• ETRI Journal
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• v.46 no.2
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• pp.333-346
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• 2024

Various techniques for noninvasively focus microwave energy on lesions have been proposed for thermotherapy. To focus the microwave energy on the lesion, a focusing parameter, which is referred to as the magnitude and phase of microwaves radiated from an external array antenna, is very important. Although the finite-difference time-domain (FDTD)-based time-reversal (TR) focusing algorithm is widely used, it has a long processing time if the focusing target position changes or if optimization is needed. We propose a technique to obtain multistatic data (MSD) based on Green's function and use it to derive the focusing parameters. Computer simulations were used to evaluate the electric fields inside the object using the FDTD method and Green's function as well as to compare the focusing parameters using FDTD- and MSD-based TR focusing algorithms. Regardless of the use of Green's function, the processing time of MSD-based TR focusing algorithms reduces to approximately 1/2 or 1/590 compared with the FDTD-based algorithm. In addition, we optimize the focusing parameters to eliminate hotspots, which are unnecessary focusing positions, by adding phase-reversed electric fields and confirm hotspot suppression through simulations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.42-48
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• 2017

Characteristics of ground-penetrating radar(GPR) signals for detecting buried pipes are investigated numerically. Transmitting and receiving parts of a GPR system, a subsurface soil and a plastic pipe filled with a dielectric material are modeled by using the finite-difference time-domain(FDTD) method. FDTD simulations for observing aspects of GPR signals are performed as a function of the diameter of the pipe and the permittivity of the filling material in the pipe. GPR signals scattered by a dielectric filled pipe appear as a superposition of two waves, such as the specular wave from the front convex surface of the pipe and the axial wave from the rear concave surface of the pipe. We show that the amplitude, the polarity, the delay time of two waves depend on the size of the pipe and the permittivity of the filling material in the pipe.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.276-279
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• 2015

This paper propose a method to reduce the backscatter field of the curved aluminum plate using the cancellation system. The cancellation circuit is composed of a circulator, a LNA(Low Noise Amplifier), a VGA(Variable Gain Amplifier) and two phase shifters. Prior to experiment, we performed simulations to confirm the possibility using FDTD(Finite Difference Time Domain) simulator. We confirmed that the backscatter field could be reduced by the cancellation circuit when we changed the appropriate gain and phase. Finally, we performed an experiment to verify the performance of the cancellation circuit.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.1
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• pp.55-61
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• 2003

This paper describes how the optical properties of a quasi-one-dimensional photonic crystalline waveguide having a periodic air cavity are influenced by various structural parameters; the electromagnetic fields are simulated using the finite-difference time-domain method. The simulations considered four design parameters: cavity size, defect size, lattice constant, and number of cavity. The parameter sensitivity of the photonic bandgap property of the waveguide having air cavities is examined. A couple of significant design guidelines are obtained. We show that the quasi-one-dimensional photonic crystalline waveguide has significant unrealized potential.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.340-343
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• 2002

Electromagnetic(EM) radiation problems and their possible solutions are addressed in this paper for the split power plane of high-speed digital systems. Stitching and decoupling capacitors are proved to be very effective fur reducing signal noise, ground bounce as well as electromagnetic radiation from the split power plane. Simulations based on 3D-Finite Difference Time Domain (FDTD) method are utilized for the analysis of practical high frequency multi-layered PC main board

• Current Optics and Photonics
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• v.1 no.6
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• pp.637-641
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• 2017

We present dielectric constant measurements of thin films using THz metamaterials fabricated on a quartz substrate. The resonance shifts of the metamaterials exhibit saturation behavior with increasing film thickness. The saturation frequency shift varies with the real part of the dielectric constant, from which the numerical expression for the particular metamaterial design was extracted. We first performed finite-difference time-domain simulations to find an explicit relationship between the saturated frequency shift and the dielectric constant of a thin film, which was confirmed by the experimental results from conventional techniques. In particular, the quartz substrate enables us to determine their values more accurately, because of its low substrate index. As a result, we extracted the dielectric constants of various films whose values have not been addressed previously without precise control of the film thickness.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.197.1-197.1
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• 2014

VO2 has intensively investigated for several decades due to its interesting physical properties, including metal-insulator transition (MIT), thermochromic and thermoelectric properties, near the room temperature. And also gas and photo sensing properties of VO2 nanowires have attracted increasing research interest due to the high sensitivity and multi-sensing capability. We studied the light-induced resistance change of VO2 nanowires. In particular, we have investigated plasmonic enhancement of the photo-sensing properties of the VO2 nanowires. To select proper wavelength, we performed finite-difference time-domain simulations of electric field distribution in the VO2 nanowires attached with Ag nanoparticles. Localized surface plasmon resonance (LSPR) is expected at wavelength of 560 nm. The photo-sensitivity was carefully examined as a function of the sample temperature. In the presentation, we will discuss physical origins of the photo-induced resistance change in VO2.

• Journal of electromagnetic engineering and science
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• v.2 no.2
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• pp.75-80
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• 2002

Signal integrity problems and their possible solutions are addressed in this paper for split power plane of high-speed digital systems. Stitching and decoupling capacitors are proved to be very effective for reducing signal noise, ground bounce as well as electromagnetic radiation from the split power plane. Simulations based on 3D-Finite Difference Time Domain (FDTD) method are utilized for the analysis of practical high frequency multi-layered PC main board.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.533-540
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• 1999

In this paper, a microstrip antenna is designed using a rectangular patch. To find characteristics of the antenna, computer simulations of the rectangular single microstrip patch antenna are performed with changing width and feed line. And we found characteristics of RHCP using axial ratio. Through the results, we found that the Finite Difference Time Domain(FDTD) method is an effective method for designing microstrip patch antenna. According to simulation the resonant point has been found it in the frequency received from GPS satellite. And these results were in relatively good accordance with the measured values.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.87-91
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• 2019

As a highly conductive and transparent electrode, ITO/Ag/ITO multilayers are fabricated using an in-line sputtering method. Optimal thickness conditions have been investigated in terms of the optical transmittance and the electrical conductance. Considering the optical properties, in this study, the experimental characteristics are analyzed based on theoretical phenomena, and they are compared with the simulated results. The simulations are based on the finite-difference-time-domain (FDTD) method in solving linear Maxwell equations. Consequently, the results showed that ITO/Ag/ITO multilayer structures with respective thicknesses of 39.2 nm/10.7 nm/39.2 nm are most suitable with an average transmittance of about 87% calculated for wavelengths ranging from 400-800 nm and a sheet resistance of about $7.1{\Omega}/{\square}$.