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Reducing the dispersion errors of the finite-difference time-domain method for multifrequency plane-wave excitations

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ELECTROMAGNETICS 2003年第6期23卷 539-552页

作者： Oguz, U Gürel, L Bilkent Univ Dept Elect & Elect Engn TR-06800 Ankara Turkey

We demonstrate the applications of discrete-time signal-processing (SP) techniques for the purpose of generating accurate plane waves in the finite-difference time-domain (FDTD) method. The SP techniques are used either to reduce the high-frequency content of the source excitation or to compute more precise incident-field values in the computational domain. The effects of smoothing windows of various lengths, digital lowpass filters of various bandwidths and characteristics, and polynomial interpolation schemes of various orders are investigated. Arbitrary signals with multifrequency content are considered.

关键词： finite-difference time-domain method plane-wave excitation numerical dispersion sampling windowing digital filters

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An upwinding boundary condition capturing method for Maxwell's equations in media with material interfaces

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JOURNAL OF COMPUTATIONAL PHYSICS 2007年第1期225卷 342-362页

作者： Xue, Changfeng Deng, Shaozhong Univ N Carolina Dept Math & Stat Charlotte NC 28223 USA Yancheng Inst Technol Dept Fundamental Sci Yancheng 224003 Jiangsu Peoples R China Peking Univ State Key Lab Turbulence & Complex Syst Beijing 100871 Peoples R China

By using ghost points on either side of the interfaces, a global second-order accurate upwinding boundary condition capturing method for time-domain Maxwell's equations in media with material interfaces is proposed. The equations are discretized on a uniform Cartesian grid and the interfaces are allowed to intersect the grid in an arbitrary fashion. The method is then obtained by combining central finite difference schemes with applicable nodes being replaced by the ghost points and upwinding technique with jump conditions across the interfaces being captured in a manner that the upwind property is always satisfied. The resulting discretization has the desirable property that the allowed time step size is independent of the locations and the shapes of the interfaces. Numerical examples are then given to demonstrate the second-order accuracy as well as the stability of the method, where it is used to study wave equations with various types of material interfaces, including electromagnetic scattering of a plane incident wave by a dielectric circular cylinder. (c) 2006 Elsevier Inc. All rights reserved.

关键词： finite-difference time-domain method ghost fluid method Maxwell's equations

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Efficient FDTD method for analysis of mushroom-structure based left-handed materials

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IET MICROWAVES ANTENNAS & PROPAGATION 2007年第1期1卷 100-107页

作者： Wu, W.-Y. Lai, A. Kuo, C. -W. Leong, K. M. K. H. Itoh, T. Natl Sun Yat Sen Univ Dept Elect Engn Kaohsiung 804 Taiwan Univ Calif Los Angeles Dept Elect Engn Los Angeles CA 90095 USA

A finite-difference time-domain method, combined with thin-wire and thin-slot algorithms, which is used to analyse a metamaterial based on periodic mushroom structures, is proposed. This proposed method is suitable for analysing problems involving large structures with fine structural details. Several composite right/left handed (CRLH) metamaterial mushroom-based structures are investigated. A 19 x 8 flat lens and a parabolic lens structure composed of 410 unit mushroom cells are investigated and they demonstrate negative-refractive-index characteristics while operating in the LH region. The simulation and measurement results of one- and two-dimensional CRLH mushroom-based structures are compared. The periodic analysis for mushroom structures is also introduced. Only a single unit mushroom cell is required to present the phenomena of infinite periodicity with periodic boundary conditions.

关键词： Microwave materials metamaterials thin-wire algorithms flat lens Other numerical methods periodic analysis periodic structures periodic mushroom structures metarnaterial FDTD method fine structural details finite difference time-domain analysis periodic boundary conditions large structures thin-slot algorithms mushroomstructure based left-handed materials negative-refractive-index characteristics infinite periodicity composite right/left handed structures finite-difference time-domain method parabolic lens

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Use of conjugate dielectric and metarnaterial slabs as radomes

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IET MICROWAVES ANTENNAS & PROPAGATION 2007年第1期1卷 137-143页

作者： Cory, H. Lee, Y. J. Hao, Y. Parini, C. G. Technion Israel Inst Technol Dept Elect Engn IL-32000 Haifa Israel Univ London Queen Mary Coll Dept Elect Engn London E1 4NS England

An interesting application of left-handed metamaterials is proposed and numerically verified. Specifically, a structure consisting of a conventional dielectric slab adjacent to a metarnaterial slab of the same width but of opposite material characteristics, is used as a radome. The behaviour of the structure for normal as well as for oblique incidence is considered. The results are satisfactory in both cases. It is shown that cylindrical structures similar to the aforementioned straight structures could also be used as radomes. However, the behaviour of the structure is non-reciprocal for incoming and outgoing waves. The dispersive finite-difference time-domain method is applied to study all the structures and the numerical results verify that the straight conjugate slabs are transparent in normal incidence and reduce the reflections for oblique incidence, which are the desirable characteristics for a radome.

关键词： radomes metamaterials Microwave materials Antenna accessories finite difference time-domain analysis Dielectric materials and properties left-handed metamaterial slab finite-difference time-domain method dispersive FDTD Other numerical methods conjugate dielectric slab dielectric materials cylindrical structures

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Prediction-step staggered-in-time FDTD: An efficient numerical scheme to solve the linearised equations of fluid dynamics in outdoor sound propagation

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APPLIED ACOUSTICS 2007年第2期68卷 201-216页

作者： Van Renterghem, T. Botteldooren, D. Univ Ghent Dept Informat Technol B-9000 Ghent Belgium

The finite-difference time-domain (FDTD) method to solve the linearised equations of fluid dynamics has shown to be very powerful and useful in outdoor sound propagation. Practical applications are however limited due to the large need for computational resources. The numerical discretisation influences computational efficiency to an important degree. In this paper, some possible ways to discretise temporal derivatives are studied. Two obvious ways of time-discretisation namely staggered-in-time (SIT) and a simple collocated-in-time (CIT) scheme are compared to the prediction-step staggered-in-time (PSIT) scheme. The latter is intended to be used for the calculation of sound propagation in the typical low wind speeds encountered in the outdoor environment at low heights above the earth's surface. It was shown that the PSIT scheme is more stable than the SIT scheme, so practical calculations are possible. Computational efficiency is increased to an important degree compared to the CIT scheme. The numerical accuracy (more precisely the amplitude error) of the PSIT scheme is an important improvement upon SIT. The CIT scheme on the other hand conserves amplitude better. The amplitude error becomes larger with increasing wind speed because of some simplifications during the numerical discretisation. In low wind speeds, the PSIT algorithm can serve as an interesting compromise between numerical accuracy and the required amount of computing power. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： finite-difference time-domain method linearised equations of fluid dynamics outdoor sound propagation numerical schemes

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3D FDTD implementation for scattering of electric anisotropic dispersive medium using recursive convolution method

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INTERNATIONAL JOURNAL OF INFRARED AND MILLIMETER WAVES 2007年第7期28卷 557-565页

作者： Yang, Lixia Jiangsu Univ Dept Telecommun Engn Jiangsu 212013 Peoples R China

The finite-difference time-domain method based on recursive convoltion method (RC-FDTD) for the electric anisotropic dispersive medium is discussed in detail. To exemplify the availability of the three-dimensional RC-FDTD algorithm, the backscattering Radar-Cross-Section (RCS) of a non-magnetized plasma sphere is computed, and the numerical results are the same as the one of the Shift Operater-FDTD method, and show that the RC-FDTD method is correct and efficient. In addition, the co-polarized and cross-polarized backscattering time-domain of a magnetized plasma sphere are obtained by the RC-FDTD algorithm. The results show that when the external magnetic field is implemented, the cross-polarized component appear, evidently.

关键词： electric anisotropic dispersive medium finite-difference time-domain method electromagnetic scattering recursive convoltion method

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Exponential time differencing algorithm for Debye medium in FDTD

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INTERNATIONAL JOURNAL OF INFRARED AND MILLIMETER WAVES 2007年第11期28卷 1025-1031页

作者： Huang, Sh. J. Zhanjinag Normal Univ Dept Phys Zhanjiang 524048 Guangdong Peoples R China

The exponential time differencing (ETD) formultion is proposed for Debye medium using finite-difference time-domain (FDTD) method. The schemes of the auxiliary differential equation (ADE) and ETD algorithms are presented. The algorithms are validated by comparing the simulation results with analytical values. The ETD method costs the same memory as the ADE method, and the numerical results indicate that the ETD technique is more accurate than the ADE method.

关键词： finite-difference time-domain method exponential time differencing method auxiliary differential equation method dispersive Debye medium

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Modeling of two-photon absorption in nonlinear photonic crystal all-optical switch

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OPTICS COMMUNICATIONS 2007年第1期269卷 137-141页

作者： Maksymov, Ivan S. Marsal, Lluis F. Pallares, Josep Univ Rovira & Virgili Dept Engn Elect Elect & Automat Tarragona 43007 Spain

We present an approach of taking the two-photon absorption effect into account and apply it to analyze an all-optical switch by means of the finite-difference time-domain method. It is shown for a shortened model of the device that the impact of the two-photon absorption on the functionality of the device is drastic. Therefore, under realistic conditions, it should be borne in mind when designing all-optical devices. (c) 2006 Elsevier B.V. All rights reserved.

关键词： all-optical switching finite-difference time-domain method photonic crystal optical Kerr effect two-photon absorption

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FDTD far-field scattering amplitudes: Comparison of surface and volume integration methods

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JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER 2007年第1-3期106卷 590-594页

作者： Zhai, Peng-Wang Li, Changhui Kattawar, George W. Yang, Ping Texas A&M Univ Dept Phys College Stn TX 77843 USA Texas A&M Univ Dept Atmospher Sci College Stn TX 77843 USA

The transformation of the near-field to the corresponding far-field is a key step involved in the application of the finite-difference time-domain (FDTD) technique to the scattering of an electromagnetic wave by a dielectric particle. In practice, either a volume-integral method (VIM) or an equivalent surface-integral method (SIM) can be used to calculate the far-field. Previous studies reported in the literature demonstrated that a fine grid resolution is necessary for implementing the FDTD technique with the aforementioned VIM for electromagnetic scattering of plane waves by a dielectric particle with a large refractive index. A fine grid resolution leads to a significant amount of computational effort in terms of computer memory and CPU time, and consequently, substantially limits the applicability of the FDTD technique. In this study, we show that the SIM allows a much coarser grid resolution than that required by the VIM. The physical mechanism associated with the advantages of the SIM is also discussed. Furthermore, it is demonstrated that the same order of numerical errors for the phase function computation can be achieved using the SIM with a grid size of Delta s = lambda/40 for the two published large refractive indices, namely m = 7.1499 + i2.914 and 8.2252 + i1.6808, whereas the grid size required by the VIM, as reported in the literature, needs to be Delta s = lambda/143 or lambda/165. With the SIM, the scattering properties of particles with complex refractive indices as large as 7.1499 + i2.914 can be simulated by the FDTD technique for size parameters up to 20 by using an ordinary desktop computer. (c) 2007 Elsevier Ltd. All rights reserved.

关键词： finite-difference time-domain method light scattering phase matrix near- to far-field transformation

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FDTD solutions for the distribution of radiation from dipoles embedded in dielectric particles

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JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER 2007年第1-3期106卷 257-261页

作者： Li, Changhui Kattawar, George W. You, Yu Zhai, Pengwang Yang, Ping Texas A&M Univ Dept Phys College Stn TX 77843 USA Texas A&M Univ Dept Atmospher Sci College Stn TX USA

The finite-difference time-domain (FDTD) method is used to simulate the electromagnetic radiation emitted by an infinitesimal electric dipole embedded in a small particle with an arbitrary shape and internal composition. The far-field pattern of the radiation pertaining to dipoles embedded in a host particle is highly sensitive to the particle shape. Thus, it is possible to discriminate host particles according to their radiation patterns. The method reported here is also applicable to the study of induced Raman scattering and fluorescence phenomena and the detection of biological agents.(C) 2007 Published by Elsevier Ltd.

关键词： finite-difference time-domain method electric dipole radiation non-spherical particle

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