Antennas Array
Mostrando 13-24 de 34 artigos, teses e dissertações.
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13. Study of backfire antennas
The study presented in this article is dedicated to the backfire disk-on-rod antennas fed by a dipole or crossed dipole. For short, these are herein called backfire antennas. Backfire antenna constructions with different configurations of the big reflector are considered. The influence of the feed location in the backfire antenna construction upon the antenn
Journal of Microwaves, Optoelectronics and Electromagnetic Applications. Publicado em: 2011-06
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14. Study on effect of rectangular DMS and DGS on 4 and 8 elements rectangular microstrip linear array antenna
In this experimental study a novel design has been developed to improve the antenna parameters in terms of impedance bandwidth and radiation properties. A 4-element rectangular array antenna (refereed as antenna 1) operating in the range of 10 to 16 GHz with multi bands is used as a reference antenna. The impedance bandwidth and other radiation properties ha
Journal of Microwaves, Optoelectronics and Electromagnetic Applications. Publicado em: 2011-06
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15. Arranjos Log-Periódicos Compactos em Microfita com Elementos Fractais de Koch / Arranjos Log-Periódicos Compactos em Microfita com Elementos Fractais de Koch
This work aims to present how the application of fractal geometry to the elements of a log-periodic array can become a good alternative when one wants to reduce the size of the array. Two types of log-periodic arrays were proposed: one with fed by microstrip line and other fed by electromagnetic coupling. To the elements of these arrays were applied fractal
Publicado em: 2010
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16. Aplicações de arranjos de antenas de microfita com patch supercondutor
This work has as main objective the study of arrays of microstrip antennas with superconductor rectangular patch. The phases and the radiation patterns are analyzed. A study of the main theories is presented that explain the microscopic and macroscopic phenomena of superconductivity. The BCS, London equations and the Two Fluid Model, are theories used in the
Publicado em: 2010
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17. Estudo da capacidade de imageamento do protótipo do brazilian decimetric array (PBDA) / Study of the imaging capability of the prototype of brazilian decimetric array (PBDA)
The prototype of the Brazilian Decimetric Array - BDA, is a one-dimensional East-West array, with 5 antennas of 4 m in diameter, with baselines ranging from 18 to 216 m, operating frequencies 1,2 - 1,7 GHz and temporal resolution of ~105 ms. The array has produced since the beginning of operations and on a regular basis, fringe visibilities in its 10 pairs o
Publicado em: 2009
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18. Uma nova antena controlada por reatância com polarização horizontal
Com a digitalização do broadcasting de TV aberta no Brasil, os efeitos de degradação do sinal digital por ação do fenômeno denominado multipercurso começam a ser observados pelo usuário, fenômeno cuja severidade é típica do cenário de operação de altas concentrações urbanas em zonas tropicais. O efeito do multipercurso é um dos fatores mais
Publicado em: 2008
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19. Aplicações de antenas adaptativas em sistemas de comunicações móveis / Applications of adaptive antennas in wireless communications systems
The increasing demand for wireless communications services has demanded the development of technologies that allow serving a bigger amount of users without increasing the bandwidth used today. It also has an increasing demand for services that need high transmission rates on mobile terminal, as Internet and video transfer. On the other hand, the user desires
Publicado em: 2007
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20. Uma nova proposta de antena planar multibanda para comunicações móveis
The great interest observed in wireless communication systems has required the development of new configurations of microstrip antennas, because they are easily built and integrated to other microwave circuit components, which is suitable for the construction and development of planar antenna arrays and microwave integrated circuits. This work presents a new
Publicado em: 2007
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21. Uma nova estratégia de otimização de arranjos interferométricos aplicada ao Brazilian Decimetric Array / A new strategy for array optimization applied to brazilian decimetric array
Radio interferometric arrays measure the Fourier transform of the sky brightness distribution in a finite set of points that are determined by the cross-correlation of different pairs of antennas of the array. The sky brightness distribution is reconstructed by the inverse Fourier transform of the sampled visibilities. The quality of the reconstructed images
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 20/03/2006
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22. Estimação da direção de chegada (DOA) de sinais eletromagnéticos em canais reversos CDMA utilizando antenas inteligentes
The great effort of communications engineers is to create methods that allows improve spectrum usage efficiency, that is a scarce resource. The Code Division Multiple Access (CDMA) and the spatial processing techniques using array of antennas are two enable technologies to achieve this task. In this context, the smart antennas technique can improve the recep
Publicado em: 2006
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23. Efeitos de acoplamento e de banda de operação em redes de antenas adaptativas reais. / Coupling and operation bandwidth effects in real adaptive antenna arrays.
Smart antenna arrays are becoming more important in the expansion and in the enhancement of cellular telephony systems, specially in the third-generation that will need an even larger bandwidth. In this subject, many contributions from the scientific community have been provided with the goal of determining direction-of-arrival for incident signals, eliminat
Publicado em: 2005
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24. Selection algorithm of spreading sequences for CDMA systems with space-time coding and antenna array / Algoritmo de escolha de sequencias de espalhamento em sistemas CDMA com codificação espaço-temporal e arranjo de antenas
The performance of mobile communication systems based on the CDMA technique is limited by interference. In this thesis, we propose a selection algorithm of spreading sequences with fixed length for interference mitigation on CDMA systems over frequency-selective fading channels, that is based on the minimization of the overall mean bit error probability of t
Publicado em: 2005