Orientador: Luiz Carlos Kretly / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-24T13:36:57Z (GMT). No. of bitstreams: 1 Silva_MauricioWeberBenjoda_D.pdf: 10953654 bytes, checksum: 6b4d1b6000f187a807b5cec8ba653713 (MD5) Previous issue date: 2014 / Resumo: Neste trabalho, as diferentes propriedades de superfícies seletivas em frequência, FSS - Frequency Selective Surfaces, são analisadas. As FSS são estruturas planares com células periódicas e podem ser classificadas como uma classe de metamateriais. Para tanto, o mecanismo de trabalho dessas estruturas foi extensivamente estudado, e um método próprio, baseado no modelo de circuito equivalente em conjunto com simulações de onda completa foi proposto. A ferramenta desenvolvida é útil para uma análise preliminar rápida de FSS, a qual foi utilizada para criar uma base de dados de elementos conhecidos na literatura. Diferente dos modelos de análise clássicos, a modelagem analítica proposta, que é uma das principais contribuições do trabalho, usa um simples algoritmo para aproximar a resposta de superfícies seletivas em frequência com geometrias arbitrárias, para incidências normal e oblíqua e para substratos com quaisquer espessuras. Nesse sentido, após a simulação eletromagnética da estrutura, é possível computar a resposta de uma FSS com diferentes parâmetros sem o consumo de tempo das simulações de onda completa. O modelo usa as características peculiares de superfícies de alta impedância, HIS - High Impedance Surface, que dentro de determina faixa comporta-se como condutor magnético perfeito, PMC - Perfect Magnetic Conductor, enquanto no restante da banda tem comportamento de um condutor elétrico perfeito, PEC - Perfect Electric Conductor, para sintetizar absorvedores finos e planares de micro-ondas. As estruturas, compostas de superfície seletiva em frequência resistivas sobre um substrato dielétrico aterrado, são projetadas visando aplicação em diferentes faixas de frequência de absorção e diferentes larguras de banda. Na faixa de 5,5 GHz, objetivou-se satisfazer as especificações dos sistemas WIMAX, WLAN, com os padrões IEEE 802.11a, bem como sistemas de radar, enquanto sinais de outras faixas podem trafegar com atenuação mínima ou nula. Para a faixa mais elevada, projetou-se uma estrutura que oferece absorção sobre a faixa de frequências de 10 GHz a 18 GHz, que pode ser empregada visando aplicações na banda-X e banda-Ku. O método de modelagem para a FSS e para os absorvedores propostos foi validado fisicamente através de montagens experimentais e instrumentação, especialmente desenvolvidas para estas estruturas. Os protótipos dos absorvedores fabricados são extremamente finos e foram medidos por meio de setups de medida em campo aberto e em câmara anecóica. As estruturas projetadas mostraram excelente desempenho para as faixas medidas, mantendo refletividade tipicamente abaixo de -10 dB ao longo de toda a banda. A metodologia desenvolvida nesta pesquisa pode ser ampliada para diferentes faixas de frequências, larguras de banda e aplicações / Abstract: In this work, the different properties of frequency selective surfaces - FSS are analyzed. Frequency selective surfaces are planar structures with periodic cells and can be classified as a kind of metamaterials. To this end, the working mechanism of these structures has been extensively studied, and a proper method based on the equivalent circuit model in conjunction with full-wave simulations was proposed. The developed tool is useful for a fast preliminary analysis of FSS, which was used to create a database of known elements presented in the literature. Unlike of classical analysis model, the proposed analytical modeling, which is one of the main thesis contributions, uses a simple algorithm for approximate the response of frequency selective surfaces with arbitrary shape, for normal and oblique incidence and for substrates with all thicknesses. In this sense, after the electromagnetic simulation of the structure, it is possible to compute the response of an FSS with different parameters without the time consuming full-wave simulations. The model uses the unique characteristics of High-Impedance Surfaces - HIS, which for certain frequency range, behaves as Perfect Magnetic Conductor - PMC, while outside this band behaves as a Perfect Electric Conductor - PEC, for synthesizing thin planar microwave absorbers. The structures, comprising resistive frequency selective surfaces over a grounded dielectric substrate, are designed aiming different absorption frequency bands and different bandwidths. In the 5.5 GHz frequency range, the aim was to satisfy the specifications of WiMAX, WLAN systems, in view of the IEEE 802.11a standards, as well as radar systems, while signals from other bands can travel across with zero or minimal attenuation. To the highest range, the designed structure provides absorption over 10 GHz to 18 GHz frequency range, and can be applied to the X- and Ku- band. The modeling method for the FSS and the proposed absorbers was physically validated through experimental setups and instrumentation, especially developed for these structures. The prototype of the fabricated absorbers are extremely thin and were characterized by using free space and anechoic chamber measurement setups. The designed structures showed excellent performance for measurements ranges, with reflectivity typically below -10 dB over the entire band. The methodology developed in this research can be extended to different frequency bands, bandwidth and applications / Doutorado / Eletrônica, Microeletrônica e Optoeletrônica / Doutor em Engenharia Elétrica

Bolometers are the most sensitive detectors for measuring millimeter and submillimeter wavelength astrophysical signals. Cameras comprised of arrays of bolometers have already made significant contributions to the field of astronomy. A challenge for bolometer cameras is obtaining observations at multiple wavelengths. Traditionally, observing in multiple bands requires a partial disassembly of the instrument to replace bandpass filters, a task which prevents immediate spectral interrogation of a source. More complex cameras have been constructed to observe in several bands using beam splitters and dichroic filters, but the added complexity leads to physically larger instruments with reduced efficiencies. The SPEctral Energy Distribution camera (SPEED) is a new type of bolometer camera designed to efficiently observe in multiple wavebands without the need for excess bandpass filters and beam splitters. SPEED is a ground-based millimeter-wave bolometer camera designed to observe at 2.1, 1.3, 1.1, and 0.85 mm simultaneously. SPEED makes use of a new type of bolometer, the frequency selective bolometer (FSB), to observe all of the wavebands within each of the camera's four pixels. FSBs incorporate frequency selective dipole surfaces as absorbing elements allowing each detector to absorb a single, narrow band of radiation and pass all other radiation with low loss. Each FSB also contains a superconducting transition-edge sensor (TES) that acts as a sensitive thermistor for measuring the temperature of the FSB. This thesis describes the development of the SPEED camera and FSB detectors. The design of the detectors used in the instrument is described as well as the the general optical performance of frequency selective dipole surfaces. Laboratory results of both the optical and thermal properties of millimeter-wave FSBs are also presented. The SPEED instrument and its components are highlighted and the optical design of the optics which couple SPEED to the Heinrich Hertz Telescope is given. This thesis concludes with an introduction to the jiggle mapping data analysis of bolometer instruments like SPEED.

No description available.

"March, 2009". / Thesis (PhD)--Macquarie University, Faculty of Science, Dept. of Physics & Engineering, 2008. / Bibliography: p. 145-158. / Introduction -- Frequency selective surfaces -- Absorb/transmit frequency selective surface absorber -- Switchable frequency selective surface for wireless applications -- Energy-saving glass characterisation -- Frequency selective surface solution for energy-saving glass -- Conclusion. / This thesis presents three topics related to frequency selective surfaces (FSSs), namely bsorb/transmit FSSs, active FSSs and passive bandpass FSSs for energy-saving glass used in modern buildings. These three FSSs are unique in their design and functionalities. The absorb/transmit FSS is a novel dual-layer frequency selective surface for 5 GHz WLAN applications. This FSS can stop propagation of specific bands by absorbing as opposed to re ecting, while passing other useful signals. This is in contrast to the conventional Salisbury and Jaumann absorbers, which provide good absorption in the desired band while the out-of-band frequencies are attenuated. The second topic is a single-layer bandpass active FSS that can be switched between ON and OFF states to control the transmission in 2.45 GHz WLAN applications. Previously, researchers have focused on the bandstop and dual-layer versions of the active FSS. This is in contrast to the design presented in this thesis which is single-layer and provides extra advantage in a practical WLAN environment. Also the dc biasing techniques that were used for the active FSS design are easier to implement and provide good frequency stability for different angles of incidence and polarisations in both ON and OFF states. The last topic is on the use of a bandpass FSS in energy-saving glass panels used in building design. The manufacturers of these glass panels apply a very thin metal-oxide coating on one side of the glass panels to provide extra infrared (heat) attenuation. However, due to the presence of the coating, these energy-saving glass panels also attenuate communication signals such as GSM 900, GSM 1800/1900, UMTS and 3G mobile signals etc. This creates a major communication problem when buildings are constructed with windows of this glass. In this thesis, a solution to this problem is presented by designing and etching a cross-dipole bandpass FSS on the coated side of the glass to pass the useful signals while keeping infrared attenuation at an acceptable level. One of the advantages of this FSS design is that measured material values of the metal-oxide coating are used for simulations, which have not been done previously. / Mode of access: World Wide Web. / 166 p. ill. (some col.)

Solar energy is increasingly being considered a promising solution to reduce the emissions of CO2 and green house gas. The performance of solar collectors largely depends on the ability to absorb incoming solar radiation with minimal thermal radiation losses. To weigh the potential absorbed energy to thermal losses, the performance criterion (PC) can be used, calculated as PC =α−xε, where α is absorptance, ε is emittance and x is a scaling factor < 1. It has been shown by G. Vargas et al. that Co-Cr alloys excibit great potential (α = 0.98 and ε = 0.03) for use in solar concentrators. The main goal of this project is to quantify the impact of key factors (controlled input variables) on an electroplating process of Co-Cr alloys, using the design of experiment (DOE) methodology. It is part of an ongoing collaboration between Absolicon and the physics department at Umeå university. Six factors were investigated using a fractional factorial (FrF) design. Data was collected through a series of experiments where stainless steel substrates were electroplated with Co-Cr alloys. The resulting samples were analyzed in terms of α and ε as well as the quality of deposition (QD). Using the experimental results, three models were made in a DOE-software called MODDE. Models are used to correlate the factors with each response, i.e. α, ε and QD. Ideally the predictive power of the models (Q2) should be as high as possible, and at least > 0.5. The analysis of variance (ANOVA) test was used to determine the significance of the models. Based on the models, the ’Optimizer’ tool in MODDE was used to predict two set of optimum factor settings, producing two samples, S1 and S2. S1 and S2 were evaluated in terms of α, ε and QD as well as chemical composition and structural properties of the coatings. The predictive power of the models was 0.49 for α, 0.38 for ε and 0.53 for QD. The predictive power of the models were therefore limited. ANOVA-test showed that the models for α and QD were statistically significant. For all three responses the significant effects were mostly two factor interactions. All three models showed significant lack of fit (model error) as a result of high reproducibility. S1 had the best PCAbsolicon (performance criterion for Absolicons solar collectors) of all samples with 0.858. S2 was not as good, even though it was predicted to have a higher value of PCAbsolicon by MODDE. EDS, XPS and SEM measurements of samples S1 and S2 showed that the two samples were very similar in terms of chemical composition. The main difference was that the coating of S1 was more porous, and also thicker than S2, 0.81 μm compared to 0.26 μm. Even though the models showed some predictive capabilities, the impact of the factors could not be fully determined. That is due to the nature of the FrF-design, which cannot accurately determine two-factor interactions.

Les surfaces sélectives en fréquence (FSS) pour la furtivité radar ou l’optique ont été largement étudiées. Depuis plus de vingt ans, des matériaux artificiels ont été conçus, permettant d’obtenir des propriétés particulières, notamment l’existence de bandes permises ou interdites, réfraction négative, ultra-réfraction. Par ailleurs, des antennes basées sur la mise en réseau d’un élément rayonnant sont plus compactes et plus facilement intégrables. Le problème de la diffraction d’une onde plane par des réseaux tridimensionnels bipériodiques peut être résolu par éléments finis ou par équations intégrales bipériodiques ; il l’est souvent par une méthode hybride combinant la méthode des éléments finis et la méthode aux équations intégrales. Nous avons choisi de développer une méthode hybride utilisant deux variantes de la méthode aux équations intégrales. Les domaines semi-infinis (l’extérieur du réseau) sont traités par des équations intégrales bipériodiques (EI3D2D), et les domaines bornés (l’intérieur du réseau) sont traités par des équations intégrales tridimensionnelles (EI3D), auxquelles on impose des conditions aux limites de pseudopériodicité. Ce code numérique est développé dans le cadre du code SPECTRE de Dassault-Aviation, qui est un code généraliste 3D, afin de bénéficier de la richesse des modèles qui y ont déjà été développés (modèle composé d’un nombre quelconque de sous-domaines de formes et de matériaux quelconques, traitement des différents cas de jonctions entre sous-domaines, matériaux de faible épaisseur). L’efficacité en termes de précision et en temps de calcul de la méthode numérique est validée par comparaison des résultats avec d’autres simulations numériques et également avec des résultats de mesures. Les cas testés sont représentatifs de plusieurs des principaux phénomènes liés aux métamatériaux : surfaces sélectives en fréquence, transmission « extraordinaire », surfaces à haute impédance. Enfin, nous étudions un radôme passe-bande indépendant à l’angle d’incidence, à l’aide de la méthode numérique que nous proposons. La structure retenue se base sur un réseau de cavités coaxiales dans une couche métallique. Nous expliquons l’origine physique des résonances qui apparaissent et nous suggérons une évolution géométrique du profil des cavités, afin d’augmenter la largeur de bande passante. / Frequency selective surfaces (FSS) for radar stealth or in optics have been widely studied. For more than two decades, articial materials have been designed to highlight specific behaviour, like the existence of allowed or forbidden bands, negative refraction, ultra-refraction... Moreover, antennas based upon an array of radiating elements improve the compactness and integration of these features. The problem of the diffraction of a plane wave by 3D biperiodic scatterers can be solved by finite-elements methods (FEM) or biperiodic boundary integral equations (BIE). It is often done by hybrid methods, that combine FEM and BIE. We choose to develop a hybrid method that uses two variants of the BIE method. Semiinfinite outer domains are treated by biperiodic integral equations (3D2D IE) and inner bounded domains are treated by 3D free-space integral equations (3D IE). Pseudoperiodic boundary conditions are enforced in the scattering biperiodic structure. The numerical code is developed in the framework of Dassault Aviation’s SPECTRE code, which is a general 3D code, in order to take advantage of the various models that have already been developed : arbitrary number of sub-domains of various shapes or materials, treatment of the different types of junctions between sub-domains, thin slabs. The efficiency in terms of accuracy and computation time of the numerical code is validated by comparison of the results from other numerical simulations or measurements. All the test cases are representative of several of the main phenomena that can be observed in metamaterials : FSS, “extraordinary” transmission, high-impedance surfaces. Finally, a bandpass radome which is independent to the angle of incidence is studied. The proposed numerical method is used. The chosen structure is based upon an array of coaxial cavities in a metallic slab. We explain the physical origin of resonances that appear and we suggest a geometrical evolution of the profile of the cavities, to favor a wideband behavior.

Thesis (PhD)--Macquarie University, Faculty of Science, Dept. of Physics & Engineering, 2008. / "March, 2009". Bibliography: p. 145-158.

Made available in DSpace on 2014-12-17T14:55:39Z (GMT). No. of bitstreams: 1 LincolnMA.pdf: 1667449 bytes, checksum: b8113389f31903ba22cf94dbc22192c1 (MD5) Previous issue date: 2009-08-13 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / This work presents a theoretical and numerical analysis of structures using frequency selective surfaces applied on patch antennas. The FDTD method is used to determine the time domain reflected fields. Applications of frequency selective surfaces and patch antennas cover a wide area of telecommunications, especially mobile communications, filters and WB antennas. scattering parameters are obteained from Fourier Transformer of transmited and reflected fields in time domain. The PML are used as absorbing boundary condition, allowing the determination of the fields with a small interference of reflections from discretized limit space. Rectangular patches are considered on dielectric layer and fed by microstrip line. Frequency selective surfaces with periodic and quasi-periodic structures are analyzed on both sides of antenna. A literature review of the use of frequency selective surfaces in patch antennas are also performed. Numerical results are also compared with measured results for return loss of analyzed structures. It is also presented suggestions of continuity to this work / Este trabalho apresenta uma an?lise te?rica e num?rica de estruturas que utilizam superf?cies seletivas de frequ?ncia aplicadas a antenas do tipo patch. Para isso, ? utilizado o m?todo das diferen?as finitas no dom?nio do tempo (FDTD) visando determinar os campos refletidos a partir de uma onda plana incidente no dom?nio do tempo. As aplica??es das superf?cies seletivas de freq??ncia e antenas patch abrangem uma grande ?rea das Telecomunica??es, principalmente em comunica??es m?veis e v?o desde filtros at? as antenas banda larga. Especificamente, a an?lise usa os campos transmitidos e refletidos obtidos no dom?nio do tempo, em conjunto com transformada de Fourier permitindo a obten??o dos par?metros de transmiss?o da antena. A condi??o de contorno absorvedora utilizada foi a de camada perfeitamente casada (PML), permitindo a determina??o num?rica dos campos com uma quantidade menor de interfer?ncias provenientes de reflex?es nos limites do espa?o discretizado. S?o considerados patches retangulares condutores sobre uma camada diel?trica e alimentados por linha de microfita. Foram analisadas superf?cies seletivas de frequ?ncia peri?dicas e quase peri?dicas tanto no plano de terra quanto no plano do pr?prio patch. ? realizada uma revis?o bibliogr?fica a respeito da utiliza??o de superf?cies seletivas de frequ?ncia em antenas patch. Tamb?m s?o comparados resultados num?ricos e medidos para a perda de retorno das estruturas analisadas. S?o apresentadas, ainda, sugest?es de continuidade para este trabalho

Made available in DSpace on 2014-12-17T14:56:06Z (GMT). No. of bitstreams: 1 JoseIAT_DISSERT.pdf: 2877383 bytes, checksum: 0665f7dd94ce1dd4d8883a4f2e5e7832 (MD5) Previous issue date: 2010-12-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work aims to investigate the behavior of fractal elements in planar microstrip structures. In particular, microstrip antennas and frequency selective surfaces (FSSs) had changed its conventional elements to fractal shapes. For microstrip antennas, was used as the radiating element of Minkowski fractal. The feeding method used was microstrip line. Some prototypes were built and the analysis revealed the possibility of miniaturization of structures, besides the multiband behavior, provided by the fractal element. In particular, the Minkowski fractal antenna level 3 was used to exploit the multiband feature, enabling simultaneous operation of two commercial tracks (Wi-Fi and WiMAX) regulated by ANATEL. After, we investigated the effect of switches that have been placed on the at the pre-fractal edges of radiating element. For the FSSs, the fractal used to elements of FSSs was D?rer s pentagon. Some prototypes were built and measured. The results showed a multiband behavior of the structure provided by fractal geometry. Then, a parametric analysis allowed the analysis of the variation of periodicity on the electromagnetic behavior of FSS, and its bandwidth and quality factor. For numerical and experimental characterization of the structures discussed was used, respectively, the commercial software Ansoft DesignerTM and a vector network analyzer, Agilent N5230A model / Este trabalho tem como objetivo investigar o comportamento de elementos fractais em estruturas planares de microfita. Em particular, as antenas de microfita e as superf?cies seletivas de frequ?ncia (FSSs) tiveram seus elementos convencionais alterados para formatos fractais. Para as antenas de microfita, usou-se como elemento radiante o fractal de Minkowski. O m?todo de alimenta??o utilizado nas antenas foi atrav?s de linha de microfita. Alguns prot?tipos foram constru?dos e a an?lise realizada mostrou a possibilidade de miniaturiza??o das estruturas, al?m do comportamento multibanda, proporcionado pelo elemento fractal. Em particular, a antena fractal de Minkowski de n?vel 3 foi utilizada para explorar a caracter?stica multibanda, possibilitando seu funcionamento simult?neo em duas faixas comerciais (Wi-Fi e WiMAX) regulamentadas pela ANATEL. Em seguida, foi investigado o efeito de chaves que foram colocadas nas bordas pr?-fractais do elemento radiante. Para as FSSs, o fractal adotado para atuar como elemento da FSS foi o pent?gono de D?rer. Alguns prot?tipos foram constru?dos e medidos. Os resultados mostraram um comportamento multibanda proporcionado pela geometria fractal. Em seguida, uma an?lise param?trica possibilitou a an?lise da influ?ncia da varia??o da periodicidade no comportamento eletromagn?tico das FSSs, bem como sua largura de banda e seu fator de qualidade. Na caracteriza??o num?rica e experimental das estruturas abordadas, utilizou-se, respectivamente, o software comercial Ansoft DesignerTM e um analisador de redes vetorial, modelo N5230A da Agilent

The manipulation of electromagnetic radiation via the use of periodic arrays of sub-wavelength metallic structures (unit cells), nowadays named "metamaterials", has been known of in the microwave engineering community for over fifty years. In the last decade interest in such sub-wavelength structures grew, mainly due to their ability to interact with radiation in ways natural materials could not e.g. by producing a negative refractive index (NRI). This project sought to see whether NRI metamaterials could provide benefits to the mm and sub-mm wavelength astronomical instrumentation currently in use. To aid rapid design and optimisation of devices made from a cascaded set of metamaterial unit cells, a hybridised Transmission Line (TL) model was developed where the matrix components used in the TL model were "seeded" with data taken from a Finite Element Method (FEM) model of a simpler structure. A comparison between the two found that the TL model was capable of providing results that differed from the FEM model by no more than ~10E−4 for the transmitted intensity, |S21|^2, and <1° for transmitted phase, arg(S21). A slab of material with a refractive index, n = −1, can exhibit an effect known as "superlensing". A three unit cell thick NRI slab was designed, manufactured and experimentally tested. It was found to be capable of producing an NRI across a fractional band of at least 21%, producing a refractive index value of n = −1 at around 90 GHz. The experimental and simulated transmission and reflection data show good match with each other. A highly birefringent air gap Half Wave Plate (HWP) was designed, manufactured and experimentally tested. Defining its useful bandwidth as the region where the phase difference, is equal to (−180 ± 3)° a single HWP had a fractional bandwidth of 0.3%. The bandwidth was extended by using the Pancharatnam method, developed in the 1950's to produce highly achromatic optical wave plates. The method however is applicable to other frequencies and polarisation control technologies. Optimising a three HWP TL-based Pancharatnam model, the HWP's modelled fractional bandwidth increased to 6.6%. Experimental data agrees with the model showing a plateauing of the phase difference at −180°. A highly birefringent polypropylene embedded Quarter Wave Plate (QWP) was also designed, manufactured and tested. Defining its useful bandwidth as the region where the differential phase is (90 ± 2)° a single QWP produced a fractional bandwidth of 0.6%. By optimising a four QWP TL-based Pancharatnam model, the QWP's performance was improved to 7.8%. Experimental data, whilst not in complete agreement with the model does show a reduction in the gradient of phase difference where it crossed 90°. It was found that current designs for NRI metamaterials fall short of the standards required to be used in quasi-optical astronomical instrumentation due to high dispersion and absorption. The high dispersion limits NRI metamaterials to uses in instruments built for narrowband applications. Whilst the Pancharatnam method can increase bandwidths where a flat differential phase response is required, this comes at the cost of increased absorption. To reach their full potential, NRI metamaterials' lossiness must be reduced e.g. possibly by cryogenic means or the use of "active" metamaterials.