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finite-difference time-domain modeling of a corrugated horn antenna as a radar system feed

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS 2005年第4期47卷 384-387页

作者： Farahat, N Mittra, R Carrion, J Polytech Univ Puerto Rico Elect & Comp Engn Dept San Juan PR 00919 USA Penn State Univ Electromagnet Commun Lab University Pk PA 16802 USA

The design of a reflector-antenna feed for monopulse tracking-radar application is presented. The feed consists of a rectangular-circular mode coupler to isolate the stun and difference channels required for monopulse tracking, and a corrugated horn for a symmetric radiation pattern with low cross polarization. The modeling is carried out using the finite-difference time-domain (FDTD) method, which is well suited for field visualization. The measurements show that the feed performance meets the design requirements and is in close agreement with the FDTD prediction. (c) 2005 Wiley Periodicals, Inc.

关键词： finite-difference time-domain method bode of revolution corrugated horn reflector antenna feed monopulse tracking radar

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Numerical dispersion and dissipation error of the 2-D PLCDRC-FDTD method for plasmas

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IEE PROCEEDINGS-MICROWAVES ANTENNAS AND PROPAGATION 2005年第3期152卷 189-194页

作者： Liu, SB Yuan, N Liu, SQ Mo, J Nanchang Univ Sch Sci Nanchang 330047 Peoples R China Natl Univ Def Technol Sch Elect Sci & Engn Changsha 410073 Peoples R China

Recently, a new finite-difference time-domain method for dispersive media called the piecewise linear current density recursive convolution finite-difference time-domain (PLCDRCFDTD) method has been published. The numerical dispersion relation of the 2-D PLCDRCFDTD method for plasma is derived. With the numerical dispersion relation, the numerical dispersion error and dissipation error caused by the PLCDRC-FDTD method are investigated by comparing the real part and imaginary part of a numerical index of refraction with those of an analytic index of refraction. The relationships between the numerical dispersion, dissipation errors and different parameters (i.e. EM wave frequency, plasma frequency, collision frequency) are studied.

关键词： piecewise linear current density recursive convolution electromagnetic wave propagation dispersion error plasmas finite difference time-domain analysis current density numerical dispersion Numerical approximation and analysis dispersive media refractive index piecewise linear techniques Electromagnetic wave propagation in plasma Other numerical methods plasma electromagnetic wave propagation finite-difference time-domain method dissipation error 2-D PLCDRC-FDTD method

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Analysis and reduction of electromagnetic field leakage through loaded apertures: A numerical study

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ELECTROMAGNETICS 2005年第7-8期25卷 679-693页

作者： Ramahi, OM Li, L Univ Waterloo Dept Elect & Comp Engn Waterloo ON N2T 2H4 Canada Univ Maryland A James Clark Sch Engn CALCE Elect Prod & Syst Ctr Dept Mech Engn College Pk MD 20742 USA

This paper presents the novel use of resistive sheets to reduce electromagnetic penetration through apertures. The resistive material is applied in several configurations that will be discussed in this paper. Significant reduction of electromagnetic leakage is possible by using loading techniques inspired by a transmission line interpretation of the field distribution within the aperture at or beyond its fundamental resonant frequency. By using the configurations proposed in this work, it is possible to achieve appreciable reduction in the near and far field aperture radiation without affecting the total area needed for airflow and heat transfer. Numerical results are presented using a commercial finite-difference time-domain (FDTD) algorithm to demonstrate the effectiveness of our new approach.

关键词： electromagnetic compatibility electromagnetic interference aperture coupling finite-difference time-domain method

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Design tips of nanoapertures with strong field enhancement and proposal of novel L-shaped aperture

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OPTICAL ENGINEERING 2005年第1期44卷 1-9页

作者： Xu, JY Xu, TJ Wang, J Tian, Q Tsinghua Univ State Key Lab Precis Measurement Technol & Instru Dept Precis Instruments Beijing 100084 Peoples R China

We summarize some design tips and design procedures of nanoapertures with strong field enhancement, based on the theoretical calculations and analyses of near-field distributions of unconventional C apertures and bow-tie apertures by a finite-difference time-domain method. A novel L-shaped aperture is proposed and further validates the proposed design rule. As a result, a 15x15-nm full width half maximum spot forms in the light exit plane of the L aperture. Its intensity maximum enhancement reaches a factor of about 568 and the power throughput is bigger than unity. The mechanisms of electromagnetic field enhancement are preliminarily analyzed. This unconventional nanoaperture is likely to be directly used as an exit aperture of very small aperture lasers, or as an unattached shield, to produce a subwavelength light source with high transmission. (C) 2005 Society of Photo-Optical Instrumentation Engineers.

关键词： near-field optics nanoaperture field enhancement finite-difference time-domain method

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A separation of the refractive index and topography in photon-scanning tunneling microscopy: Simulations and experiments

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ULTRAMICROSCOPY 2005年第1期104卷 1-7页

作者： Wang, XQ Zhang, J Li, YL Jian, GS Suen, W Pan, S Wu, S Dalian Univ Technol Dept Phys Dalian 116024 Peoples R China Dalian Univ Technol Dept Phys Dalian 116622 Peoples R China

In order to separate the purely optical and topographic information from images in constant-gap mode simultaneously, we proposed the atomic force/photon-scanning tunneling microscopy (AF/PSTM). In this paper, we focus on the principle of separation of the refractive index image from the images of photon-scanning tunneling microscopy. We prove the formula of refractive index imaging by using a three-dimensional finite-difference time-domain method. The formula indicates that the refractive index of a sample is approximately proportional to photon tunneling information (Delta I/(I) over bar)(2). From the viewpoint of practical use, we simulated the refractive index images for the realistic experiments. We present line scans along two orthogonal directions and the transmitted intensity as a function of the tip position under the constant-Gap mode. The experimental results are presented and are in good agreement with the numerical results. (c) 2005 Published by Elsevier B.V.

关键词： refractive index image topography finite-difference time-domain method AF/PSTM

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Band structure calculation in two-dimensional Kerr-nonlinear photonic crystals

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OPTICS COMMUNICATIONS 2005年第4-6期248卷 469-477页

作者： Maksymov, IS Marsal, LF Ustyantsev, MA Pallarès, J Univ Rovira & Virgili Dept Elect Engn Tarragona 43007 Spain

Using the finite-difference time-domain method, based on the numerical simulation of oscillating dipole radiation, we analyze band structures in two-dimensional Kerr-nonlinear photonic crystals. This method is more thorough at calculating band structures in two-dimensional Kerr-nonlinear photonic crystals than approaches proposed earlier. We find that the band structures calculated for both TE and TM polarizations are dynamically red-shifted with regard to the linear case. For a positive Kerr coefficient, this red-shift increases as the intensity of the oscillating dipole increases. (c) 2004 Elsevier B.V. All rights reserved.

关键词： two-dimensional nonlinear photonic crystal finite-difference time-domain method oscillating dipole band structure Kerr coefficient dynamic red-shift

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Analysis of excitations for a groove guide resonator at 10 GHz by means of the FDTD method

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INTERNATIONAL JOURNAL OF INFRARED AND MILLIMETER WAVES 2005年第6期26卷 819-830页

作者： Bechteler, TF Izmir Inst Technol Dept Elect & Elect Engn TR-35430 Urla Izmir Turkey

Various excitations of a new groove guide resonator working in the X-band (8 GHz - 12 GHz) are investigated by means of numerical simulations. For the numerical simulations the finite-difference time-domain method is used. The groove guide resonator, modelled both with and without excitation structures, is discretised in space. The results in the time domain are then transformed into the frequency domain in order to obtain the resonance frequency spectrum. Comparison between simulations with and without excitations shows the effect of the excitations on the resonance frequency spectrum. The results are compared with those of previous analytical methods.

关键词： groove guide resonator finite-difference time-domain method excitation millimeter waves

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Enhanced resolution induced by random silver nanoparticles in near-field optical disks

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OPTICS COMMUNICATIONS 2005年第4-6期246卷 561-567页

作者： Chu, TC Liu, WC Tsai, DP Natl Taiwan Univ Ctr Nanostorage Res Taipei 11676 Taiwan Natl Taiwan Univ Dept Phys Taipei 11676 Taiwan Natl Taiwan Normal Univ Dept Phys Taipei 11676 Taiwan

The super-resolution near-field structure (super-RENS) is a high-density near-field optical data storage medium which can achieve superior spatial resolution beyond the diffraction limit. Our previous studies found that enhanced local optical intensity occurred at the near fields of super-RENS disks, and the nonlinear near-field optical enhancement is related to the localized surface plasmons of silver clusters dissociated from the AgOx layer in the super-RENS disks. In this paper, we studied the near-field and far-field properties of AgOx-type super-RENS with different distributions of silver nanoparticles using finite-difference time-domain (FDTD) simulations. Highly localized enhancements are found between adjacent silver nanoparticles in the near fields. The far-field signals of different silver nanoparticles distributions confirm the super-resolution capability of AgOx-type Super-RENS disks, and a simplified Fourier optics model is used to describe the relation between highly localized near-field distributions and enhanced resolution of far-field signals. (C) 2004 Elsevier B.V. All rights reserved.

关键词： localized surface plasmon super-resolution near-field structure high-density optical disks near-field optical storage optical disks finite-difference time-domain method

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3D low-dispersion ifd-fdtd based on 3D isotropic finite difference

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MICROWAVE AND OPTICAL TECHNOLOGY LETTERS 2005年第4期46卷 381-384页

作者： Xiao, F Tang, XH Mao, RJ Zhang, XJ UESTC Sch Elect Engn Chengdu Peoples R China

Usually, ID finite difference based on the Taylor series expansion theorem is used to approximate the spatial ideal partial-differential operator (IPDO) using conventional FDTD methods. Such a treatment is simple, but its severe numerical dispersion is untenable. In this paper, a kind of 3D isotropic finite difference (IFD) is introduced and a new FDTD method, called IFD-FDTD, is presented. A numerical-dispersion analysis shows that it is superior to Yee's conventional FDTD method. In addition, through the analysis of stability, it is found that its stability, condition is the same as that of Yee's FDTD method. (c) 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 381-384, 2005;Published online in Wiley InterScience (***). DOI 10.1002/mop.20993.

关键词： 3D isotropic finite difference finite-difference time-domain method numerical dispersion

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High-Q microcavities realized in a circular photonic crystal slab

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PHOTONICS AND NANOSTRUCTURES-FUNDAMENTALS AND APPLICATIONS 2005年第2-3期3卷 134-138页

作者： Xiao, SS Qiu, M Royal Inst Technol Dept Microelect & Informat Technol Lab Opt Photon & Quantum Elect S-16440 Stockholm Sweden

A series of microcavities in circular photonic crystal slabs are studied in this paper. It is shown that high quality factors can be obtained for such microcavities. For a cavity with three inner layers of air holes missing, Q factor larger than 105 can be obtained. It is also worth noting there exists resonant modes with high quality factors, even for the defect-free circular photonic crystal slab, due to gradual change of the average effective index. (c) 2005 Elsevier B.V. All rights reserved.

关键词： microcavity photonic crystal finite-difference time-domain method

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