Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2018-06-11T17:51:51Z No. of bitstreams: 1 AlexandreMA_DISSERT.pdf: 21200920 bytes, checksum: 988dc3f3c5290a8f67225c05b46914a0 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2018-06-18T16:52:15Z (GMT) No. of bitstreams: 1 AlexandreMA_DISSERT.pdf: 21200920 bytes, checksum: 988dc3f3c5290a8f67225c05b46914a0 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2018-06-18T16:53:10Z (GMT) No. of bitstreams: 1 AlexandreMA_DISSERT.pdf: 21200920 bytes, checksum: 988dc3f3c5290a8f67225c05b46914a0 (MD5) / Made available in DSpace on 2018-06-18T16:53:22Z (GMT). No. of bitstreams: 1 AlexandreMA_DISSERT.pdf: 21200920 bytes, checksum: 988dc3f3c5290a8f67225c05b46914a0 (MD5) Previous issue date: 2018-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Demand in wireless networks has increased considerably in recent years. Consequently, the study of system components has also increased. Within this context, antennas are fundamental elements in the physical layer in radiofrequency communications, and their study has become a research area with great advances. The need in certain systems for smaller antennas and more adaptability in the space makes the microstrip antennas in potential substitutes of the traditional antennas. This work aims to find prototypes of microfite antennas that have physical and electrical characteristics, such as gain and polarization, superior to the commercial antennas of a FPV communication system (First Person View) operating at 5.8 GHz. The methodology used in this research consists of a theoretical survey about circular polarization antennas, design, simulate and construct these antennas using different substrates in order to verify their performance and to ship them in an FPV system. The results obtained through the simulation are compared with the experimental results in order to attest to the model in question based on the literature used in this work. Preliminarily, the simulated and measured results show that the Triangular Patch Antennas have all the desirable characteristics for operation in the FPV system, being possible to board them for the obtaining of images and analysis of the performance of the system / A demanda em redes de comunicação sem fio tem aumentado consideravelmente nos últimos anos. Consequentemente, o estudo dos componentes dos sistemas também aumentou. Dentro desse contexto, as antenas são elementos fundamentais na camada física em comunicações via radiofrequência, e o seu estudo tornou-se uma área de pesquisa com grandes avanços. A necessidade em determinados sistemas por antenas de menor porte e mais adaptabilidade no espaço tornam as antenas de microfita em potenciais substitutos das antenas tradicionais. Diante disso, esse trabalho objetiva encontrar protótipos de antenas de microfita que possuam características físicas e elétricas, como ganho e polarização, superiores às antenas comerciais de um sistema de comunicação em FPV (First Person View), operando em 5.8 GHz. A metodologia utilizada nessa pesquisa consiste em um levantamento teórico acerca das antenas de polarização circular, projetar, simular e construir estas antenas utilizando diferentes substratos a fim de verificar seu desempenho e embarcá-las em um sistema FPV. Os resultados obtidos através da simulação são comparados com os resultados experimentais a fim de atestar o modelo em questão com base na literatura empregada neste trabalho. Preliminarmente, os resultados simulados e medidos mostram que as Antenas Patch Triangular possuem todas as características desejáveis para operação no sistema FPV, sendo possível embarcá-las para a obtenção de imagens e análise de desempenho do sistema com as mesmas / 2018-06-11

Submitted by Vanessa Christiane (referencia@ufersa.edu.br) on 2018-05-02T18:24:47Z No. of bitstreams: 1 KaíckVOC_DISSERT.pdf: 2201549 bytes, checksum: 0aa156688ef6e55d0663212f326229e2 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2018-06-18T16:54:06Z (GMT) No. of bitstreams: 1 KaíckVOC_DISSERT.pdf: 2201549 bytes, checksum: 0aa156688ef6e55d0663212f326229e2 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2018-06-18T16:54:44Z (GMT) No. of bitstreams: 1 KaíckVOC_DISSERT.pdf: 2201549 bytes, checksum: 0aa156688ef6e55d0663212f326229e2 (MD5) / Made available in DSpace on 2018-06-18T16:55:00Z (GMT). No. of bitstreams: 1 KaíckVOC_DISSERT.pdf: 2201549 bytes, checksum: 0aa156688ef6e55d0663212f326229e2 (MD5) Previous issue date: 2018-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Microstrip antennas have a potential that was only initially studied in 1953, to receive more attention only in the 1970s. Since then, several techniques, methods of analysis, algorithms, and materials have been developed to study, understand and produce these antennas. Advantages such as low cost, small dimensions, low weight and volume, aerodynamically advantageous format, possibility to have flat or curved format made this antenna one of the most interesting for the military area, and now for commercial and industrial area. This work has as objective at the development of substrates for microfite antennas using Ni-Zn-type Ferrites using the Sol-Gel technique, a physicochemical process that allows the obtaining of nanometric particles, in view of the ease of execution of this technique. The experiments consisted in the production of three types of ferrites, NiFe2O4, ZnFe2O4 and Ni0,5Zn0,5Fe2O4 in which these pellets were used as substrates of the microfite antennas. Then, simulations were carried out using commercial HFSS software to verify the influence of the magnetic properties of the material on antenna parameters such as return loss, bandwidth, and Smith's chart. The simulated results were divided into groups called dielectric and standard, in which these groups differed in the presence or absence of the magnetic characteristics of the material. All the results were compared with the values measured and analyzed by verifying some effects such as the reduction of the resonance frequency of the antennas / As antenas de microfita têm um potencial que só foi inicialmente estudado em 1953, para receber mais atenção somente na década de 1970. Desde então foram desenvolvidas diversas técnicas, métodos de análises, algoritmos, e materiais com o intuito de estudar, compreender e produzir estas antenas. Vantagens como custo baixo, pequenas dimensões, baixo peso e volume, formato aerodinamicamente vantajoso, possibilidade de ter formato plano ou curvo fizeram desta antena uma das mais interessantes para a área militar, e agora para a área comercial e industrial. Este trabalho visou o desenvolvimento de substratos para as antenas de microfita utilizando Ferritas do tipo Ni-Zn através da técnica de Sol-Gel, um processo físico-químico que permite a obtenção de partículas nanométricas, tendo em vista a facilidade de execução dessa técnica. Os experimentos consistiram na produção de três tipos de pastilhas de Ferritas, NiFe2O4, ZnFe2O4 e Ni0,5Zn0,5Fe2O4 em que essas pastilhas foram utilizadas como substratos das antenas de microfita. Em seguida, foi realizado simulações, por meio do software comercial HFSS®, com o objetivo de verificar a influência das propriedades magnéticas do material em parâmetros das antenas como perda de retorno, largura de banda, carta de Smith. Os resultados simulados foram divididos em grupos chamados de dielétrico e padrão, no qual esses grupos se diferenciavam no tocante a presença ou não das características magnéticas do material. Todos os resultados foram comparados com os valores medidos e analisados verificando alguns efeitos como a redução da frequência de ressonância das antenas / 2018-05-02

A novel microstrip patch antenna topology is presented for achieving a dual-band response with arbitrarily closely spaced resonances. This topology is based on a coupled transmission line structure in order to take advantage of the separation in propagation constants for parallel (even-mode) and anti-parallel (odd-mode) current modes. Applying a metamaterials inspired design approach, periodic reactive load­ings are used to design the underlying transmission line to have specific propagation constants necessary to realize a desired separation between two resonant frequencies. Using a single probe feed for a finite coupled line segment, both even-and odd-mode resonances can be excited to radiate efficiently at their respective design frequencies. The efficiency of the odd-mode radiation is enhanced by separating the two lines, while strong coupling is maintained by inserting a series of narrowly-separated thin loops between them. Several example resonant antenna designs, in the 2.45 GHz band, are presented. The directivities of these microstrip patch antennas are enhanced by optimizing the physical length of the resonant structure. For a resonant antenna obtained by cas­cading several unit cells of reactively loaded microstrip segments, dispersion analysis is employed for the unit-cell design. Maximum directivity is achieved by choosing the overall physical length to be slightly less than a half wavelength in free space at the design frequency. This gain optimization is applied to three coupled-line antennas, as well as a single resonance patch. Excellent agreement is observed between simulated and measured responses across all designs. The potential of loading the coupled line structure with active components is also explored. Varactor diodes are placed on coupled-line structures in two configurations. In one configuration, both resonant frequencies are affected. In the other configura­tion, only the odd-mode characteristics are reconfigured. In this way, the resonant frequency of either one or both modes can be adjusted by applying a DC bias voltage to the varactor diode loading elements. Two antennas, one employing each of these topologies, were designed and fabricated. Control of the resonant frequency over the predicted range through applying a bias voltage is observed with the fabricated prototypes.

No description available.

The Finite-Difference Time-Domain (FDTD) method has gained tremendous popularity in the past decade as a tool for solving Maxwell's equations. Phased Array Antennas find several applications including mobile communications ( cellular, personal communication systems and networks), satellite communications, global positioning system (GPS), aeronautical and radar systems. This dissertation describes the application of the FDTD method for calculating broadband characteristics of finite-sized phased array antennas consisting of microstrip elements fed with coaxial probes. The characterization of such antennas is dependent upon the development of simulation tools that can accurately model general topologies including wires, dielectrics, conductors lumped elements and metallic strips. The use of these simulation tools reduces the cost and effort associated with fabricating and testing phased array antennas. The FDTD formulation is inherently broadband, very general, and easily accorrunodates arbitrary conductor geometry and dielectric configurations. The FDTD method is implemented and applied to determine the input impedance, radiation-patterns and gain of microstrip antennas. Next, the main contributions of this work are described which include the full time-domain characterization of broadband characteristics of finite-sized phased array antennas for different scan conditions. Active reflection coeffici nt gain scan-element patterns and scanning-array radiation patterns are calculated.

No description available.

A existência de ondas gravitacionais foi confirmada indiretamente pela observação astronômica de pulsares binários. Detectores de ondas gravitacionais tem sido desenvolvidos desde o trabalho pioneiro de Weber nos anos 60. Esforços estão sendo realizados no sentido de aumentar a sensibilidade dos detectores e realizar uma detecção direta, que ainda não foi confirmada. O Grupo GRAVITON está aperfeiçoando e melhorando a sensibilidade de um detector de ondas gravitacionais que se encontra no Laboratório de Estado Sólido e Baixas Temperaturas do Instituto de Física da Universidade de São Paulo (LESBT/IFUSP), na cidade de São Paulo com apoio da FAPESP (processo 2006/56041-3). Esse detector, denominado MARIO SCHENBERG, é composto por uma massa ressonante esférica de CuAl(6%) com 65 cm de diâmetro, com aproximadamente 1150 kg, que deverá atingir a sensibilidade h ~ 10-22 em uma banda passante de 50 Hz, em torno de 3200 Hz, quando estiver operando a temperaturas da ordem de 0,05 K. Atualmente o detector já tem toda a sua infraestrutura criogênica montada e testada para resfriamentos a 4 K e toda a suspensão da esfera bem como todo o sistema de filtragem mecânica construídos e montados. Já foram realizadas as primeiras corridas comissionadas em 2006, 2007 e 2008, quando foram realizados vários diagnósticos sobre o sistema e desde então vem sendo desenvolvidos os transdutores para colocar o detector novamente em operação com melhor sensibilidade. Paralelamente, foram realizadas melhorias no próprio detector em razão dos diagnósticos realizados. O trabalho aqui apresentado está associado ao projeto acima. O autor desenvolveu atividades associadas à construção e desenvolvimentos do detector, que podem ser divididas em três partes principais: na parte mecânica, foi desenvolvido, instalado e testado um novo sistema de isolamento vibracional da suspensão da esfera; na parte criogênica foram feitas novas conexões térmicas, cálculos de gastos de hélio líquido e feitos desenvolvimentos para o funcionamento do refrigerador por diluição; e na parte eletrônica foi feita a instalação da eletrônica responsável pela transdução do sinal, além do desenvolvimento de um novo par de antenas de microfita. / The existence of gravitational waves has been confirmed indirectly by astronomical observation of binary pulsars. Gravitational wave detectors have been developed since the pioneering work of Weber in the 60s. Efforts are being made to increase the sensitivity of the detectors and perform a direct detection, wich has not been confirmed yet. The GRAVITON Group is enhancing and improving the sensitivity of a gravitational wave detector which is at the Laboratório de Estado Sólido e Baixas Temperaturas of the Instituto de Física of the Universidade de São Paulo (LESBT / IFUSP), in São Paulo city and is supported by FAPESP (processo 2006/56041-3). This detector, called MARIO SCHENBERG, consists of a spherical resonant mass of CuAl (6%) with 65 cm in diameter, and approximately 1150 kg, which should reach the sensitivity of h ~ 10-22 in a bandwidth of 50 Hz around 3200 Hz, when operating at temperatures of 0.05 K. Currently the detector already has all its infrastructure assembled and tested for cryogenic cooling down to 4 K and the whole suspension of the sphere as well as all mechanical isolation system constructed and assembled. Commissioning runs have already been done in 2006, 2007 and 2008, when several diagnoses on the system were performed and since then there have been many developments on the transducers to put back the detector into operation with improved sensitivity. At the same time, improvements have been made within the detector itself due to the diagnoses. The work presented here is associated with the above project. The author has developed activities and developments associated with the detector construction, which can be divided into three main parts: the mechanical part, in which a new system of vibration isolation was designed for the sphere suspension, installed and tested; the cryogenic part, in which new connections and thermal calculations of liquid helium boil-off rate were made as well as other developments for the operation of a dilution refrigerator; and the electronic part, in which the installation of the electronic signal responsable for the transduction was made, besides the development of a new pair of micro-strip antenna.

The designs of various feeding networks for microstrip antennas have been investigated in this dissertation. In the active microstrip antenna designs, an amplifier-type microstrip antenna integrates a two- port amplifier circuitry to the various passive antennas through a 50£[ inset microstrip feed line which can function in broadband operation¡ACP operation and dual-frequency operation. As for the broadband circularly polarized microstrip antenna with a dual-perpendicular feed design, antenna with a dual-perpendicular feed which was formed by a Wilkinson power divider with a quarter-wavelength section of microstrip line for providing equal splitting of the input power and 90¢X phase difference to the two feed points has been presented. The broadband CP bandwidth can be achieved due to the good isolation between the two output lines of the feed network. In the microstrip antennas with CPW feed designs, we first proposed a microstrip antenna with three-dimensional CPW feed. A separate feed substrate is used which can provide a large-area space for the layout of complicated microwave circuitry. In addition, the feed substrate can also be oriented to the patch substrate with various angles, resulting in more flexibility in the proposed three-dimensional feed design. Finally, we proposed a design with two slot lines located at both sides of the coupling slot which can lengthen the excited patch surface current path, thus the resonant frequency is reduced and an antenna size reduction up to 40% has been obtained.

The Method of Moments (MoM) has been used extensively to solve electromagnetic problems. Its popularity is largely attributed to its adaptability to structures with various shapes and success in predicting the equivalent induced currents accurately. However, due to its dense matrix, especially for large structures, the MoM suffers from long matrix solution time and large storage requirement. In this thesis it is shown that use of wavelet basis functions result in a MoM matrix which is sparser than the one obtained by using traditional basis functions. A new wavelet system, different from the ones found in literature, is proposed. Stabilized Bi-Conjugate Gradient Method which is an iterative matrix solution method is utilized to solve the resulting sparse matrix equation. Both a one-dimensional problem with a microstrip line example and a two-dimensional problem with a rectangular patch antenna example are studied and the results are compared.

This thesis presents the design, fabrication, and measurement of tunable frequency microstrip antennas using RF MEMS (Microelectromechanical Systems) technology. The integration of RF MEMS components with radiators enable to implement tunable systems due to the adjustable characteristics of RF MEMS components. In the frame of this thesis, different types of structures have been investigated and designed. The first structure consists of a microstrip patch antenna which is loaded with a microstrip stub whose length is controlled by RF MEMS switches. In the other structure, the length of a microstrip patch antenna is changed by connecting a metal plate using RF MEMS switches. The third structure is composed of a microstrip patch antenna and a microstrip stub on which RF MEMS variable capacitors are placed periodically to control the resonant frequency. In order to maintain an easier integration with RF MEMS capacitors, another structure consisting of a microstrip patch antenna and a coplanar waveguide (CPW) stub which is loaded with variable RF MEMS capacitors is designed. The final structure is a dual frequency CPW-fed rectangular slot antenna whose resonant frequencies are shifted by RF MEMS variable capacitors placed on a short circuited stub inserted inwards the antenna. The fabrication of CPW-fed rectangular slot antenna is completed in the MEMS fabrication facilities of METU using RF MEMS process based on electroforming on glass substrate. The measurement results show that RF MEMS components might be a proper solution to obtain tunable frequency antenna structures.