Submitted by Alex Sandro R?go (alex@ifpb.edu.br) on 2016-12-06T12:54:11Z No. of bitstreams: 1 13- Leidiane Carolina Martins de Moura - CARACTERIZA??O DE FSS COM GEOMETRIA ESTRELA DE QUATRO BRA?OS TIPO FENDA.pdf: 4635689 bytes, checksum: 77bcdf0d2afb1698001014e0f84d5367 (MD5) / Approved for entry into archive by Alex Sandro R?go (alex@ifpb.edu.br) on 2016-12-06T12:56:04Z (GMT) No. of bitstreams: 1 13- Leidiane Carolina Martins de Moura - CARACTERIZA??O DE FSS COM GEOMETRIA ESTRELA DE QUATRO BRA?OS TIPO FENDA.pdf: 4635689 bytes, checksum: 77bcdf0d2afb1698001014e0f84d5367 (MD5) / Made available in DSpace on 2016-12-06T12:56:04Z (GMT). No. of bitstreams: 1 13- Leidiane Carolina Martins de Moura - CARACTERIZA??O DE FSS COM GEOMETRIA ESTRELA DE QUATRO BRA?OS TIPO FENDA.pdf: 4635689 bytes, checksum: 77bcdf0d2afb1698001014e0f84d5367 (MD5) Previous issue date: 2016-12-06 / Nos ?ltimos anos, devido ao intenso crescimento de aplica??es que utilizam os sistemas de telecomunica??es, a demanda de disponibilidade de bandas de frequ?ncia do espectro eletromagn?tico tem se tornado cada vez maior. Embora esse crescimento seja determinado principalmente por tecnologias desenvolvidas para tablets e smartphones, o espectro eletromagn?tico ? ainda disputado por diversos servi?os, tais como os sistemas de posicionamento global, TV digital, servi?os de internet e outros. Diante disso, os engenheiros de telecomunica??es e micro-ondas buscam por novas tecnologias capazes de suprir as demandas espec?ficas desses dispositivos. Nesse contexto, uma das estruturas que tem recebido consider?vel aten??o de diversos grupos de pesquisa ? a superf?cie seletiva em frequ?ncia, FSS, pois pode desempenhar um papel fundamental na otimiza??o de sistemas de telecomunica??es, possibilitando, entre outras aplica??es, a redu??o de sinais indesej?veis e opera??o multibanda. A fim de se obter dimens?es reduzidas, resposta em frequ?ncia espec?fica e opera??o multibanda, diversas geometrias s?o estudadas, incluindo elementos simples ou uma combina??o dos mesmos, em que o elemento da c?lula unit?ria pode ser constitu?do a partir de uma camada de metaliza??o impressa sobre um substrato diel?trico, ou uma fenda em uma camada de metaliza??o sobre um substrato diel?trico. Logo, neste trabalho ? presentada a an?lise da geometria estrela de quatro bra?os tipo fenda para FSS, destacandose as suas caracter?sticas de redu??o de dimens?es e opera??o multibanda. O dimensionamento da estrutura, o ajuste da resposta em frequ?ncia e a sua reconfigura??o a partir da comuta??o s?o aspectos abordados. Para a an?lise num?rica das FSS s?o utilizados o M?todo das Ondas, mais conhecido na literatura como WCIP (Wave Concept Iterative Procedure), empregando o programa WCIPAG08?, desenvolvido no GTEMA-IFPB, e o M?todo dos Momentos, no qual se baseia o programa comercial ANSOFT-DESIGNER. Os resultados num?ricos e experimentais apresentaram boa concord?ncia entre si. Al?m disso, observa-se que o ajuste da resposta em frequ?ncia e a opera??o multibanda foram obtidos sem altera??o das dimens?es da c?lula unit?ria. S?o propostas equa??es aproximadas de projetos e apresentada a compara??o entre as caracteriza??es anal?tica, num?rica e experimental.

Submitted by Programa de P?s-Gradua??o Engenharia El?trica (ppgee@ifpb.edu.br) on 2018-04-17T14:19:19Z No. of bitstreams: 1 25- Jo?o Batista de Oliveira Silva - DESENVOLVIMENTO DE SUPERF?CIES SELETIVAS EM FREQU?NCIA COM BANDA DUPLA DE OPERA??O BASEADAS NA GEOMETRIA ESTRELA DE QUATRO BRA?OS ASSOCIADA A AN?IS TRAPEZOIDAIS.pdf: 2567327 bytes, checksum: 4ae3238070d40c3a7a850b03643aa35a (MD5) / Approved for entry into archive by Programa de P?s-Gradua??o Engenharia El?trica (ppgee@ifpb.edu.br) on 2018-04-17T14:23:44Z (GMT) No. of bitstreams: 1 25- Jo?o Batista de Oliveira Silva - DESENVOLVIMENTO DE SUPERF?CIES SELETIVAS EM FREQU?NCIA COM BANDA DUPLA DE OPERA??O BASEADAS NA GEOMETRIA ESTRELA DE QUATRO BRA?OS ASSOCIADA A AN?IS TRAPEZOIDAIS.pdf: 2567327 bytes, checksum: 4ae3238070d40c3a7a850b03643aa35a (MD5) / Made available in DSpace on 2018-04-17T14:23:44Z (GMT). No. of bitstreams: 1 25- Jo?o Batista de Oliveira Silva - DESENVOLVIMENTO DE SUPERF?CIES SELETIVAS EM FREQU?NCIA COM BANDA DUPLA DE OPERA??O BASEADAS NA GEOMETRIA ESTRELA DE QUATRO BRA?OS ASSOCIADA A AN?IS TRAPEZOIDAIS.pdf: 2567327 bytes, checksum: 4ae3238070d40c3a7a850b03643aa35a (MD5) Previous issue date: 2016-11-07 / A principal finalidade das telecomunica??es ? suprir a necessidade humana de se comunicar ? dist?ncia. Ultimamente, devido ao intenso crescimento de aplica??es que utilizam os sistemas de telecomunica??es, a demanda de disponibilidade de bandas de frequ?ncia do espectro eletromagn?tico tem se tornado cada vez maior, gerando necessidades de novas tecnologias para suprir estes requisitos espec?ficos tanto de resposta em frequ?ncia, como n?veis de pot?ncia. Neste contexto, as FSS v?m recebendo a aten??o de diversos grupos de pesquisa, pois podem desempenhar um papel fundamental na otimiza??o de circuitos e antenas. Neste trabalho, ? proposto o desenvolvimento de superf?cies seletivas em frequ?ncia com banda dupla de opera??o, baseadas na geometria, estrela de quatro bra?os associada a an?is trapezoidais. Inicialmente, as caracter?sticas de cada geometria s?o analisadas separadamente. Em seguida, discute-se o efeito da associa??o das duas geometrias. S?o propostas as equa??es iniciais de projeto e apresentados os resultados num?ricos, obtidos com a simula??o com o software Ansys Designer?, sendo esses comparados com resultados experimentais, observando-se uma boa concord?ncia entre os mesmos. Como exemplo de potencial aplica??o, uma frequ?ncia de resson?ncia indesejada ? deslocada e uma FSS com banda dupla de opera??o ? obtida. Considerando as caracter?sticas observadas, assim como a flexibilidade no ajuste da resposta em frequ?ncia, a geometria proposta ?, potencialmente, atrativa para aplica??es tais como FSS reconfigur?veis e paredes inteligentes.

Submitted by Programa de P?s-Gradua??o Engenharia El?trica (ppgee@ifpb.edu.br) on 2018-04-17T17:01:34Z No. of bitstreams: 1 45- Juliete da Silva Souza - AN?LISE DE SUPERF?CIE SELETIVA EM FREQU?NCIA BASEADA NA GEOMETRIA AN?IS TRAPEZOIDAIS ABERTOS.pdf: 3638660 bytes, checksum: 68ead463fe94dc7fe1c447f2ff2a66af (MD5) / Approved for entry into archive by Programa de P?s-Gradua??o Engenharia El?trica (ppgee@ifpb.edu.br) on 2018-04-17T17:02:41Z (GMT) No. of bitstreams: 1 45- Juliete da Silva Souza - AN?LISE DE SUPERF?CIE SELETIVA EM FREQU?NCIA BASEADA NA GEOMETRIA AN?IS TRAPEZOIDAIS ABERTOS.pdf: 3638660 bytes, checksum: 68ead463fe94dc7fe1c447f2ff2a66af (MD5) / Made available in DSpace on 2018-04-17T17:02:41Z (GMT). No. of bitstreams: 1 45- Juliete da Silva Souza - AN?LISE DE SUPERF?CIE SELETIVA EM FREQU?NCIA BASEADA NA GEOMETRIA AN?IS TRAPEZOIDAIS ABERTOS.pdf: 3638660 bytes, checksum: 68ead463fe94dc7fe1c447f2ff2a66af (MD5) Previous issue date: 2018-04-04 / PRPIPG / Os servi?os de comunica??es m?veis t?m crescido consideravelmente nos ?ltimos anos, e as aplica??es voltadas para smartphones e tablets (TV digital, geolocaliza??o, servi?os de internet, entre outros) est?o se tornando cada vez mais populares. Al?m dessas aplica??es para drones (ve?culo n?o tripulados) tamb?m v?m se popularizando. Tais servi?os, demandam redes de alta capacidade, com requisitos espec?ficos de opera??o, como faixa de frequ?ncia e n?veis de pot?ncia. ? neste contexto que as superf?cies seletivas em frequ?ncia, FSS (do ingl?s Frequency Selective Surfaces) t?m se destacado em diversas aplica??es na ?rea de telecomunica??es. Essas estruturas apresentam uma resposta em frequ?ncia dependente da geometria da c?lula unit?ria, do tipo de elemento, das caracter?sticas do diel?trico (como por exemplo, a constante diel?trica, altura e a tangente de perdas), da periocidade do arranjo e da polariza??o da onda incidente. No GTEMA-IFPB (Grupo de Telecomunica??es e Eletromagnetismo Aplicado do IFPB) t?m sido realizados estudos voltados ao desenvolvimento de novas geometrias para o elemento b?sico da FSS, dentre os quais podem ser citados: estrela de quatro bra?os, matrioska, geometria em forma de U, an?is trapezoidais, entre outros. Dando prosseguimento aos estudos de novas geometrias para c?lulas unit?rias de FSS realizados pelo GTEMA?IFPB, este trabalho tem como objetivo verificar o funcionamento e estabelecer as regras de projetos para uma FSS baseada na geometria an?is trapezoidais abertos. S?o propostas as equa??es iniciais de projeto e apresentados os resultados num?ricos, obtidos por meio de simula??o utilizando o software ANSYS Designer, sendo esses comparados com resultados experimentais, observando-se uma boa concord?ncia entre os mesmos. A geometria proposta ? flex?vel no ajuste da resposta em frequ?ncias devido a excita??o dos an?is em pares, o que permite o ajuste, de forma quase independente, das respectivas frequ?ncias de resson?ncia, sendo potencialmente atrativa para aplica??es com FSS reconfigur?veis e paredes inteligentes.

The last seven hot rolling passes of the ferritic stainless steels (FSS) AISI 430 and AISI 433 (the latter an Al-added variant of 430) were simulated on Gleeble-1500D® and Gleeble-3800TM® thermo-mechanical simulators to investigate the effect of temperature, strain rate and inter-pass time on the development of texture in these steel grades and its subsequent influence on ridging. The compression tests were carried out over a wide range of strain rates (0.1 s-1 to 5 s-1, 25 s-1 and 50 s-1) and temperatures (1100 to 820 oC) with different inter-pass times (2 s, 10 s, 20 s and 30 s). The transition temperature from dynamic recrystallization (which may introduce a texture change) to dynamic recovery (in which no texture changes are expected) was determined by examining the relationship between the mean flow stress and the deformation temperature in multi-pass tests. Both macrotexture (XRD) and microtexture (EBSD) analyses were employed to characterise and study the texture present in these steels. It was found that the texture in the central layer of the compressed sample is a strong recrystallization-type. The through-thickness textural and microstructural banding was found to be responsible for ridging in these grades of stainless steels. Dynamic recrystallization which promotes the formation of the desired ã-fibre texture leading to high ductility, formability and eventually reduction or elimination of ridging, was found to occur in both AISI 430 and AISI 433 at high temperatures, low strain rates and longer inter-pass times with multi-pass testing. Generally AISI 433 has a stronger gamma texture developed than the AISI 430 when hot rolled under similar conditions, which leads to improved ductility and less ridging in AISI 433 than AISI 430. / Dissertation (MSc)--University of Pretoria, 2012. / Materials Science and Metallurgical Engineering / unrestricted

No description available.

Yes / In this article, a novel uniplanar ultra‐wideband (UWB) stop frequency selective surface (FSS) was miniaturized to maximize the gain of a compact UWB monopole antenna for microwave imaging applications. The single‐plane FSS unit cell size was only 0.095λ × 0.095λ for a lower‐operating frequency had been introduced, which was miniaturized by combining a square‐loop with a cross‐dipole on FR4 substrate. The proposed hexagonal antenna was printed on FR4 substrate with coplanar waveguide feed, which was further backed at 21.6 mm by 3 × 3 FSS array. The unit cell was modeled with an equivalent circuit, while the measured characteristics of fabricated FSS array and the antenna prototypes were validated with the simulation outcomes. The FSS displayed transmission magnitude below −10 dB and linear reflection phase over the bandwidth of 2.6 to 11.1 GHz. The proposed antenna prototype achieved excellent gain improvement about 3.5 dBi, unidirectional radiation, and bandwidth of 3.8 to 10.6 GHz. Exceptional agreements were observed between the simulation and the measured outcomes. Hence, a new UWB baggage scanner system was developed to assess the short distance imaging of simulated small metallic objects in handbag model. The system based on the proposed antenna displayed a higher resolution image than the antenna without FSS.

Yes / A Novel design of a curved single-layered frequency selective surface with an 11 × 11 array of a 13 × 13 mm-sized unit cell has been merged with a miniaturized, CPW-fed ultra-wideband monopole of dimensions (20 × 25 mm2) for gain enhancement. The suggested prototype, crafted on an FR-4 dielectric substrate and demonstrates a very broad bandwidth starting from 2.66 to 17.98 GHz (148%), which covers the entire UWB frequency band. The combined antenna-curved FSS reflector shows a very important gain improvement from 0.2–5.4 dB to 8.8–14.9 dB, having a peak gain increase of 10 dB at 10.6 GHz. Basic design features were studied and discussed through simulations, yielding promising results The proposed structure can be used in UWB and GPR applications.

Les structures planaires de grandes tailles sont de plus en plus utilisées dans les applications des satellites et des radars. Deux grands types de ces structures à savoir les FSS et les Reflectarrays sont particulièrement les plus intéressants dans les domaines de la conception RF. Mais en raison de leur grande taille et de la complexité des cellules élémentaires, l‘analyse complète de ces structures nécessite énormément de mémoire et des temps de calcul excessif. Par conséquent, les techniques classiques basées sur maillage linéaire soit ne parviennent pas à simuler de telles structures soit, exiger des ressources non disponibles à un concepteur d'antenne. Une technique appelée « technique par changement d'échelle » tente de résoudre ce problème par partitionnement de la géométrie du réseau par de nombreux domaines imbriqués définis à différents niveaux d'échelle du réseau. Le multi-pôle par changement d'échelle, appelé « Scale changing Network (SCN) », modélise le couplage électromagnétique entre deux échelles successives, en résolvant une formulation intégral des équations de Maxwell par une technique basée sur la méthode des moments. La cascade de ces multi-pôles par changement d'échelle, permet le calcul de la matrice d'impédance de surface de la structure complète qui peut à son tour être utilisées pour calculer la diffraction en champ lointain. Comme le calcul des multi-pôles par changement d'échelle est mutuellement indépendant, les temps d'exécution peuvent être réduits de manière significative en parallélisant le calcul. Par ailleurs, la modification de la géométrie de la structure à une échelle donnée nécessite seulement le calcul de deux multi-pôles par changement d'échelle et ne requiert pas la simulation de toute la structure. Cette caractéristique fait de la SCT un outil de conception et d'optimisation très puissant. Des structures planaires uniformes et non uniformes excité par un cornet ont étés modélisés avec succès, avec des temps de calcul délais intéressants, employant les ressources normales de l'ordinateur. / Large sized planar structures are increasingly being employed in satellite and radar applications. Two major kinds of such structures i.e. FSS and Reflectarrays are particularly the hottest domains of RF design. But due to their large electrical size and complex cellular patterns, full-wave analysis of these structures require enormous amount of memory and processing requirements. Therefore conventional techniques based on linear meshing either fail to simulate such structures or require resources not available to a common antenna designer. An indigenous technique called Scale-changing Technique addresses this problem by partitioning the cellular array geometry in numerous nested domains defined at different scale-levels in the array plane. Multi-modal networks, called Scale-changing Networks (SCN), are then computed to model the electromagnetic interaction between any two successive partitions by Method of Moments based integral equation technique. The cascade of these networks allows the computation of the equivalent surface impedance matrix of the complete array which in turn can be utilized to compute far-field scattering patterns. Since the computation of scale-changing networks is mutually independent, execution times can be reduced significantly by using multiple processing units. Moreover any single change in the cellular geometry would require the recalculation of only two SCNs and not the entire structure. This feature makes the SCT a very powerful design and optimization tool. Full-wave analysis of both uniform and nonuniform planar structures has successfully been performed under horn antenna excitation in reasonable amount of time employing normal PC resources.

Les structures planaires de tailles finies sont de plus en plus utilisées dans les applications des satellites et des radars. Deux grands types de ces structures sont les plus utilisés dans le domaine de la conception RF à savoir Les Surfaces Sélectives en Fréquence (FSS) et les Reflectarrays. Les FSSs sont un élément clé dans la conception de systèmes multifréquences. Elles sont utilisées comme filtre en fréquence, et trouvent des applications telles que les radômes, les réflecteurs pour antenne Cassegrain, etc. Les performances des FSSs sont généralement évaluées en faisant l'hypothèse d'une FSS de dimension infinie et périodique en utilisant les modes de Floquet, le temps de calcul étant alors réduit quasiment à celui de la cellule élémentaire. Plusieurs méthodes permettant la prise en compte de la taille finie des FSSs ont été développées. La méthode de Galerkin basée sur l'approche rigoureuse permet la prise en compte des interactions entre les différents éléments du réseau, mais cette technique ne fonctionne que pour les FSSs de petite taille, typiquement 3x3 éléments. Pour les grands réseaux, cette méthode n'est plus adaptée, car le temps de calcul et l'exigence en mémoire deviennent trop grands. Donc, une autre approche est utilisée, celle basée sur la décomposition spectrale en onde plane. Elle permet de considérer un réseau fini comme un réseau périodique infini, illuminé partiellement par une onde plane. Avec cette approche, des FSSs de grande taille sont simulées, mais elle ne permet pas dans la plupart des cas, de prendre en compte les couplages qui existent entre les différentes cellules du réseau, les effets de bord non plus. La simulation des FSSs par les méthodes numériques classiques basées sur une discrétisation spatiale (méthode des éléments finis, méthode des différences finies, méthode des moments) ou spectrale (méthodes modales) aboutit souvent à des matrices mal conditionnées, des problèmes de convergence numérique et/ou des temps de calcul excessifs. Pour éviter tous ces problèmes, une technique appelée technique par changements d'échelle tente de résoudre ces problèmes. Elle est basée sur le partitionnement de la géométrie du réseau en plusieurs sous-domaines imbriqués, définis à différents niveaux d'échelle du réseau. Le multi-pôle de changement d'échelle, appelé Scale-Changing Networks (SCN), modélise le couplage électromagnétique entre deux échelles successives. La cascade de ces multi-pôles de changement d'échelle, permet le calcul de la matrice d'impédance de surface de la structure complète et donc la modélisation globale du réseau. Ceci conduit à une réduction significative en termes de temps de calcul et d'espace mémoire par rapport aux méthodes numériques classiques. Comme le calcul des multi-pôles de changement d'échelle est mutuellement indépendant, les temps d'exécution peuvent encore être réduits de manière significative en parallélisant le calcul. La SCT permet donc de modéliser des FSSs Finies tout en prenant en compte le couplage entre les éléments adjacents du réseau. / The finite size planar structures are increasingly used in applications of satellite and radar. Two major types of these structures are the most used in the field of RF design ie Frequency Selective Surfaces (FSS) and the Reflectarrays. The FSSs are a key element in the design of multifrequency systems. They are used as frequency filter, and find applications such as radomes, reflector Cassegrain antenna, etc.. The performances of FSSs are generally evaluated by assuming an infinite dimensional FSS using periodic Floquet modes, the computation time is then reduced almost to that of the elementary cell. Several methods have been developed for taking into account the finite dimensions of arrays. For example the Galerkin method uses a rigorous element by element approach. With this method, the exact interactions between the elements are taken into account but this technique works only for small FSS, typically 3x3 elements. For larger surfaces, this method is no more adapted. The computation time and the memory requirement become too large. So another approach is used based on plane wave spectral decomposition. It allows considering the finite problem as a periodic infinite one locally illuminated. With this approach, large FSS are indeed simulated, but the exact interactions between the elements are not taken into account, the edge effects either. The simulation of FSS by conventional numerical methods based on spatial meshing (finite element method, finite difference, method of moments) or spectral (modal methods) often leads in the practice to poorly conditioned matrices, numerical convergence problems or/and excessive computation time. To avoid these problems, a new technique called Scale Changing Technique attempts to solve these problems. The SCT is based on the partition of discontinuity planes in multiple planar sub-domains of various scale levels. In each sub- omain the higher-order modes are used for the accurate representation of the electromagnetic field local variations while low-order modes are used for coupling the various scale levels. The electromagnetic coupling between scales is modelled by a Scale Changing Network (SCN). As the calculation of SCN is mutually independent, the execution time can still be significantly reduced by parallelizing the computation. With the SCT, we can simulate large finite FSS, taking into account the exact interactions between elements, while addressing the problem of excessive computation time and memory

Made available in DSpace on 2014-12-17T14:55:06Z (GMT). No. of bitstreams: 1 HertzWCL_TESE.pdf: 4465162 bytes, checksum: b8574ba7e4819cb59386ad0ba99ebd86 (MD5) Previous issue date: 2012-10-11 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The frequency selective surfaces, or FSS (Frequency Selective Surfaces), are structures consisting of periodic arrays of conductive elements, called patches, which are usually very thin and they are printed on dielectric layers, or by openings perforated on very thin metallic surfaces, for applications in bands of microwave and millimeter waves. These structures are often used in aircraft, missiles, satellites, radomes, antennae reflector, high gain antennas and microwave ovens, for example. The use of these structures has as main objective filter frequency bands that can be broadcast or rejection, depending on the specificity of the required application. In turn, the modern communication systems such as GSM (Global System for Mobile Communications), RFID (Radio Frequency Identification), Bluetooth, Wi-Fi and WiMAX, whose services are highly demanded by society, have required the development of antennas having, as its main features, and low cost profile, and reduced dimensions and weight. In this context, the microstrip antenna is presented as an excellent choice for communications systems today, because (in addition to meeting the requirements mentioned intrinsically) planar structures are easy to manufacture and integration with other components in microwave circuits. Consequently, the analysis and synthesis of these devices mainly, due to the high possibility of shapes, size and frequency of its elements has been carried out by full-wave models, such as the finite element method, the method of moments and finite difference time domain. However, these methods require an accurate despite great computational effort. In this context, computational intelligence (CI) has been used successfully in the design and optimization of microwave planar structures, as an auxiliary tool and very appropriate, given the complexity of the geometry of the antennas and the FSS considered. The computational intelligence is inspired by natural phenomena such as learning, perception and decision, using techniques such as artificial neural networks, fuzzy logic, fractal geometry and evolutionary computation. This work makes a study of application of computational intelligence using meta-heuristics such as genetic algorithms and swarm intelligence optimization of antennas and frequency selective surfaces. Genetic algorithms are computational search methods based on the theory of natural selection proposed by Darwin and genetics used to solve complex problems, eg, problems where the search space grows with the size of the problem. The particle swarm optimization characteristics including the use of intelligence collectively being applied to optimization problems in many areas of research. The main objective of this work is the use of computational intelligence, the analysis and synthesis of antennas and FSS. We considered the structures of a microstrip planar monopole, ring type, and a cross-dipole FSS. We developed algorithms and optimization results obtained for optimized geometries of antennas and FSS considered. To validate results were designed, constructed and measured several prototypes. The measured results showed excellent agreement with the simulated. Moreover, the results obtained in this study were compared to those simulated using a commercial software has been also observed an excellent agreement. Specifically, the efficiency of techniques used were CI evidenced by simulated and measured, aiming at optimizing the bandwidth of an antenna for wideband operation or UWB (Ultra Wideband), using a genetic algorithm and optimizing the bandwidth, by specifying the length of the air gap between two frequency selective surfaces, using an optimization algorithm particle swarm / As superf?cies seletivas de freq??ncia, ou FSS (Frequency Selective Surfaces), s?o estruturas constitu?das por arranjos peri?dicos de elementos condutores, denominados patches, geralmente muito finos e impressos sobre camadas diel?tricas, ou de aberturas, perfuradas em superf?cies met?licas muito finas, para aplica??es nas faixas de microondas e ondas milim?tricas. Estas estruturas s?o frequentemente utilizadas em aeronaves, m?sseis, sat?lites, radomes, antenas de refletor, antenas de alto ganho e fornos de microondas, por exemplo. A utiliza??o destas estruturas tem como objetivo principal filtrar bandas de freq??ncia, que podem ser de transmiss?o ou de rejei??o, dependendo da especificidade da aplica??o desejada. Por sua vez, os sistemas de comunica??o modernos, tais como GSM (Global System for Mobile Communications), RFID (Radio Frequency Identification), Bluetooth, Wi-Fi e WiMAX, cujos servi?os s?o altamente demandados pela sociedade, t?m requerido o desenvolvimento de antenas que apresentem, como caracter?sticas principais, baixo custo e perfil, al?m de peso e dimens?es reduzidas. Neste contexto, a antena de microfita se apresenta como uma excelente op??o para os sistemas de comunica??es atuais, pois (al?m de atenderem intrinsicamente aos requisitos mencionados) s?o estruturas planares de f?cil fabrica??o e integra??o com outros componentes de circuitos de microondas. Em consequ?ncia, a an?lise e principalmente a s?ntese destes dispositivos, em face da grande possibilidade de formas, dimens?es e periodicidade de seus elementos, tem sido efetuada atrav?s de modelos de onda completa, tais como o m?todo dos elementos finitos, o m?todo dos momentos e o m?todo das diferen?as finitas no dom?nio do tempo. Entretanto, estes m?todos apesar de precisos requerem um grande esfor?o computacional. Neste contexto, a intelig?ncia computacional (IC) tem sido utilizada com sucesso nos projetos e na otimiza??o de estruturas planares de microondas, como uma ferramenta auxiliar e muito adequada, dada a complexidade das geometrias das antenas e das FSS consideradas. A intelig?ncia computacional ? inspirada em fen?menos naturais como: aprendizado, percep??o e decis?o, utilizando t?cnicas como redes neurais artificiais, l?gica fuzzy, geometria fractal e computa??o evolucion?ria. Este trabalho realiza um estudo de aplica??o de intelig?ncia computacional utilizando metaheur?sticas como algoritmos gen?ticos e intelig?ncia de enxames na otimiza??o de antenas e superf?cies seletivas de frequ?ncia. Os algoritmos gen?ticos s?o m?todos computacionais de busca baseados na teoria da sele??o natural proposta por Darwin e na gen?tica utilizados para resolver problemas complexos como, por exemplo, problemas em que o espa?o de busca cresce com as dimens?es do problema. A otimiza??o por enxame de part?culas tem como caracter?sticas a utiliza??o da intelig?ncia de forma coletiva sendo aplicada em problemas de otimiza??o em diversas ?reas de pesquisa. O objetivo principal deste trabalho consiste na utiliza??o da intelig?ncia computacional, na an?lise e s?ntese de antenas e de FSS. Foram consideradas as estruturas de um monopolo planar de microfita, do tipo anel, e de uma FSS de dipolos em cruz. Foram desenvolvidos os algoritmos de otimiza??o e obtidos resultados para as geometrias otimizadas de antenas e FSS consideradas. Para a valida??o de resultados foram projetados, constru?dos e medidos v?rios prot?tipos. Os resultados medidos apresentaram excelente concord?ncia com os simulados. Al?m disso, os resultados obtidos neste trabalho foram comparados com os simulados atrav?s de um software comercial, tendo sido observada tamb?m uma excelente concord?ncia. Especificamente, a efici?ncia das t?cnicas de IC utilizadas foram comprovadas atrav?s de resultados simulados e medidos, objetivando a otimiza??o da largura de banda de uma antena para opera??o em banda ultralarga, ou UWB (Ultra Wideband), com a utiliza??o de um algoritmo gen?tico e da otimiza??o da largura de banda, atrav?s da especifica??o do comprimento do gap de ar entre duas superf?cies seletivas de frequ?ncia, utilizando um algoritmo de otimiza??o por enxame de part?culas