Navegando por Autor "KAWAKATSU, Marcelo Nobuyuki"

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Microwave switchable frequency selective surface with high quality factor resonance and low polarization sensitivity
(2012-12) KAWAKATSU, Marcelo Nobuyuki; DMITRIEV, Victor Alexandrovich
We present a microwave switchable frequency selective surface with high quality factor transmission resonance. The high quality resonance is achieved by excitation of the trapped-mode in array with two concentric metal rings in a cell on a silicon substrate. Optical activation of the silicon substrate permits to switch off the transmission band.
Acesso aberto (Open Access)
Otimização de antenas lineares e planares para aplicações em sistemas de banda larga
(Universidade Federal do Pará, 2009-10-16) KAWAKATSU, Marcelo Nobuyuki; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
The objective of this work is the bandwidth optimization of linear and planar antennas for broadband system applications. For achieving this goal, it was made a study of the analysis, bandwidth enlargement and optimization techniques appropriated for the problem in question. As analysis technique, the method of moments was utilized, which is presented in chapter II. For bandwidth enlargement, the techniques of collocation of parasitic elements and building slots in the radiator were employed, briefly described in chapter III. As optimization algorithm, the genetic algorithm was utilized, briefly described in chapter II. In this work, two antenna proposals are presented, a linear dipole antenna combined with four parasitic elements, chapter IV, and a planar antenna of loop type, chapter V. In the first case, it was utilized parasitic elements and the genetic algorithm to enlarge the bandwidth, and in the second, it was employed slots in the radiator and the parametric optimization to this objective.
Acesso aberto (Open Access)
Superfícies eletromagnéticas de microondas com controle do regime de trapped-mode
(Universidade Federal do Pará, 2012-03-09) KAWAKATSU, Marcelo Nobuyuki; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
In this work frequency selective surfaces (FSSs) with high quality factor (Q-factor) resonance and polarization independence for a normally incident plane wave were investigated. These FSSs are based on a planar array of metallization on a substrate. A high Q-factor is obtained by excitation of trapped-mode and polarization independence by means of high rotational symmetry of the elements that compose the array. For the design of FSSs with trapped-mode regime control, substrates made of materials with the possibility of controlling their electric or magnetic properties (magnetized ferrite or optically activated silicon) were used. The two concentric rings array on a dielectric substrate analyzed in this work presents a trapped-mode resonance with a Q-factor around 12 and maximum transmittance of 70 %. With the utilization of a magnetized ferrite substrate in this array, it is shown that we can shift the resonance frequency of the trappedmode around 20 % without significant degradation of the transmission resonance. With the use of an optically activated silicon substrate, it is demonstrated the possibility of an almost complete switching of the transmission band in that array. To perform the computer simulations the spectral domain moment method (SDMM) and the commercial programs Ansoft Designer 5 PlanarEM and CST 2009 were used.