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Effective Dielectric Constant (effective + dielectric_constant)

Distribution by Scientific Domains

Engineering	60%
Polymers and Materials Science	30%

Selected Abstracts

Effective dielectric constant and design of sliced Lüneberg lens

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2007
Georgios 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]

Full-wave analysis of single cylindrical striplines and microstriplines with multilayer dielectrics

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 8 2006
Farid Bouttout
Abstract In this paper, the spectral-domain method is used to calculate the propagation characteristics of cylindrical microstrip transmission lines. The problem is formulated using an electric field integral equation and the spectral-domain Green's function. The solutions of the field components are obtained in matrix forms, which facilitate the calculations of the Green's function and the power flowing over the lines. The Green's functions are obtained in terms of transition matrices over the dielectric layers. The obtained integral equation is solved by moment method using four kinds of basis functions. The convergence of the method is proven. Based on the power,current definition, a stationary expression for the characteristic impedance has been derived analytically. Numerical results of the effective dielectric constant and the characteristic impedance for various line parameters are calculated and analysed. The computed data are found to be in good agreement with results obtained using other methods. The formulation is then applied to covered microstripline, microstripline and stripline with air gaps, for which data are not found in the literature to date. The presented method is used to guide design of microstrip coil for magnetic resonance imaging. This method is also suitable for investigation of multiconductor strip lines. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Prediction of the effective dielectric constant in SWNT polyimide nanocomposites using the Bruggemann model

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009
Ricardo PérezArticle first published online: 27 APR 200
Abstract The Bruggemann model is used in this work to predict the effective dielectric constant of two kinds of single-wall carbon nanotube (SWNT) polyimide nanocomposites. Electrical conductivity and dielectric constant exhibit a dramatic enhancement at low content of SWNT fillers with a percolation threshold at 0.06 vol %. Results of the Bruggemann model are compared with the experimental values of the dielectric constant in CP2/SWNT and ,CN/SWNT polyimide nanocomposites. A reasonable agreement for SWNT contents under the percolation threshold and a SWNT dielectric constant of 2000 was found between the Bruggeman model modified by Giordano and the experimental values. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

Base-Metal-Electroded BaTiO3 Capacitor Materials with Duplex Microstructures

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2004
I-Nan Lin
The effect of dopants and processing conditions on the dielectric properties of base-metal-electroded materials was investigated. BaTiO3 materials simultaneously doped with MgO and Y2O3 additives can achieve small capacitance variation (,C/C), which meets the X7R specification, when the proportion of additives is abundant enough and the materials are not over-fired. Presumably, small ,C/C values of thus obtained materials are the result of the formation of core,shell structure, which requires stringent control of material processing conditions. In contrast, X7R-type materials can be obtained in a much wider processing window, when prepared by mixing two BaTiO3 materials of suitable dielectric constant,temperature (K,T) characteristics. Duplexed materials prepared from these two end-point BaTiO3 materials with ratios ranging from 3:1 to 1:2 exhibit K,T behavior within the X7R specification, provided that one of the components possesses flat K,T behavior. Moreover, the dielectric properties of these materials were simulated using a simplified microstructural model. Simulation results indicate that the effective dielectric constant of core,shell materials, (Ke)CS, varies significantly not only with the dielectric properties of cores and shells, but also with the shell-to-core thickness ratio, whereas the effective dielectric constant of duplexed materials, (Ke)D, can be maintained at a very small ,C/C value for a wide range of end-point constituent ratios, which agrees very well with the measured K,T properties for the materials. [source]

Size reduction of microwave and millimeter-wave passive circuits by UC-PBG in standard 0.18-,m CMOS technology

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2008
Shuiyang Lin
Abstract Size reduction of microwave and millimeter-wave (mm-wave) passive circuits incorporating a defective uniplanar compact photonic bandgap (UC-PBG) slow-wave structure is investigated. Benefited from the multilayer mental technology of the standard 0.18-,m CMOS process, thin film microstrip structure is properly constructed on the lossy silicon substrate to reduce substrate loss. Defected periodic patterns on the ground plane are used to contribute to an enhancement of the effective dielectric constant and the slow-wave factor is 14% increased by the use of UC-PBG ground. Microwave and mm-wave passive circuits including resonator and filter are designed and fabricated. Measured results show that the use of UC-PBG ground has induced a frequency drop of 14% and validate the size reduction concept by using UC-PBG. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2251,2254, 2008; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.23643 [source]

Effective dielectric constant and design of sliced Lüneberg lens

Determination of microwave dielectric constant by two microstrip line method combined with EM simulation

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2006
Sheng-Hsiung Chang
Abstract This paper presents a modified procedure to determine the microwave dielectric constant of substrate by two microstrip line method combined with EM simulation. The dielectric constant of substrate is mapped from the measured transmission phase with those of EM simulation, instead of using the closed form equations between the effective dielectric constant and dielectric constant. A tested example of dielectric constant of FR4 substrate is experimented and extracted to verify the proposed procedure. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2199,2201, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21936 [source]

New expression for the resonance frequency of an E-shaped microstrip patch antenna

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2006
Dipak K. Neog
Abstract The resonance frequency of an E-shaped microstrip antenna has been calculated by equating its area to an equivalent area of a rectangular microstrip patch antenna. A new expression for effective dielectric constant is developed for the E-shaped microstrip patch antenna. The new expression of resonance frequency is used to calculate the results, which are in good agreement with the measured and published results. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1561,1563, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21700 [source]

Study of metal-oxide-semiconductor capacitors with r.f. magnetron sputtering TiOxNy films dielectric layer

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
Katia Franklin Albertin
Abstract A set of MOS capacitors with TiOxNy films as gate dielectric layer was fabricated and characterized. The TiOxNy films were deposited by reactive r.f. magnetron sputtering varying the nitrogen and oxygen partial pressure in a Ar/N2/O2 gaseous mixture. The TiOxNy films were characterized by, Rutherford Backscattering (RBS), X-ray absorption near edge spectroscopy (XANES) in oxygen K-edge (O-K), optical absorption and High Resolution Transmission Electron Microscopy (HRTEM). Capacitance-voltage (1MHz) and current-voltage measurements were performed to obtain the effective dielectric constant, the effective oxide thickness (EOT), the leakage current density, and the interface quality. MOS capacitors results show that the TiOxNyfilms dielectric constant varies from 28 to 80, present a good interface quality with silicon, and the leakage current density values are in the order of 0.25 mA/cm2 for VG = ,2V, which is acceptable for high performance logic circuits and low power circuits fabrication. The leakage current density is reduced in 2 orders of magnitude for increasing nitrogen concentration (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]