The Experts below are selected from a list of 3597 Experts worldwide ranked by ideXlab platform
Kin-lu Wong - One of the best experts on this subject based on the ideXlab platform.
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Analysis of a cylindrical-rectangular microstrip structure with an airgap
IEEE Transactions on Microwave Theory and Techniques, 1994Co-Authors: Kin-lu Wong, Yuan-tung ChengAbstract:The resonance problem of the cylindrical-rectangular microstrip structure with an airgap between the substrate layer and the ground conducting cylinder is studied by using a rigorous full-wave approach and a moment method calculation. The resonance condition is satisfied by complex resonant frequencies, which provide the information of resonant frequency and Half-Power Bandwidth of the structure. Numerical results indicate that, with the increasing of the airgap thickness, the Half-Power Bandwidth of the structure at the efficient radiating mode of HE/sub 0.1/ is considerably increased, which improves the narrow Bandwidth characteristics of microstrip structures. Details of the numerical results, including the results for the planar rectangular microstrip structure with an airgap, are presented and analyzed.
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Resonance in a spherical-circular microstrip structure with an airgap
IEEE Transactions on Microwave Theory and Techniques, 1993Co-Authors: Kin-lu Wong, Hong-twu ChenAbstract:The resonance problem of the spherical-circular microstrip structure with an airgap between the substrate layer and the ground conducting sphere is studied by using a rigorous Green's function formulation in the spectral domain and Galerkin's moment method calculation. Complex resonant frequencies are obtained in this study, which provide the resonant frequencies and Half-Power Bandwidth of the structure. From the numerical results, it is found that with the increasing of the airgap thickness, the Half-Power Bandwidth of the structure is considerably increased. This improves the low-Bandwidth characteristics of microstrip structures. Details of the numerical results are presented and discussed.
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Resonance and radiation of a superstrate-loaded spherical-circular microstrip patch antenna
IEEE Transactions on Antennas and Propagation, 1993Co-Authors: Kin-lu Wong, Sun-fu Hsiao, Hong-twu ChenAbstract:The effects of the dielectric superstrate cover on the resonance and radiation problems of a spherical-circular microstrip patch antenna are studied, using the Green's function formulation in the spectral domain and the Galerkin moment method calculation. Numerical results for the resonant frequency, Half-Power Bandwidth, and radiation pattern of the superstrate-loaded antenna are presented. The effects of curvature on these characteristics are also shown. >
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Resonance of a rectangular microstrip patch on a uniaxial substrate
IEEE Transactions on Microwave Theory and Techniques, 1993Co-Authors: Kin-lu Wong, Jeen-sheen Row, Chih-wen Kuo, Kuang-chi HuangAbstract:Effects of uniaxial anisotropy in the substrate on the complex resonant frequency of the microstrip patch antenna are investigated in terms of an integral equation formulation. The complex resonant frequency of the microstrip patch antenna is calculated using Galerkin's method to solve the integral equation. The sinusoidal functions that are selected as the basis functions, which show fast numerical convergence. Numerical results indicate that both the resonant frequency and the Half-Power Bandwidth are increased due to positive uniaxial anisotropy and decreased due to negative uniaxial anisotropy. >
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Resonance in a Spherical-Circular Microstrip
1991Co-Authors: Kin-lu Wong, Hong-m ChenAbstract:ibstruct-The resonance problem of the spherical-circular microstrip structure with an airgap between the substrate layer and the ground conducting sphere is studied by using a rigorous Green's function formulat ion in the spectral domain and Galerkin's moment method calculation. Crmplex resonant frequencies are obtained in this study, which provide thv resonant frequencies and Half-Power Bandwidth of the structure. Frm the numerical results, it is found that with the increasing of the airga 3 thickness, the Half-Power Bandwidth of the structure is considerably inc reased. This improves the low-Bandwidth characteristics of microstrip structures. Details of the numerical results are presented and discussed.
Geert Degrande - One of the best experts on this subject based on the ideXlab platform.
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Multimodal determination of Rayleigh dispersion and attenuation curves using the circle fit method
Geophysical Journal International, 2017Co-Authors: Ramses Verachtert, Geert Lombaert, Geert DegrandeAbstract:In a multi-channel analysis of surface waves (MASW) experiment, inversion of Rayleigh wave dispersion and attenuation curves is used to determine the shear wave velocity and material damping ratio of shallow soil layers. Peak picking and the Half-Power Bandwidth method can be used to determine the dispersion and attenuation curves, respectively. In this paper, the circle fit method is proposed to improve the determination of multi-modal dispersion and attenuationn curves. A numerical MASW experiment is simulated for a layered Halfspace, corresponding to a site in Lincent (Belgium). It is shown that the circle fit method results in more accurate estimations of multi-modal dispersion curves than peak picking. Both the circle fit and Half-Power Bandwidth method result in reliable attenuation curves of dominant modes. For other modes an alternative more robust measure of attenuation, based on the circle fit method, is proposed which would enable inversion of these modes.
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Determination of the material damping ratio in the soil from SASW tests using the Half-Power Bandwidth method
Geophysical Journal International, 2010Co-Authors: Sayedali Badsar, Mattias Schevenels, Wim Haegeman, Geert DegrandeAbstract:SUMMARY This paper presents a novel technique for the determination of the material damping ratio in shallow soil layers. It is based on the spectral analysis of surface waves (SASW) test. The technique is an alternative to existing methods, where the damping ratio is determined from the spatial decay of the Rayleigh wave. These methods rely on the knowledge of the geometric damping, and may lead to incorrect results if the geometric damping is calculated based on an inaccurate shear wave velocity profile. The existing methods may also lead to incorrect results when higher modes contribute to the wavefield in the soil. In the proposed technique, the wavefield is transformed to the frequency–wavenumber domain. The resulting frequency–wavenumber spectrum exhibits a peak that corresponds to the fundamental Rayleigh wave. The dispersion curve is derived from the peak’s position, whereas the attenuation curve is derived from its width, using the Half-Power Bandwidth method. Due to the use of the appropriate wavenumber transformation, this method does not require the calculation of the geometric damping. In addition, the occurrence of higher Rayleigh modes does not affect the attenuation curve associated with the fundamental Rayleigh wave, as higher modes appear as separate peaks in the frequency–wavenumber spectrum that do not interfere with the peak corresponding to the fundamental Rayleigh wave (except at the osculation points). Three benchmark problems are considered to validate the outlined technique; the results are compared with those obtained using existing methods. All methods perform well when applied to a regular soil profile, where the stiffness of the soil increases with depth. For soil profiles with a soft layer trapped between two stiffer layers, or where the soil properties vary smoothly with depth, the proposed technique yields more accurate results than the existing methods. The practical applicability of the new method is finally illustrated using experimental data collected from a test site in Belgium.
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Determination of the Damping Ratio in the Soil from SASW Tests Using the Half-Power Bandwidth Method and Arias Intensity
Near Surface 2010 - 16th EAGE European Meeting of Environmental and Engineering Geophysics, 2010Co-Authors: Sayedali Badsar, Mattias Schevenels, Wim Haegeman, Geert DegrandeAbstract:This paper focuses on the determination of the material damping in the soil by means of the SASW test. Two new methods are proposed. The first method is based on the Half-Power Bandwidth method applied to the width of the peaks in the $f$--$k$ spectrum to determine the attenuation of Rayleigh waves. The second method uses the spatial decay of the Arias intensity at the surface to determine the material damping ratio. Both methods are used to determine the material damping ratio in the soil at a site in Belgium. The identified soil profiles are used to simulate the wave field registered in the SASW test, which is confronted with the experimental data. Good results are obtained with both methods, the second method performing slightly better than the first.
Hong-twu Chen - One of the best experts on this subject based on the ideXlab platform.
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Resonance in a spherical-circular microstrip structure with an airgap
IEEE Transactions on Microwave Theory and Techniques, 1993Co-Authors: Kin-lu Wong, Hong-twu ChenAbstract:The resonance problem of the spherical-circular microstrip structure with an airgap between the substrate layer and the ground conducting sphere is studied by using a rigorous Green's function formulation in the spectral domain and Galerkin's moment method calculation. Complex resonant frequencies are obtained in this study, which provide the resonant frequencies and Half-Power Bandwidth of the structure. From the numerical results, it is found that with the increasing of the airgap thickness, the Half-Power Bandwidth of the structure is considerably increased. This improves the low-Bandwidth characteristics of microstrip structures. Details of the numerical results are presented and discussed.
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Resonance and radiation of a superstrate-loaded spherical-circular microstrip patch antenna
IEEE Transactions on Antennas and Propagation, 1993Co-Authors: Kin-lu Wong, Sun-fu Hsiao, Hong-twu ChenAbstract:The effects of the dielectric superstrate cover on the resonance and radiation problems of a spherical-circular microstrip patch antenna are studied, using the Green's function formulation in the spectral domain and the Galerkin moment method calculation. Numerical results for the resonant frequency, Half-Power Bandwidth, and radiation pattern of the superstrate-loaded antenna are presented. The effects of curvature on these characteristics are also shown. >
Hosung Choo - One of the best experts on this subject based on the ideXlab platform.
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Novel UHF RFID Tag Antenna for Metallic Foil Packages
IEEE Transactions on Antennas and Propagation, 2012Co-Authors: Jeongki Ryoo, Jaeyul Choo, Hosung ChooAbstract:A low-cost wideband antenna for radio-frequency identification (RFID) tags for use with metallic foil packages is designed in this communication. An proximity inductively coupled feed structure is employed to perform wideband impedance matching between a slot on a metallic foil package and a small rectangular feeding loop connected to a microchip. The results show a measured Half-Power Bandwidth of 32.2% (799 MHz-1,093 MHz) and a reading distance of over 10 m.
Jose M. Roesset - One of the best experts on this subject based on the ideXlab platform.
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evaluation of the Half Power Bandwidth method to estimate damping in systems without real modes
Earthquake Engineering & Structural Dynamics, 2010Co-Authors: B.a. Olmos, Jose M. RoessetAbstract:The objective of this work was to assess the significance of the values of damping obtained applying the Half-Power Bandwidth method to the frequency response records of the steady-state response of a system that does not possess real modes either because the damping matrix does not satisfy the orthogonality condition or because its parameters are functions of frequency. A multi-degree of freedom system with real modes and different types of damping is considered first. A two degree of freedom system with an arbitrary damping matrix, a rigid mass on an elastic foundation subjected to vertical and coupled horizontal/rocking vibrations, and a single degree of freedom model of a building accounting for inertial soil structure interaction effects are considered next in more detail. The results show that the predictions of the method, when applicable compare very well with those provided by approximate formulae and procedures used in practice. Copyright © 2010 John Wiley & Sons, Ltd.
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Evaluation of the Half‐Power Bandwidth method to estimate damping in systems without real modes
Earthquake Engineering & Structural Dynamics, 2010Co-Authors: B.a. Olmos, Jose M. RoessetAbstract:The objective of this work was to assess the significance of the values of damping obtained applying the Half-Power Bandwidth method to the frequency response records of the steady-state response of a system that does not possess real modes either because the damping matrix does not satisfy the orthogonality condition or because its parameters are functions of frequency. A multi-degree of freedom system with real modes and different types of damping is considered first. A two degree of freedom system with an arbitrary damping matrix, a rigid mass on an elastic foundation subjected to vertical and coupled horizontal/rocking vibrations, and a single degree of freedom model of a building accounting for inertial soil structure interaction effects are considered next in more detail. The results show that the predictions of the method, when applicable compare very well with those provided by approximate formulae and procedures used in practice. Copyright © 2010 John Wiley & Sons, Ltd.
