• Title/Summary/Keyword: Finite-difference time-domain simulations

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Generation of Non-uniform Meshes for Finite-Difference Time-Domain Simulations

  • Kim, Hyeong-Seok;Ihm, In-Sung;Choi, Kyung
    • Journal of Electrical Engineering and Technology
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    • v.6 no.1
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    • pp.128-132
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    • 2011
  • In this paper, two automatic mesh generation algorithms are presented. The methods seek to optimize mesh density with regard to geometries exhibiting both fine and coarse physical structures. When generating meshes, the algorithms attempt to satisfy the conditions on the maximum mesh spacing and the maximum grading ratio simultaneously. Both algorithms successfully produce non-uniform meshes that satisfy the requirements for finite-difference time-domain simulations of microwave components. Additionally, an algorithm successfully generates a minimum number of grid points while maintaining the simulation accuracy.

Radio wave propagation simulations of indoor by finite difference time domain method (실내 전파 차분의 시간영역 유한차분법에 의한 계산)

  • 허문만;백낙준;박항구;윤현보
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.34D no.10
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    • pp.60-67
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    • 1997
  • This paper presents a 3-D finite difference time domain (FDTD) method used for indoor propagation simulations where the electromagnetic wav eis uniformly excited on th eone of the wall in a building and affected by an indoor obstacles. In cases of simulation and measurement, the frequency of 851 MHz is used. The conductivities of walls, floor, ceiling and indoor obstacles are measured and used for simulations. These simulations are carried out using different boundary condition such as mur's absorbing boundary condition (ABC) and perfectly matched layer (PML) technique. The PML technique is found to be well-suited to this analysis because of it's smaller computational domain than mur's ABC. The measured signal strengths are compared to simulated values with good agreement.

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Developing a simulator for Super-RENS/ROM disk using finite difference time domain method (Super-ROM/RENS 디스크 구조의 재생신호 해석을 위한 유한차분 시간구역 (FDTD) 방법을 이용한 시뮬레이터 개발)

  • Ahn Duck-Won;You Chun-Yeol
    • 정보저장시스템학회:학술대회논문집
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    • 2005.10a
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    • pp.32-37
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    • 2005
  • We developed a numerical simulator in order to study the Super-RENS/ROM (Super REsolution Near-Field Structure, Read Only Memory) using 3-dimensional FDTD (finite difference time domain) method. The simulation can be performed by three steps. In the first step, we utilized the vector-diffraction theory to calculate the characteristics of incident laser beam from the object-lens to the surface of the disk. At the second step, we fed the calculated result as an input for the main FDTD simulations on the optical layers in the disk structure. After performed the FDTD simulations, we took near-to-far field transformation for the reflected signal, from the surface of the disk to the detector. Finally, we can get reflected signal at the photo-diode. Using this developed simulator, we were able to study about the reading signal from various disk structures as a function of a laser beam position. We calculated reading signals for various pit sizes for Super-ROM structure, and it is found that the simple optical diffraction theory can not explain the reading mechanism of Super-ROM, and more complicated temperature dependent physics must be involved.

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Developing a simulator for Super-RENS/ROM disk using finite difference time domain method (Super-ROM/RENS 디스크 구조의 재생신호 해석을 위한 유한차분시간구역 (FDTD) 방법을 이용한 시뮬레이터 개발)

  • Ahn, Duck-Won;You, Chun-Yeol
    • Transactions of the Society of Information Storage Systems
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    • v.2 no.2
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    • pp.138-143
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    • 2006
  • We developed a numerical simulator in order to study the Super-RENS/ROM (Super REsolution Near-Field Structure, Read Only Memory) using 3-dimensional FDTD (finite difference time domain) method. The simulation can be performed by three steps. In the first step, we utilized the vector-diffraction theory to calculate the characteristics of incident laser beam from the object-lens to the surface of the disk. At the second step, we fed the calculated result as an input for the main FDTD simulations on the optical layers in the disk structure. After performed the FDTD simulations, we took near-to-far field transformation for the reflected signal, from the surface of the disk to the detector. Finally, we can get reflected signal at the photo-diode. Using this developed simulator, we were able to study about the reading signal from various disk structures as a function of a laser beam position. We calculated reading signals for various pit sizes for Super-ROM structure, and it is found that the simple optical diffraction theory can not explain the reading mechanism of Super-ROM, and more complicated temperature dependent physics must be involved.

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Numerical Simulation of Ground-Penetrating Radar Signals for Detection of Metal Pipes Buried in Inhomogeneous Grounds (비균일 지하에 매설된 금속관 탐지를 위한 지하탐사레이다 신호의 수치 모의계산)

  • Hyun, Seung-Yeup
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.1
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    • pp.61-67
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    • 2018
  • The effects of subsurface inhomogeneities on the detection of buried metal pipes in ground-penetrating radar(GPR) signals are investigated numerically. To model the electrical properties of the subsurface inhomogeneities, the continuous random media(CRM) generation technique is introduced. For the electromagnetic simulation of GPR signals, the finite-difference time-domain(FDTD) method is implemented. As a function of the standard deviation and the correlation length of the relative permittivity distribution for a randomly inhomogeneous ground, the GPR signals of the buried metal pipes are compared using numerical simulations. As the subsurface inhomogeneities increase, the GPR signals of the buried pipes are distorted because of the effect of the subsurface clutter.

Simulations of Transmittance for the ITO/Ag/ITO Multiple Transparent Electrode Layers by 3 Dimensional FDTD Method (3차원 FDTD 방법에 의한 ITO/Ag/ITO 다층 투명전극막의 투과도 시뮬레이션)

  • Kim, Ki Rak;Cho, Eou Sik;Kwon, Sang Jik
    • Journal of the Semiconductor & Display Technology
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    • v.19 no.3
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    • pp.88-92
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    • 2020
  • As a highly conductive and transparent electrode, the optical transmittances of ITO/Ag/ITO were simulated and compared with the experimental results. The simulations are based on the finite-difference time-domain (FDTD) method in solving linear Maxwell equations. In our simulations, the computation domain is set in the XZ-plane with 3D dimension, and a plane wave with variable wavelengths ranging from 250 nm to 850 nm is incident in the z-direction at normal incidence to the ITO/Ag/ITO film surrounded by free-air space. As the results through both simulations and experiments, it was shown that the thickness combinations by the ITO layers of about 40 nm and the Ag layer of about 10 nm could be most suitable conditions as a high conductive transparent electrode having the transmittance similar to that of a single ITO layer.

A Fourth-Order Accurate Numerical Boundary Scheme for the Planar Dielectric Interface: a 2-D TM Case

  • Hwang, Kyu-Pyung
    • Journal of electromagnetic engineering and science
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    • v.11 no.1
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    • pp.11-15
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    • 2011
  • Preserving high-order accuracy in high-order FDTD solutions across dielectric interfaces is very important for practical time-domain electromagnetic simulations. This paper presents a fourth-order accurate numerical boundary scheme for the planar dielectric interface to be used in the fourth-order FDTD method proposed earlier by the author. The interface scheme for the two-dimensional (2-D) transverse magnetic (TM) polarization case is derived and validated by monitoring the $L_2$ norm errors in the numerical solutions of a partially-filled cavity demonstrating its fourth-order convergence and long-time numerical stability in the presence of the planar dielectric interface.

Resonance Characteristics of THz Metamaterials Based on a Drude Metal with Finite Permittivity

  • Jun, Seung Won;Ahn, Yeong Hwan
    • Current Optics and Photonics
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    • v.2 no.4
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    • pp.378-382
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    • 2018
  • In most previous investigations of plasmonic and metamaterial applications, the metallic film has been regarded as a perfect electrical conductor. Here we demonstrate the resonance characteristics of THz metamaterials fabricated from metal film that has a finite dielectric constant, using finite-difference time-domain simulations. We found strong redshift and spectral broadening of the resonance as we decrease the metal's plasma frequency in the Drude free-electron model. The frequency shift can be attributed to the effective thinning of the metal film, originating from the increase in penetration depth as the plasma frequency decreases. On the contrary, only peak broadening occurs with an increase in the scattering rate. The metal-thickness dependence confirms that the redshift and spectral broadening occur when the effective metal thickness drops below the skin-depth limit. The electromagnetic field distribution illustrates the reduced field enhancement and reduced funneling effects near the gap area in the case of low plasma frequency, which is associated with reduced charge density in the metal film.

A Comparison between EFIU and HEIU Schemes in ADI-FDTD Simulations (ADI-FDTD 해석에서의 EFIU와 HFIU 계산 방법 비교 연구)

  • Ju Sae-Hoon;Lee Kyung-Hoon;Hwang In-Ho;Kim Hyeong-Dong
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.1 s.104
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    • pp.8-16
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    • 2006
  • In this paper, updating schemes for the alternating-direction implicit finite-difference time-domain method(ADI-FDTD) are studied, which method has the potential to considerably reduce the number of time iterations especially in case where the fine spatial lattice relative to the wavelength is used to resolve fine geometrical features. In numerical simulations for microwave structure using ADI-FDTD, time marching scheme comprises of two sub-iterations. Two different updating equation sets for ADI-FDTD simulations are presented. In order to discuss the characteristics of those schemes especially in view of applying boundary conditions, we solved two complementary 2-D problems.

Dependence of Q Factor on Surface Roughness in a Plasmonic Cavity

  • Kim, Yoon-Ho;Kwon, Soon-Hong;Ee, Ho-Seok;Hwang, Yongsop;No, You-Shin;Park, Hong-Gyu
    • Journal of the Optical Society of Korea
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    • v.20 no.1
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    • pp.188-191
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    • 2016
  • We investigated surface-roughness-dependent optical loss in a plasmonic cavity consisting of a semiconductor nanodisk/silver nanopan structure. Numerical simulations show that the quality factors of plasmonic resonant modes significantly depend on the surface roughness of the dielectric-metal interface in the cavity structure. In the transverse-magnetic-like whispering-gallery plasmonic mode excited in a structure with disk diameter of 1000 nm, the total quality factor decreased from 260 to 130 with increasing root-mean-square (rms) surface roughness from 0 to 5 nm. This quantitative theoretical study shows that the smooth metal surface plays a critical role in high-performance plasmonic devices.