 (has links)
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Neste trabalho, foram investigadas as propriedades estruturais e dielÃtricas da fase monoclÃnica da cerÃmica ferroelÃtrica Na2Nb4O11 com adiÃÃo de diÃxido de titÃnio (TiO2) e PentÃxido de vanÃdio (V2O5) nas proporÃÃes de 2, 5 e 10% em massa. Os pÃs Na2Nb4O11 foram produzidos pelo mÃtodo convencional de reaÃÃo em estado sÃlido. ApÃs a calcinaÃÃo, as amostras foram prensadas na forma de pastilhas cilÃndricas e, em seguida, sinterizadas. O estudo da estrutura e da composiÃÃo das amostras foi feito atravÃs de difraÃÃo de raios-X e Refinamento Rieteveld e um estudo da morfologia foi realizado atravÃs de Microscopia EletrÃnica de Varredura. As medidas de densidade foram obtidas atravÃs da picnometria. A caracterizaÃÃo dielÃtrica foi realizada na faixa de radiofrequÃncias e de micro-ondas. Em ambos os casos, foram realizados um estudo das propriedades em relaÃÃo à variaÃÃo da temperatura para possÃvel aplicaÃÃo em dispositivos que atuam em RadiofrequÃncia e Microondas. O objetivo principal desse trabalho foi obter ressoadores dielÃtricos cerÃmicos com permissividade dielÃtrica alta, baixas perdas dielÃtricas e estabilidade tÃrmica, pois essas propriedades sÃo necessÃrias para as aplicaÃÃes em filtros e antenas dielÃtricas. Nas medidas realizadas em temperatura ambiente de 25ÂC obtivemos um alto valor da permissividade dielÃtrica (εâr = 129.29 ) com o NN2V ( 2% de V2O5) e um valor da tangente de perda, relativamente baixo ( tanδ = 3.25x10-2 ) em 1 MHz. Na temperatura de 400ÂC e numa frequÃncia fixa de 1 MHz, foi obtido um alto valor da permissividade dielÃtrica com εâr= 358.23 e um valor de perda dielÃtrica em torno de 3,49 x10-1 para amostra NN2Ti. A medida do coeficiente de temperatura da frequÃncia de ressonÃncia (τf) mostrou a possibilidade de atingir a estabilidade tÃrmica (τf = 0) com o aumento do nÃvel de adiÃÃo de V2O5. Para a amostra NN00, obtivemos um τf= -3378,42 ppm/ÂC. Com a adiÃÃo do V2O5, este valor vai se aproximando do zero e atinge τf = -1348,618ppm/ÂC para o NN10V. As medidas na faixa de micro-ondas foram obtidas utilizando-se o mÃtodo Hakki-Coleman. Uma simulaÃÃo numÃrica foi realizada com cada amostra, verificando-se a reciprocidade com os dados experimentais. Neste estudo obtivemos uma cerÃmica NN10V, Ãtil para a aplicaÃÃo em dispositivos de antenas omnidirecionais de baixo ganho.
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Dielectric resonator in the presence of a lossy conductorJohnston, Scott B. 30 June 2009 (has links)
This thesis develops a method for obtaining the complex resonant frequency of a post dielectric resonator in the presence of a lossy conductor. A full field analysis is performed on an infinite dielectric rod from which the complex propagation constant and modal solutions are found. Using a single dominant mode (HEM<sub>ll</sub>), the boundary conditions at the end of the resonator are enforced, to obtain a complex reflection coefficient. Using the propagation constant from the infinite dielectric rod and the reflection coefficient derived from considering the dielectric-air interface at the resonator ends, a two dimensional search is performed to find the complex frequency for which the gain/phase criterion of the resonator is satisfied. In the final step, boundary conditions are enforced for a lossy conductor at a distance Az from the dielectric which yields the objective -- the complex resonate frequency of a post dielectric in close proximity of a lossy conductor / Master of Science
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Design and Prototyping of an Antenna-Coupled CryotronJensen, Shauna 16 May 2014 (has links)
Grid-scale integration of renewable energy sources and smart grid devices has created new demands in flexible power conversion. State-of-the-art semiconductor power switches present limitations in power handling capability, as well as forward and reverse breakdown voltages. Superconducting materials are a viable alternative due to their robustness against high ampacities, large electric fields and abrupt changes in power flow. This work pays focus to material testing and apparatus design for an antenna-coupled cryotron (ACC), which is a superconducting power switch.Design, fabrication and testing are examined for a longitudinal resonant cavity, paired with monopole transmit and modified slot receive antennae. These couple radio frequency (RF) energy into superconducting thin film niobium (Nb) carrying high current densities (∼105A/cm2), thereby creating an antenna-coupled cryotron.Induced electromagnetic field effects at the receive antenna alter superconductive fluid dynamics. The theorized quality in manipulating this mechanism is a rapid normal-conductivity transition (µs), which affects a switch "off" state. Functional evaluation of the device as a waveguide revealed evanescent mode resonance at frequencies below the waveguide cut-off of ∼18GHz. The thin film Nb was deposited on a quartz dielectric, which penetrated the waveguide and supported evanescent resonances within the structure.Altered resistivity and critical transition-point properties emerged from device testing at applied RF. When the Nb film temperature-dependent coherence length was comparable to its thickness, perpendicular magnetic field application generated an Abrikosov vortex state, energetically favoring a mixed domain condensate. Interaction of the magnetically-induced flux vortex lattice with Lorentz current forces gave rise to resistive changes within the metal. Three resistive transition mechanisms developed: a latch to normal state resistance, attributed to cooper-pair destruction avalanche induced near critical transition points; a small reversible increase in resistance (∼mV), arising from flux-flow within an intermediate state at peak resonance; as well as temporal alterations in superfluid dynamics from disequilibrium in the quasi-particle population. The RF induced superfluid effects were observable in separate terms of electric and thermodynamic fluctuations.Motivation for this work is the eventual design of a high voltage, high current and low cost power switch, able to function where existing semiconductor technology fails. Concentration is paid to the fundamental theory, physics and methodology in conceptual testing and design of prototype ACCs. Assessment focuses on preliminary findings and concludes with next stage design requirements.
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Silicon carbide RF-MEM resonatorsDusatko, Tomas A. January 2006 (has links)
No description available.
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Silicon carbide RF-MEM resonatorsDusatko, Tomas A. January 2006 (has links)
A low-temperature (<300°C) method to fabricate electrostatically actuated microelectromechanical (MEM) clamped-clamped beam resonators has been developed. It utilizes an amorphous silicon carbide (SiC) structural layer and a thin polyimide spacer. The resonator beam is constructed by DC sputtering a tri-layer composite of low-stress SiC and aluminum over the thin polyimide sacrificial layer, and is then released using a microwave O 2 plasma etch. Deposition parameters have been optimized to yield low-stress films (<50MPa), in order to minimize the chance of stress-induced buckling or fracture in both the SiC and aluminum. Characterization of the deposited SiC was performed using several different techniques including scanning electron microscopy, EDX and XRD. / Several different clamped-clamped beam resonator designs were successfully fabricated and tested using a custom built vacuum system, with measured frequencies ranging from 5MHz to 25MHz. A novel thermal tuning method is also demonstrated, using integrated heaters directly on the resonant structure to exploit the temperature dependence of the Young's modulus and thermally induced stresses.
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Modeling and design of resonators for electron paramagnetic resonance imaging and ultra high field magnetic resonance imagingStefan, Anca Irina, January 2005 (has links)
Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Includes bibliographical references (p. 115-120).
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Fabry-Perot and Whispering Gallery Modes In Realistic Resonator ModelsFoster, David H. 03 1900 (has links)
xviii, 213 p. / A print copy of this title is available through the UO Libraries under the call number: SCIENCE QC476.5 .F67 2006 / We investigate models describing two classes of microresonators: those having the
shape of a dome, and those having an oval (deformed circle or sphere) shape. We
examine the effects of dielectric interfaces in these structures. For the dome cavity, we derive efficient numerical methods for finding exact electromagnetic
resonances. In the dome consisting of a concave conductor and a planar,
dielectric Bragg mirror, we discover a phenomenon which we call paraxial mode mixing
(PMM) or classical spin-orbit coupling. PMM is the sensitive selection of the true
electromagnetic modes. The true modes are generally mixtures of pairs of vectorial
Laguerre-Gauss modes. While each member of an LG pair possesses definite orbital
angular momentum and spin (polarization), the mixed modes do not, and exhibit rich, non-uniform polarization patterns. The mixing is governed by an orthogonal transformation
specified by the mixing angle (MA). The differences in reflection phases of a Bragg mirror at electric s and p polarization can be characterized in the paraxial
regime by a wavelength-dependent quantity εs - εp. The MA is primarily determined
by this quantity and varies with an apparent arctangent dependence, concomitant
with an anticrossing of the maximally mixed modes. The MA is zero order in quantities
that are small in the paraxial limit, suggesting an effective two-state degenerate
perturbation theory. No known effective Hamiltonian and/or electromagnetic perturbation
theory exists for this singular, vectorial, mixed boundary problem. We develop
a preliminary formulation which partially reproduces the quantitative mixing behavior.
Observation of PMM will require both small cavities and highly reflective mirrors.
Uses include optical tweezers and classical and quantum information. For oval dielectric resonators, we develop reduced models for describing whispering
gallery modes by utilizing sequential tunneling, the Goos-H¨anchen (GH) effect, and
the generalized Born-Oppenheimer (adiabatic) approximation (BOA). While the GH
effect is found to be incompatible with sequential tunneling, the BOA method is found
to be a useful connection between ray optics and the exact wave solution. The GH effect is also shown to nicely explain a new class of stable V-shaped dome
cavity modes. / Adviser: Dr. Jens Noeckel.
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Structural and dielectric properties of V2O5 addition on Bi5Ti3FeO15 ceramic matrix / Estudo das propriedades dielÃtricas e estruturais do Bi5Ti3FeO15 adicionado de V2O5Francisco Andrà Andrade de Aguiar 08 January 2016 (has links)
O Bi5Ti3FeO15 foi sintetizado pelo mÃtodo de ReaÃÃo no Estado SÃlido (RES) e posteriormente adicionado de V2O5 (PentÃxido de VanÃdio) objetivando melhorar suas propriedades dielÃtricas. Para as anÃlises estruturais foram utilizadas as seguintes tÃcnicas: DifraÃÃo de Raios-X (DRX), Microscopia EletrÃnica de Varredura (MEV), Espectroscopia de DispersÃo de Energia de Raios-X (EDS), Espectroscopia Raman e Infravermelho (IV). Para o estudo das propriedades dielÃtricas do material em radiofrequÃncia e em microondas, foram empregadas, respectivamente, a Espectroscopia de ImpedÃncia (EI) e o mÃtodo de Hakki e Coleman. A tÃcnica de DRX foi utilizada para identificar a fase BFT pura, bem como as duas novas fases originadas a partir da adiÃÃo de V2O5: Bi4V1.5Fe0.5O10.5 e Bi2Ti2O7. As alteraÃÃes na morfologia dos grÃos e a resposta dielÃtrica foram atribuÃdas à presenÃa destas fases secundÃrias. Em radiofrequÃncia verificou-se que a adiÃÃo de V2O5 aumentou a permissividade dielÃtrica e reduziu os valores de tangente de perda, resultados semelhantes aos obtidos em microondas. Ressonadores DielÃtricos foram fabricados como um protÃtipo para antena monopolo. Os valores de frequÃncia de funcionamento da antena variaram entre 2,4 GHz e 3,1 GHz. Jà os valores de coeficiente de temperatura da frequÃncia ressonante (f) variaram de -330 a -192 ppm/ÂC. Assim sendo, a cerÃmica BFT adicionada de V2O5, pode ser utilizada em dispositivos de microondas, como telefones mÃveis, por exemplo. / The Bi5Ti3FeO15 (BFT) was synthesized by the solid state reaction method (SLR) and then added by V2O5 (vanadium pentoxide) to improve its dielectric properties. For the structural analyses the following technics were used: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman and infrared spectroscopy. For the dielectric propeties of the material at radiofrequency and microwave ranges, impedance spectroscopy (IS) and the Hakki-Coleman methods were used respectively. The XRD technique was used to identify the BFT phase as well as the two new ones (Bi4V1.5Fe0.5O10.5 and Bi2Ti2O7). Changes in the grain morphology and the dielectric response were assigned due to the presence of these secondary phases. The V2O5 addition increased the dielectric permittivity and reduced the loss tangent values at radiofrequency range; similar results were obtained at microwave. The Dielectric resonators (DR) were fabricated as a prototype for monopole antenna. The antenna operating frequency (2.4 - 3.1 GHz) and temperature coefficient of resonance frequency (τf) (from -330 to -192 ppm/ÂC) changed as a function of V2O5 concentration in the DR. Thus, BFT ceramics added by V2O5 are good candidates to be used for microwave devices as cell mobile phones, for example.
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Design Procedures for Series and Parallel Feedback Microwave DROsAlaslami, Nauwaf 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / Clear procedures for designing dielectric resonator oscillators (DROs) are presented in
this thesis, including built examples to validate these design procedures. Both series
and parallel feedback DROs are discussed and the procedures for building them are
presented. Two examples at different frequencies for each type of DRO are constructed
and tested with the results shown. The first is at a frequency of approximately 6.22
GHz and the second for the higher frequency of 11.2 GHz. The DROs for the desired
frequencies are designed using the Microwave Office (MWO) software by AWR with
the design based on the small-signal model (scattering parameters). Oscillators are
produced using the negative resistance method. The circuit achieves low noise by using
a dielectric resonator with a high Q factor. Both the series and parallel feedback DRO
circuits can be mechanically tuned around the resonant frequency to maximize
performance.
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Antenas de ressoador dielétrico de banda dupla em frequências de micro-ondas. / Microwave dual-band dielectric resonator antennas.Seko, Murilo Hiroaki 17 April 2018 (has links)
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.
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