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170 results on '"Jung, Kyung-Young"'

14. FDTD Modeling for the Accurate Electromagnetic Wave Analysis of Graphene

Author

Kim, Yeon-Hwa, Choi, Hongjin, Cho, Jeahoon, and Jung, Kyung-Young

Abstract

We develop a finite-difference time-domain (FDTD) method suitable for the electromagnetic (EM) analysis of graphene. In this work, we employ the modified Lorentz model for dispersion modeling, the two-dimensional (2-D) sheet model for geometrical modeling, and the complex-frequency-shifted (CFS)-perfectly matched layer (PML) for the absorbing boundary condition. In specific, the accurate complex-conjugate pole-residue (CCPR) dispersion model is first adapted for the electrical modeling of graphene by using the robust vector fitting. Next, the CCPR parameters are converted to the modified Lorentz parameters and then the modified Lorentz-based dispersive FDTD formulation is used to enhance the computational efficiency. In FDTD cell modeling, the 2-D sheet cells are allocated for graphene rather than the conventional FDTD cell-based modeling. Finally, CFS-PML are employed for terminating the computational domain to avoid the late-time instability. The presented FDTD approach is validated in numerical examples for graphene-based parallel plate waveguides.

Published
2024
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27. On numerical artifacts of the complex envelope ADI-FDTD method

Author

Jung, Kyung-Young, Teixeira, Fernando L., Garcia, Salvador G., and Lee, Robert

Subjects
Simulation methods -- Analysis, Radiation -- Analysis, Business, Computers, Electronics, Electronics and electrical industries
Abstract

We examine two spurious numerical artifacts of the complex envelope (CE) alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method, viz. spurious charges and anomalous wave propagation (modes with positive phase velocity and negative group velocity). These artifacts are also present in the conventional ADI-FDTD; however, the spurious charges in CE-ADI-FDTD have a fundamental distinction from those of ADI-FDTD: they are static in ADI-FDTD and implicitly time-harmonic in CE-ADI-FDTD. Spurious charges are particularly detrimental to CE-ADI-FDTD simulations because they produce secondary radiation. We also show that spurious charges can be reduced by a fixed-point iterative correction in CE-ADI-FDTD. Index Terms--Alternating-direction-implicit finite-difference time-domain (ADI-FDTD), complex envelope (CE), divergence, spurious mode.

Published
2009

28. Frozen modes in parallel-plate waveguides loaded with magnetic photonic crystals

Author

Chilton, Ryan A., Jung, Kyung-Young, Lee, Robert, and Teixeira, Fernando L.

Subjects
Waveguides -- Design and construction, Photonics -- Research, Electromagnetism -- Research, Business, Computers, Electronics, Electronics and electrical industries
Abstract

We examine parallel-plate magnetic photonic crystal (MPC) waveguides comprised of a periodic loading with two anisotropic layers and one ferrite layer on each period. It is shown that, at a specific design frequency [f.sub.o], parallel-plate MPC waveguides can support a Bluch mode with zero axial group velocity similar to the 'frozen mode' regime of the prototypical I-D MPC structure. When the proposed 2-D structure is illuminated with a properly polarized time-harmonic wave, near unity power transmission (coupling) into the frozen mode occurs, and field strength within the MPC becomes orders of magnitude larger than the incident field strength. The steady-state case is evaluated using both analytical tools and finite elements, while the finite-difference time-domain method is applied to evaluate the 2-D MPC transient response. Index Terms--Dispersion engineering, frozen mode, guidedwave propagation, magnetic photonic crystals (MPCs), numerical techniques in electromagnetics.

Published
2007

47. Design of a four‐element array for accurate direction of arrival estimation in phase interferometry systems.

Author

Yoo, Sungjun, Byun, Gangil, Park, Seulgi, Ju, Hyungjun, Shim, Hongsuk, Chae, Myoungho, Jung, Kyung‐Young, and Choo, Hosung

Subjects
DIRECTION of arrival estimation, PHASED array antennas, PHASE-shifting interferometry, GLOBAL Positioning System, ANTENNA arrays, INTERFEROMETRY, LOW Temperature Cofired Ceramic technology, CURRENT distribution
Abstract

This article proposes the design of a four‐element array antenna for the accurate direction of arrival (DOA) estimation of Global Positioning System (GPS) interference signals. The proposed array antenna has four individual antenna elements, and each element consists of a radiating patch on the upper layer and a feeding loop on the lower layer. The patch and loop are intentionally designed in a circular shape to obtain the symmetric current distributions on the radiators. The feeding loop is directly connected by two output ports of an external hybrid chip coupler, and the radiating patch is then electromagnetically coupled by near‐fields of the feeding loop. This feeding mechanism in the proposed structure allows for a more uniform current and H‐field distribution for phase characteristics of the radiation that are close to the ideal isotropic radiators in the azimuth angle. In addition, the high‐dielectric ceramic substrate is adopted to minimize the physical height of the antenna for the phase characteristics of the radiation close to the ideal isotropic radiators in elevation angles. To validate that the phase characteristics are similar to those of an ideal radiator, the DOA estimation performances are observed using a dual‐axis interferometry. The results demonstrate that the proposed four‐element array antenna with phase difference characteristics similar to those of an ideal radiator is suitable for the accurate DOA estimation of GPS interference signals. [ABSTRACT FROM AUTHOR]

Published
2020
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