Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-07-04T19:21:04Z No. of bitstreams: 1 JoséAPM_DISSERT.pdf: 11175477 bytes, checksum: 06a97520ecfb91560a5b33b0a7a17ca7 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-07-18T15:03:31Z (GMT) No. of bitstreams: 1 JoséAPM_DISSERT.pdf: 11175477 bytes, checksum: 06a97520ecfb91560a5b33b0a7a17ca7 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-07-18T15:06:43Z (GMT) No. of bitstreams: 1 JoséAPM_DISSERT.pdf: 11175477 bytes, checksum: 06a97520ecfb91560a5b33b0a7a17ca7 (MD5) / Made available in DSpace on 2017-07-18T15:07:07Z (GMT). No. of bitstreams: 1 JoséAPM_DISSERT.pdf: 11175477 bytes, checksum: 06a97520ecfb91560a5b33b0a7a17ca7 (MD5) Previous issue date: 2016-12-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The complexity of communication systems drives researches into new types of cheaper and more efficient antennas. Microstrip antennas are planar structures that can be used in various types of applications due to their peculiar characteristics. There are several techniques in the literature to improve the performance of these antennas, among them the use of metasurfaces. The working principle of these structures is similar to a metamaterial, based on constitutive properties, permissiveness and permeability, which are not found in materials in nature, resulting in a negative refractive index. The present work has the objective of analyzing the application of metasurfaces in planar antennas in the range of microwaves, in the frequencies of 1 to 10 GHz that comprise the bands L, S, C and part of band X, through the application of rectangular and circular SRR structures in the patch and ground plane of the antennas. The structures were divided into sizes λ/10, λ/15 and λ/20. The antennas were first analyzed by means of simulation with the commercial software HFSS®, with the simulated results were selected four antennas for manufacturing, of which the measured results of the parameters were obtained in a vector network analyzer, namely: loss of return, Gain and impedance matching. The results of the antennas manufactured were in agreement with the simulations / A complexidade dos sistemas de comunicação impulsionam as pesquisas por novos tipos de antenas mais baratas e eficientes. Antenas de microfita são estruturas planares que podem ser utilizadas em vários tipos de aplicações devido as suas características peculiares. Existem na literatura várias técnicas para melhorar o rendimento dessas antenas, dentre elas se destaca o uso das Metassuperfícies. O princípio de funcionamento dessas estruturas é similar ao de um metamaterial, baseiam-se nas propriedades constitutivas, permissividade e permeabilidade, que não são encontrados em materiais na natureza, resultando em um índice de refração negativo. O presente trabalho tem por objetivo analisar a aplicação de estruturas Metassuperfície em antenas planares na faixa de micro-ondas, nas frequências de 1 a 10 GHz que compreendem as bandas L, S, C e parte da banda X, mediante a aplicação das estruturas SRR do tipo retangular e circular no patch e no plano de terra das antenas, as estruturas foram divididas nos tamanhos λ/10, λ/15 e λ/20. As antenas foram primeiramente analisadas por meio de simulação com o software comercial HFSS®, com os resultados simulados foram selecionadas quatro antenas para fabricação, das quais os resultados medidos dos parâmetros foram obtidos em um analisador de redes vetoriais, a saber: perda de retorno, ganho e casamento de impedância. Os resultados das antenas fabricadas apresentaram concordância com as simulações / 2017-07-04

Made available in DSpace on 2014-12-17T14:55:54Z (GMT). No. of bitstreams: 1 VitorFB_DISSERT.pdf: 3545980 bytes, checksum: 2759df31b3e705a93ae644db95f0c01f (MD5) Previous issue date: 2012-02-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Microstrip antennas are subject matter in several research fields due to its numerous advantages. The discovery, at 1999, of a new class of materials called metamaterials - usually composed of metallic elements immersed in a dielectric medium, have attracted the attention of the scientific community, due to its electromagnetic properties, especially the ability to use in planar structures, such as microstrip, without interfering with their traditional geometry. The aim of this paper is to analyze the effects of one and bidimensional metamaterial substrates in microstrip antennas, with different configurations of resonance rings, SRR, in the dielectric layer. Fractal geometry is applied to these rings, in seeking to verify a multiband behavior and to reduce the resonance frequency of the antennas. The results are then given by commercial software Ansoft HFSS, used for precise analysis of the electromagnetic behavior of antennas by Finite Element Method (FEM). To reach it, this essay will first perform a literature study on fractal geometry and its generative process. This paper also presents an analysis of microstrip antennas, with emphasis on addressing different types of substrates as part of its electric and magnetic anisotropic behavior. It s performed too an approach on metamaterials and their unique properties / As antenas de microfita s?o objeto de estudo em diversos campos de pesquisa devido a suas in?meras vantagens. A obten??o, em 1999, de uma nova classe de materiais, chamados metamateriais - normalmente compostos por elementos met?licos imersos em um meio diel?trico, tem atra?do a aten??o da comunidade cient?fica, gra?as ?s suas propriedades eletromagn?ticas e, principalmente, pela capacidade de utiliza??o em estruturas planares, tais como a microfita, sem interferir em sua geometria tradicional. O objetivo desse trabalho ? analisar os efeitos do uso de substratos metamateriais uni e bidimensionais em antenas de microfita, com diferentes configura??es de an?is de resson?ncia - SRR - na camada diel?trica. A geometria fractal ? aplicada a esses an?is, na busca de se verificar um comportamento multibanda e de se reduzir a frequ?ncia de resson?ncia das antenas. Os resultados s?o, ent?o, obtidos com o software comercial Ansoft HFSS, usado para a an?lise do comportamento eletromagn?tico das antenas, por meio do M?todo dos Elementos Finitos (FEM). Para tanto, nessa disserta??o, ? previamente realizado um estudo bibliogr?fico sobre a geometria fractal e seu processo gerador. Este trabalho apresenta tamb?m uma an?lise sobre as antenas de microfita, com ?nfase ? abordagem de diferentes tipos de substratos, evidenciando seu comportamento anisotr?pico el?trico e magn?tico. ? realizada, ainda, uma abordagem sobre os metamateriais e suas propriedades singulares

<p>The objectives of this investigation were to experimentally and analytically evaluate the  performance of a valve train cam and oscillating roller follower mechanism. Of particular interest  was the effect of operating conditions on the slide-to-roll ratio (SRR) of the roller follower. In order to experimentally measure the SRR at the cam-roller contact, a valve train test rig  (VTTR) was utilized. The VTTR contained a section of a heavy-duty diesel engine valve train that  was instrumented with encoders and Hall effect sensors to measure the camshaft and roller  follower angular velocities as a function of operating parameters.  To corroborate the experimental with analytical results, a numerical model for the cam and  oscillating roller follower was developed. In this modeling approach, the roller angular velocity  was determined via a torque balance between the frictional torque of the pin-roller follower and  cam-roller follower interfaces. The pin-roller friction was obtained by developing a time-dependent hydrodynamic journal bearing model with variable speed and load. Friction maps were  developed for the cam-roller follower interface using a ball-on-disk EHD2 rig to capture the  friction behavior across a range of entraining velocities, contact pressures, and SRRs. Additional  areas of investigation included thermal effects and wear in the pin-roller contact. Overall, good agreement was obtained between the experimental and analytical roller  follower angular velocity, with the normalized RMS errors less than 7%, across all operating  conditions investigated. The analytical investigation determined that thermal effects in the pin-roller contact are insignificant for the typical operating conditions. However, it was shown that the  pin-roller friction torque is critical in causing roller follower slip, as the SRR greatly increases  once the pin-roller friction torque is greater than the cam-roller friction torque. Finally, pin-roller  local wear was demonstrated to have detrimental effects on the SRR of the roller follower once a  critical wear depth was reached. </p>

Yes / This article presents a miniaturized triple-band antenna for Internet of Things (IoT) applications. The miniaturization is achieved by using a split square ring resonator and half ring resonator. The antenna is fabricated on an FR4 substrate with dimensions of (33 × 22 × 1.6) mm3. The proposed antenna resonates at the frequencies 2.4 GHz, 3.7 GHz, and 5.8 GHz for WLAN and WiMax applications. The obtained −10 dB bandwidth for the three bands of the proposed antenna are 300 MHz, 360 MHz, and 900 MHz, respectively. The measured reflection coefficient values of the proposed antenna corresponding to each resonant frequency are equal to −14.772 dB, −20.971 dB, and −28.1755 dB, respectively. The measured gain values are 1.43 dBi, 0.89 dBi, and 1 dBi, respectively, at each resonant frequency. There is a good agreement between the measured and simulated results, and both show an omnidirectional radiation pattern at each of the antenna resonant frequencies that is suitable for IoT portable devices.

Split ring resonator (SRR) is a metamaterial structure which displays negative permeability values over a relatively small bandwidth around its magnetic resonance frequency. Unit SRR cells and arrays have been used in various novel applications including the design of miniaturized microwave devices and antennas. When the SRR arrays are combined with the arrays of conducting wires, left handed materials can be constructed with the unusual property of having negative valued effective refractive indices. In this thesis, unit cells and arrays of single-ring multiple-split type SRR structures are numerically analyzed by using Ansoft&rsquo / s HFSS software that is based on the finite elements method (FEM). Some of these structures are constructed over low-loss dielectric substrates and their complex scattering parameters are measured to verify the numerical simulation results. The major purpose of this study has been to establish equivalent circuit models to estimate the behavior of SRR structures in a simple and computationally efficient manner. For this purpose, individual single ring SRR cells with multiple splits are modeled by appropriate two-port RLC resonant circuits paying special attention to conductor and dielectric loss effects. Results obtained from these models are compared with the results of HFSS simulations which use either PEC/PMC (perfect electric conductor/perfect magnetic conductor) type or perfectly matched layer (PML) type boundary conditions. Interactions between the elements of SRR arrays such as the mutual inductance and capacitance effects as well as additional dielectric losses are also modeled by proper two-port equivalent circuits to describe the overall array behavior and to compute the associated transmission spectrum by simple MATLAB codes. Results of numerical HFSS simulations, equivalent circuit model computations and measurements are shown to be in good agreement.

This thesis addresses the design study, implementation and analysis of signal processing algorithms for a 79 GHz millimeter-wave Phase Modulated Continuous Wave (PMCW) Multi Input Multi Output (MIMO) short range radar; performed in IMEC research institute (Leuven, Belgium). The radar system targets high resolution performance with low power consumption in order to integrate a full MIMO radar transceiver with digital processor and antennas in a compact package featuring a size of 1 cm2. Achieving such radar system characteristics requires the exploitation of a highly demanding digital architecture with signal processing gain and high range, speed and angle resolutions. The improved resolution and detection capabilities will be achieved by performing signal processing algorithms on the reflected waveform. The digital front-end implements parallel range gate processing with a bank of correlators that perform: pulse compression, coherent accumulation to further increase Signal to Noise Ratio (SNR) and N-point FFT to extract the Doppler information. The use of MIMO is proposed implementing a code domain technique in the PMCW waveform, the Outer Hadamard Code MIMO. This concept makes use of a unique sequence for all the transmitting antennas that is rendered by an outer sequence to ensure the orthogonality of the transmitted waveforms. The outer code makes use of the good cross-correlation properties of the Hadamard sequences and the waveform uses sequences that exhibit perfect auto-correlation profile, the Almost Perfect Autocorrelation Sequences (APAS). The MIMO implementation results in higher angular resolution and extra processing gain. The use of beamforming techniques in the radar allows the angle estimation of the detected targets; using rough and fine beamforming that provides with coarse and precise Angle of Arrival (AoA) estimation in an early and late stage respectively. A Constant False Alarm Rate (CFAR) processing stage is implemented in the stage of the system where higher signal processing gain is achieved. This algorithm allows the variation of the CFAR parameters and analyzes the detections in order to improve the probability of detection (Pd) while decreasing the probability of false alarm (Pfa). A series of simulations with different scenarios and variable parameters are set in order to analyze the performance of the system. The simulations analyze the gain achieved in each stage and their outcomes show an impressive processing gain that can reach SNR improvements as high as 77 dB for a small virtual array while keeping the Pfa low with the CFAR adjustment. The use of bigger arrays demonstrates the possibility to enable clear detections for low Radar Cross Section (RCS) targets in far distances of the unambiguous range. The use of beamforming shows interference reduction improvement as the beam widths narrow with the increasing number of virtual array antennas. These results have been achieved while keeping the system design parameters to a range resolution of 7.5 cm for a maximum range of 37.5 meters with speed resolution of 0.2 m/s and a maximum detectable speed of 12.66 m/s. The outcomes support the good performance of the signal processing techniques implemented and the benefits in applying them in a SoC mmWave MIMO radar.

Yes / Empirical results of an electrically small printed monopole antenna is described with fractional bandwidth of 185% (115 MHz–2.90 GHz) for return-loss better than 10 dB, peak gain and radiation efficiency at 1.45 GHz of 2.35 dBi and 78.8%, respectively. The antenna geometry can be approximated to a back-to-back triangular shaped patch structure that is excited through a common feed-line with a meander-line T-shape divider. The truncated ground-plane includes a central stub located underneath the feed-line. The impedance bandwidth of the antenna is enhanced with the inclusion of meander-line slots in the patch and four double split-ring resonators on the underside of the radiating patches. The antenna radiates approximately omnidirectionally to provide coverage over a large part of VHF, whole of UHF, entire of L-band and some parts of S-band. The antenna has dimensions of 48.32×43.72×0.8 mm3, which is corresponding with the electrical size of 0.235λ_0×0.211λ_0×0.003λ_0, where λ_0 is free-space wavelength at 1.45 GHz. The proposed low-profile low-cost antenna is suitable for application in wideband wireless communications systems. / H2020-MSCA-ITN-2016 SECRET-722424 and UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1

Metamaterials attracted significant attention in recent years due to their potential to create novel devices that exhibit specific electromagnetic properties. In this thesis, we investigated transmission and propagation properties of novel metamaterial structures. Electromagnetic properties of metamaterials are characterized and the resonance mechanism of Split Ring Resonator (SRR) structure is investigated. Furthermore, a recent lefthanded metamaterial structure for microwave regime called Fishnet-type metamaterial is studied. We demonstrated the left-handed transmission and negative phase velocity in Fishnet Structures. Finally, we proposed and successfully demonstrated novel approaches that utilize the resonant behavior of SRR structures to enhance the transmission of electromagnetic waves through sub-wavelength apertures at microwave frequency regime. We investigated the transmission enhancement of electromagnetic waves through a sub-wavelength aperture by placing SRR structures in front of the aperture and also by changing the aperture shape as SRR-shaped apertures. The incident electromagnetic wave is effectively coupled to the sub-wavelength aperture causing a strong localization of electromagnetic field in the sub-wavelength aperture. Localized electromagnetic wave gives rise to enhanced transmission from a single sub-wavelength aperture. The proposed structures are designed, simulated, fabricated and measured. The simulations and experimental results are in good agreement and shows significant enhancement of electromagnetic wave transmission through sub-wavelength apertures by utilizing proposed novel structures. Radius (r) of the sub-wavelength aperture is approximately twenty times smaller than the incident wavelength (r/&amp / #955 / ~0.05). This is the smallest aperture size to wavelength ratio in the contemporary literature according to our knowledge.

Actuellement, les applications sans fils connaissent une croissance importante. La multiplication de leurs standards (LTE, 3G, Wifi, Bluetooth, GPS) incite les chercheurs à réduire d'avantage l'encombrement, la consommation d'énergie et les coûts. Notre travail présente une exploration théorique et expérimentale des techniques qui permettent d'atteindre cet objectif : les métamatériaux permettent la miniaturisation des circuits et les MEMS RF ou les matériaux ferroélectriques permettent leur accordabilité en fréquence. Après un rappel théorique des métamatériaux, nous avons étudié expérimentalement des structures planaires en PCB pour mettre en évidence les propriétés du diagramme de dispersion. Nous avons ensuite conçu un filtre passe-bande destiné à une application spatiale, l'utilisation des métamatériaux a permis de réduire son encombrement d'environ 90% par rapport à un filtre classique à stub quart d'onde. En utilisant la technologie silicium, nous nous sommes ensuite intéressés à l'optimisation d'une cellule CRLH pour augmenter son degré de liberté en ajoutant un stub capacitif. Ce travail est complété par l'introduction des MEMS pour apporter une agilité à la structure. Les résultats expérimentaux ont permis d'exhiber une accordabilité d'environ 80%. Dans le même sens, le BST (matériau ferroélectrique) a été exploré, des circuits de test ont été réalisés pour extraire ses caractéristiques. Les travaux expérimentaux ont exhibé des accordabilités allant jusqu'à 67%. Cette étude a été complétée par la réalisation de structures métamatériaux accordables.

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