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

Made available in DSpace on 2014-12-17T14:56:11Z (GMT). No. of bitstreams: 1 EwinLFB_DISSERT.pdf: 1133428 bytes, checksum: 7db5058d9183e9d7e1e87f596676c111 (MD5) Previous issue date: 2012-07-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The main objective of this work is to optimize the performance of frequency selective surfaces (FSS) composed of crossed dipole conducting patches. The optimization process is performed by determining proper values for the width of the crossed dipoles and for the FSS array periodicity, while the length of the crossed dipoles is kept constant. Particularly, the objective is to determine values that provide wide bandwidth using a search algorithm with representation in bioinspired real numbers. Typically FSS structures composed of patch elements are used for band rejection filtering applications. The FSS structures primarily act like filters depending on the type of element chosen. The region of the electromagnetic spectrum chosen for this study is the one that goes from 7 GHz to 12 GHz, which includes mostly the X-band. This frequency band was chosen to allow the use of two X-band horn antennas, in the FSS measurement setup. The design of the FSS using the developed genetic algorithm allowed increasing the structure bandwidth / Este trabalho tem como objetivo principal efetuar a otimiza??o do desempenho de estruturas de superf?cies seletivas de frequ?ncia FSS (Frequency Selective Surface), com patches condutores na forma de dipolos em cruz. A otimiza??o foi realizada atrav?s da identifica??o de valores ?timos para a largura do dipolo e a periodicidade do arranjo, considerando o valor do comprimento do dipolo fixo. Especificamente, objetiva-se determinar valores que permitam aumentar a largura de banda, utilizando um algoritmo de busca bioinspirado com representa??o em n?meros reais. As aplica??es t?picas de estruturas de FSS com patches condutores utilizam frequ?ncias selecionadas atrav?s das faixas de rejei??o. As estruturas de FSS funcionam basicamente como filtros dependendo do tipo de elemento escolhido. A regi?o do espectro eletromagn?tico escolhida para este estudo foi a faixa de 7 GHz a 12 GHz, que inclui basicamente a banda X. Essa regi?o do espectro eletromagn?tico foi escolhida para possibilitar a medi??o do dispositivo com a utiliza??o de antenas de abertura do tipo corneta, que operam na banda X. O projeto da FSS com a utiliza??o do algoritmo gen?tico GA (Genetic Algorithm) permitiu aumentar a largura de banda da estrutura

Made available in DSpace on 2014-12-17T14:56:20Z (GMT). No. of bitstreams: 1 FranciscoCGSS_Capa_ate_pag41.pdf: 9091246 bytes, checksum: 6f81612f5fd4ab8558666746d9be5489 (MD5) Previous issue date: 2014-06-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Frequency selective surfaces (Frequency Selective Surface - FSS) are often used in various applications in telecommunications. Some of these applications may require that these structures have response with multiple resonance bands. Other applications require that the FSS response have large frequency range, to meet the necessary requirements. FSS to design with these features there are numerous techniques cited in the scientific literature. Thus, the purpose of this paper is to examine some common techniques such as: Overlap of FSS; Elements combined; Elements Elements convolucionados and fractals. And designing multiband FSS and / or broadband selecting simple ways in terms of construction and occupy the smallest possible space, aiming at practical applications. Given these requirements, three projects FSS were performed: a technology applied to IEEE 802.11 a/b/g/n and two projects for application in UWB. In project development, commercial software Ansoft DesignerTM and experimental results were satisfactory was used / Superf?cies seletivas em frequ?ncia (Frequency Selective Surface - FSS) s?o usadas frequentemente em diversas aplica??es em telecomunica??es. Algumas dessas aplica??es podem exigir que essas estruturas tenham resposta com m?ltiplas bandas de resson?ncia. Outras aplica??es exigem que as FSS tenham resposta em faixa larga de frequ?ncia, para atender aos requisitos necess?rios. Para projetar uma FSS com essas caracter?sticas existem in?meras t?cnicas citadas na literatura cient?fica. Assim, o prop?sito deste trabalho ? analisar algumas t?cnicas utilizadas tais como: Sobreposi??o de FSS; Elementos combinados; Elementos convolucionados e Elementos fractais. E projetar FSS multibanda e/ou banda larga selecionando maneiras simples em termos de constru??o e que ocupem o menor espa?o poss?vel, visando aplica??es pr?ticas. Tendo em vista estes requisitos, foram realizados tr?s projetos de FSS: um aplicado a tecnologia IEEE 802.11 a/b/g/n e dois projetos para aplica??o em UWB. No desenvolvimento dos projetos, foi utilizado o software comercial Ansoft DesignerTM e os resultados experimentais se mostraram satisfat?rios

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-01-23T14:13:10Z No. of bitstreams: 1 PhelipeSenaOliveira_TESE.pdf: 2369727 bytes, checksum: 2bb1dad07260b4efd645c7028636e62f (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-01-24T15:05:44Z (GMT) No. of bitstreams: 1 PhelipeSenaOliveira_TESE.pdf: 2369727 bytes, checksum: 2bb1dad07260b4efd645c7028636e62f (MD5) / Made available in DSpace on 2018-01-24T15:05:44Z (GMT). No. of bitstreams: 1 PhelipeSenaOliveira_TESE.pdf: 2369727 bytes, checksum: 2bb1dad07260b4efd645c7028636e62f (MD5) Previous issue date: 2017-02-06 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / As novas configura??es de dispositivos e circuitos de micro-ondas resulta em aumento de complexidade nos processos de desenvolvimento, particularmente nos casos de s?ntese. Antenas e superf?cies seletivas de frequ?ncia (Frequency Selective Surface - FSS) s?o estruturas muito importantes nos sistemas de comunica??es, que podem ser otimizadas pela atua??o dos algoritmos bioinspirados. Geralmente, para que os algoritmos bioinspirados auxiliem na otimiza??o dessas estruturas ? necess?ria a implementa??o de t?cnicas de an?lise num?rica como o M?todo dos Momentos ou Elementos Finitos. Diante da dificuldade de modelagem das t?cnicas descritas, ? comum a utiliza??o de uma fun??o de estima??o, como as Redes Neurais Artificiais, para substituir a an?lise num?rica. Embora encontre solu??es desejadas, as estima??es s?o realizadas ap?s um processo de treinamento efetuado atrav?s de uma base de dados. Cada estrutura de antena ou FSS exige uma base de dados espec?fica. Este trabalho prop?e uma t?cnica de otimiza??o baseado na utiliza??o de um algoritmo bioinspirado e um framework que realiza a integra??o do algoritmo ao software comercial ANSYS HFSS. O prop?sito ? realizar as simula??es das poss?veis solu??es durante a execu??o do algoritmo bioinspirado, e com isso, evitar o uso de uma base de dados, e assim, tornar a t?cnica eficiente e flex?vel com rela??o ?s altera??es nas estruturas de antenas ou FSS. Outro objetivo original deste trabalho ? a utiliza??o do algoritmo Social Spider Optimization ? SSO para a solu??o de problemas na ?rea de eletromagnetismo aplicado. Para comprovar a efic?cia da t?cnica proposta alguns projetos de antena e FSS s?o otimizados atrav?s de varia??es em seus par?metros estruturais. Os resultados obtidos na otimiza??o dos projetos dos circuitos s?o comparados com outras t?cnicas, tendo sido observado uma boa concord?ncia. / The new settings for devices and microwaves circuits result in an increase of complexity in the processes of development, specially in regards to the process of synthesis. Antennas and Frequency Selective Surfaces (FSS) are primordial in communication systems. Alternatively, these structures may be optimized through the usage of bio-inspired algorithms. Generally, in order for the bio-inspired algorithms to assist in the optimization of FSS structures, it is necessary to implement several numerical analysis techniques, such as the method of moments or finite elements. Because of the difficulty to model such methods, it has been turned common the usage of a point estimation function, such as artificial neural networks, to substitute the numerical analysis. Although these procedures end up encountering desirable solutions, the estimations are done after a training process conducted through a database. Additionally, every FSS antenna demands a specific database. This work proposes an optimization technique that relies on the usage of a bio-inspired algorithm and a framework (that provides the integration between the algorithm and the commercial software ANSS HFSS). The purpose of the work is to do simulations of possible solutions during the execution of the bio-inspired algorithm; therefore, avoiding the usage of the database; and so, make the technique flexible and efficient in relation to altering the antennas? structures or FSS. Furthermore, another objective of this work is the usage of the algorithm, namely Social Spider Optimization - SSO in the search for solutions in the field of applied electromagnetism. In order to prove the efficiency of the proposed techniques, some FSS? and antennas? projects are optimized through the variation of their structural parameters. In conclusion, the results that were obtained through the procedures previously shown, are compared to other techniques, resulting in a satisfying agreement rate.

Over the past two decades the mobile wireless communication systems has been growing fast and continuously. Therefore, the standardization bodies together with wireless researchers and mobile operators around the globe have been constantly working on new technical specifications in order to meet the demand for this rapid growth. The 3rd Generation Partnership Project (3GPP) one of the largest of such standardization bodies, works on developing the current third generation (3G) mobile telecommunication systems towards the future 4th generation. Research towards meeting the higher demands for higher data rates was the main reason for the birth of an evolution technology towards the 4th generation mobile systems. This evolution to the current 3rd generation UMTS systems was given the name E-UTRA/UTRAN Long Term Evolution (LTE) by the 3GPP. This thesis research has been carried out at the Telecommunications Research Center (ftw.) in Vienna. It was conducted in the framework of the C10 project “Wireless Evolution Beyond 3G”. One of the fields of research within this project is to have a special focus on the OFDM modulation schemes that are discussed under the new evolution technology (LTE) of the UMTS mobile networks. Therefore, this thesis focuses mainly in analyzing the new requirements, and evaluating them by designing a low-complexity UMTS-LTE OFDM based transceiver. This thesis aims mainly in studying the feasibility of this technology by means of simulation. / Tel: +46-704469795 Email: osman@ftw.at,amos04@student.bth.se, ammarmao@gmail.com

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.

Metoda koneÄnch prvk implementovan v programu COMSOL Multiphysics je vyu­vna k analze tzv. free-standing kmitoÄtovÄ selektivn­ch povrch ve 3D. Tyto modely jsou nslednÄ doplnÄny o periodick© okrajov© podm­nky. Dle jsou free-standing povrchy doplnÄny o vrstvy dielektrika a je zkoumn jejich vliv na modul Äinitele odrazu. V analytick© Ästi jsou vyhodnoceny vlivy poÄtu element diskretizaÄn­ m­ky na pesnost vsledku a d©lku vpoÄt. Vsledky jsou srovnvny vzhledem k vsledkm uvedenm v literatue [5]. V zvÄreÄn© Ästi prce je vysvÄtlen postup pi generovn­ m-file pro obd©ln­kov element a pouit­ globln­ho optimalizaÄn­ho algoritmu PSO, kter automaticky upravuje rozmÄry vodiv©ho motivu tak, aby bylo dosaeno prbÄhu modulu Äinitele odrazu podle poadovan©ho prbÄhu.

This dissertation explores the role of polarization, combining, and equalization operating over frequency-selective channels to improve the reliability of wireless communications systems in terms of BER for two applications: 5G mobile networks (operating in the mmWave band and NR FR1), and aeronautical mobile telemetry systems (operating in L band). The equivalent discrete-time models for a variety of spatial combining techniques at 5G mmWave bands were derived to investigate the performance of co-located cross-polarized antenna elements when polarization diversity is used and also when a combination of spatial and cross-polarized antennas is exploited. In both cases, ML combining has the lowest BER and EPC produced the worst results. The use of co-located cross-polarized antenna elements also is examined in 5G FR1 assuming post-FFT processing of the two antenna element outputs in a mobile-to-mobile setting. The optimum strategy, in the ML sense, for incorporating the two antenna outputs is developed. The optimum combining strategy together with a FDE is compared to the traditional combining techniques: MRC, EGC, and SC, where the last two also require a FDE. Computer simulations performed over a stochastic channel model with polarization state information show that the difference between ML detection and MRC (the best performing methods) and SC with FDE (the worst performing method) is 2 dB. The similar results were observed with pilot based channel estimators, however the difference in this case was the presence of a BER floor at low values of $N_0$ and caused by channel estimation errors. In aeronautical mobile telemetry applications, the ML combiner is derived and shown to be equivalent to the summing the outputs of two filters matched to the channels in the horizontal and vertical polarization states. For historical reasons, current systems combine right-hand and left-hand circularly polarized antenna feed outputs using a MRC. To compare the two combining approaches, the aeronautical telemetry multipath channel was extended to include polarization state information. The simulation results for SOQPSK-TG with a CMA equalizer show that the post-equalizer BER for the two approaches is the same.

No description available.