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Effective Permittivity (effective + permittivity)

Distribution by Scientific Domains
Engineering66%
Physics and Astronomy22%

Selected Abstracts

Adaptive neuro-fuzzy models for the quasi-static analysis of microstrip line

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2008
Celal Yildiz
Abstract This article presents a new method based on adaptive neuro-fuzzy inference system (ANFIS) to calculate the effective permittivities and characteristic impedances of microstrip lines. The ANFIS is a fuzzy inference system (FIS) implemented in the framework of an adaptive fuzzy neural network. It has the advantages of expert knowledge of FISs and learning capability of artificial neural networks. A hybrid learning algorithm, which combines the least square method and the back propagation algorithm, is used to identify the parameters of ANFIS. The results of ANFIS are compared with the results of the experimental works, quasi-static methods, and a commercial electromagnetic simulator IE3D. There is very good agreement among the results of ANFIS models and quasi-static methods, IE3D, and experimental works. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1191,1196, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23322 [source]

An electromagnetic modelling tool for the detection of hydrocarbons in the subsoil

GEOPHYSICAL PROSPECTING, Issue 2 2000
Carcione
Electromagnetic geophysical methods, such as ground-penetrating radar (GPR), have proved to be optimal tools for detecting and mapping near-surface contaminants. GPR has the capability of mapping the location of hydrocarbon pools on the basis of contrasts in the effective permittivity and conductivity of the subsoil. At radar frequencies (50 MHz to 1 GHz), hydrocarbons have a relative permittivity ranging from 2 to 30, compared with a permittivity for water of 80. Moreover, their conductivity ranges from zero to 10 mS/m, against values of 200 mS/m and more for salt water. These differences indicate that water/hydrocarbon interfaces in a porous medium are electromagnetically ,visible'. In order to quantify the hydrocarbon saturation we developed a model for the electromagnetic properties of a subsoil composed of sand and clay/silt, and partially saturated with air, water and hydrocarbon. A self-similar theory is used for the sandy component and a transversely isotropic constitutive equation for the shaly component, which is assumed to possess a laminated structure. The model is first verified with experimental data and then used to obtain the properties of soils partially saturated with methanol and aviation gasoline. Finally, a GPR forward-modelling method computes the radargrams of a typical hydrocarbon spill, illustrating the sensitivity of the technique to the type of pore-fluid. The model and the simulation algorithm provide an interpretation methodology to distinguish different pore-fluids and to quantify their degree of saturation. [source]

Method of moments modelling of cylindrical microwave integrated circuits interconnections

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 2 2004
M. S. Al Salameh
Abstract In this paper, a numerical technique suitable for characterizing a wide variety of interconnection configurations printed on cylindrical surfaces, is presented. The interconnection lines may have either finite or infinitesimal cross-sections. To model cylindrical interfaces, suitable space-domain integral equations are formulated to represent the potential on conductors and electric field at dielectric interfaces. The solution of the integral equations is then obtained numerically by applying the method of moments (MOM). The objective of this approach is to determine the capacitance matrix of cylindrical interconnection systems with different configurations. From the capacitance matrix, other quantities such as characteristic impedance, coupling coefficient and effective permittivity can be determined. The numerical technique described in this paper is implemented as a general computer program. Various circular cylindrical as well as elliptical cylindrical structures have been solved including microstrip lines and coplanar waveguide lines. The results obtained compare very well with other published data. Copyright © 2004 John Wiley & Sons, Ltd. [source]

A directive dual-band and dual-polarized antenna with zero index metamaterial

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2008
Zi-Bin Weng
Abstract A novel directive dual-band and dual-polarized microstrip antenna with ZIM is presented. An averaging effect over constituent materials of the metamaterial structure yields an effective permittivity that approaches zero at dual band with different polarizations, and then it results in a metamaterial with zero index of refraction and the radiation energy of this antenna is congregated. The experimental results show that this method is effective, and this structure can greatly increase the gain at dual frequencies. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2902,2904, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23855 [source]

An analysis of substrate effects on transmission-lines for millimeter-wave CMOS RFIC applications

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008
Jin-Fa Chang
Abstract A set of transmission lines (TLs) for millimeter-wave (MMW) CMOS RFIC applications was implemented in a standard 0.18 ,m CMOS technology and then postprocessed by CMOS-compatible inductively-coupled plasma (ICP) etching, which removed the silicon underneath the TLs completely. TL parameters such as characteristic impedance ZC, attenuation constant ,, phase constant ,, effective permittivity ,eff, minimum noise figure (NFmin), parallel capacitance/conductance C/G, and series inductance/resistance L/R, as a function of frequency were extracted. It was found that ,, ,eff, NFmin, C, and G were greatly improved after silicon removal. The state-of-the-art performances of the on-chip TLs-on-air suggest that they are very suitable for application to realize ultralow-noise MMW CMOS RFICs. Besides, the CMOS-compatible backside ICP etching technique is very promising for MMW system-on-a-chip applications. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 319,324, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23055 [source]

Simplified description of asymmetric right-handed composite right/left-handed coupler in microstrip chip technology

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007
Youzhen Wang
Abstract The coupling frequency range of the asymmetric coupler composed of a conventional microstrip right-handed (RH) transmission line and a composite right/left-handed (CRLH) transmission line with lumped-elements is investigated. It shows theoretically that the coupling frequency range can be explicitly determined by the given formulas. In the coupling frequency range, the effective permittivity and permeability of the CRLH transmission lines are both negative, at the same time the product of the average permittivity and the average permeability is negative, i.e., ,L < 0, ,L < 0, and · < 0. Two types of RH-CRLH couplers are designed, simulated, and measured. The coupling frequency range obtained from the simulated and the experimental results confirms the theoretical results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2063,2068, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22643 [source]

Design and double negative property verification of C band left-handed metamaterial

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2006
Fan-Yi Meng
Abstract In this article, a left-handed (LH) metamaterial with miniaturized unit cell and broad bandwidth is designed. Its relative bandwidth is 56.4%, and the unit cell electrical size is 0.067 at the central frequency where the LH metamaterial is available. The effective permittivity and effective permeability are extracted from the transmission and reflection data at normal incidence for the LH metamaterial proposed here. The double negative (DNG) property is shown by the simultaneously negative effective permittivity and effective permeability and is confirmed by the equivalent circuit. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1732,1736, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21763 [source]

Magnetoimpedance (MI) in amorphous wires: new materials and applications

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2009
Larissa V. Panina
Abstract The discovery of the magnetoimpedance (MI) effect in 1994 had a strong impact on the development of magnetic sensors. Along with traditional areas of sensing applications (data storage, bio-medical electronics, robotics and security), the MI elements have a high potential for applications in smart sensory systems (self-sensing composites) operating at microwave frequencies owing to still very large MI ratios of 50,100% in Co-rich amorphous wires at GHz frequencies. Here we introduce two types of MI wire composites: 2D-arrays and mixtures of wire pieces. In such materials the effective permittivity has strong dispersion in a frequency band determined by a plasma frequency or a dipole resonance, respectively. If MI wires are used as constituent elements, this dispersion may be very sensitive to the magnetic properties of wires since the wire impedance determines the relaxation parameter of the effective permittivity. For example, increasing the wire impedance by establishing the magnetisation along the axis with an external magnetic field broadens the resonance band, decreases the reflection amplitude and may open a bandpass. Depending on the magnetic anisotropy in wires, tuning can be realized with both magnetic field and stress. It is foreseen that MI-wire composite materials could be suitable for large scale applications, in particular, for free space filters in secure wireless systems and for microwave nondestructive testing and control in civil engineering. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

s-polarization Brewster's angle of stratified metal,dielectric metamaterial in optical regime

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2008
Ryosuke Watanabe
Abstract We demonstrate that the optical reflectivity for s-polarized light vanishes at a certain angle in a stratified metal,dielectric metamaterial numerically and experimentally. The metamaterial consists of a unit cell where a Ag layer of 30 nm thickness is sandwiched by Al2O3 layers of 60 nm thickness. In order to understand the phenomenon in terms of effective permittivity and permeability, we extended a field-sampling method. The permeability is found to be significantly different from unity, which is the origin of Brewster's angle for s-polarization. The microscopic field distribution is readily coarse grained with the effective optical parameters. The present result is a manifestation of the magnetic response in the optical regime. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]