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Dielectric Slab (dielectric + slab)
Selected AbstractsNeural model of microwave cylindrical cavity loaded with arbitrary-raised dielectric slabINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2009Stankovi, Zoran Abstract A combined knowledge-based neural-multilayer perceptron (KBN-MLP) model to account for a loading effect of arbitrary raised dielectric slab in a microwave cylindrical metallic cavity is presented. Existing partial knowledge about the resonant frequency behavior of loaded cavity is incorporated in the KBN part of suggested model. In comparison with the model based on classical MLP network, more accurate and efficient resonant frequencies calculation is achieved. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [source] Miniaturized rectangular waveguide filtersINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2007Alexander Shelkovnikov Abstract Two types of miniaturized rectangular waveguide filters are presented. Miniaturization is achieved using the slow-wave effect of electromagnetic bandgap (EBG) surfaces and the left-handed properties of split ring resonators (SRRs). The proposed EBG waveguide bandpass filter performs passband in the frequency range, which corresponds to the waveguide with the lower recommended operating band consequently enabling significant miniaturization of the structure. The SRR-loaded bandstop filter makes use of the effect imposed by left-handed medium (LHM), which is created by a combination of SRRs and wireline on the dielectric slab. Both filters are designed, simulated, and tested. Experimental results of the SRR-loaded bandstop filter are presented to demonstrate feasibility of the proposed structures. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [source] Simulation of an aperture in the thick metallic screen that gives high intensity and small spot size using surface plasmon polaritonJOURNAL OF MICROSCOPY, Issue 3 2003K. Tanaka Summary The optical wave behaviour around a subwavelength aperture in a thick metallic screen is examined through three-dimensional computer simulation. Treating the metallic screen as a dielectric slab with complex-valued permittivity, it is possible to design an aperture that simultaneously provides high intensity and small spot size through the excitation of surface plasmon polaritons on the side walls of the aperture. [source] Effective dielectric constant and design of sliced Lüneberg lensMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2007Georgios Zouganelis Abstract In this article, a design of Lüneberg lens with slices made from low loss dielectric material with hemispherical air-holes drilled appropriately on the top and bottom surface of each of them is presented. A formula to estimate the values of radial dependent effective dielectric constant of air-holes dielectric composite material is suggested. The estimated values are compared with the ones calculated from finite difference time domain method electromagnetic simulations of a periodic lattice of spherical and cylindrical air-holes embedded in a dielectric slab using Nicolson,Ross method. Calculation of S-parameters and near field of lens with hemispherical air-holes under an incident plane wave, using estimated effective constants by the suggested formula are compared with ones using precise theoretical values of dielectric constants. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2332,2337, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22751 [source] Disorder-induced modification of the attenuation of light in a two-dimensional photonic crystal with complete band gapPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2003M. A. Kaliteevski Abstract We report on the modeling of light transmission in disordered two-dimensional photonic crystals (formed by air cylinders etched in a dielectric slab) with a complete photonic band gap. The disorder leads to a decrease in the light attenuation in the transmission dip corresponding to the photonic band gap, both for straight and scattered transmission, but the dependence of the attenuation length on the disorder is quite different for straight and scattered transmission. In the case of the straight transmission, there is a threshold degree of disorder required for the increase of the attenuation length. Disorder leads to a substantial modification of the spectral shape in the frequency region, corresponding to the photonic band gap, in particular, to the decrease of the width of the spectral dependence of the inverse attenuation length. We also demonstrate the appearance of photonic mini-bands in the photonic band gaps in the case of disorder represented by randomly distributed ,vacancies' of the air-cylinders. [source] A study of uniform approximation of equivalent permittivity for index-modulated gratingsELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 11 2008Shota Sugano Abstract It is well known that surface-relief dielectric gratings with rectangular profile can be treated by uniform approximation of the equivalent permittivity when the periodicity is very small compared with the wavelength. In optics, this phenomenon is the equivalent anisotropic effects or the form birefringence. When the periodicity is very small, the equivalent anisotropic effects will be shown in index-modulated gratings. In this paper, the uniform approximation is described for the electromagnetic scattering problem of index-modulated gratings. The scattering properties of dielectric slabs are calculated by transmission-line theory and the equivalent permittivity obtained from our proposed formulation of the uniform approximation. Scattering by index-modulated gratings is analyzed rigorously by matrix eigenvalue calculations using the Fourier expansion method and spatial harmonics expansions. When the periodicity is very small, the results are in good agreement. By investigating the difference between the equivalent permittivity and the numerical values corresponding to the permittivity of the index-modulated gratings, the conditions of applicability of the uniform approximation are shown. The equivalent anisotropic effects of various profiles are compared. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 91(11): 28,36, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10181 [source] Effect of Fabry-Perot resonances in disordered one-dimensional array of alternating dielectric bi-layersANNALEN DER PHYSIK, Issue 12 2009G.A. Luna-Acosta Abstract We study numerically and analytically the role of Fabry-Perot resonances in the transmission through a one-dimensional finite array formed by two alternating dielectric slabs. The disorder consists in varying randomly the width of one type of layers while keeping constant the width of the other type. Our numerical simulations show that localization is strongly inhibited in a wide neighborhood of the Fabry-Perot resonances. Comparison of our numerical results with an analytical expression for the average transmission, derived for weak disorder and finite number of cells, reveals that such expression works well even for medium disorder up to a certain frequency. Our results are valid for photonic and phononic one-dimensional disordered crystals, as well as for semiconductor superlattices. 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