유한차분 시간영역법 전자파 해석 기술

조제훈,정경영 한국전자파학회 2017 전자파기술 Vol.28 No.6

Numerical Accuracy of Finite-Difference Time-Domain Formulations for Magnetized Plasma

조제훈,박민석,정경영 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.3

The finite-difference time-domain (FDTD) has been widely used to analyze electromagnetic (EM) wave propagation in complex dispersive media. Over the past three decades, a variety of FDTD approaches for the EM wave propagation in magnetized plasma has been presented. In this work, we perform a comprehensive study on the numerical accuracy of four FDTD formulations for magnetized plasma including the JE convolution (JEC) method, the exponential time differencing (ETD) method, the H-J collocated auxiliary differential equation (ADE) method, and the E-J collocated ADE method. Toward this purpose, the numerical permittivity tensor of magnetized plasma in the four FDTD formulations are derived and then we analyze them to determine which approach can provide the best accuracy. It is found that the E-J collocated ADE method can lead to the best accuracy. Numerical examples awere performed to validate our investigations.

FDTD 방법을 이용한 간단한 건물 구조의 광대역 차폐 효과에 관한 연구

조제훈(Jeahoon Cho),하상규(Sang-Gyu Ha),박성민(Sungmin Park),추광욱(Kwanguk Chu),주세훈(Saehoon Ju),김형동(Hyeongdong Kim),정경영(Kyung-Young Jung) 한국전자파학회 2013 한국전자파학회논문지 Vol.24 No.7

본 논문은 유한 차분 시간 영역(FDTD: Finite-Difference Time-Domain)법을 이용하여 간단한 건물 구조의 광대역 복사성 펄스 결합에 관한 연구를 수행하였다. 이를 위해 건물을 콘크리트와 유리로 구성하였으며, 각 물질의 전기적 특성을 수치적으로 모델링하였다. 본 논문에서는 본 연구팀에서 개발한 분산 FDTD 알고리즘을 이용하여 건물의 전자파 특성 해석을 수행하고, 건물 구조에 따른 차폐 효과를 50 MHz~1 GHz 대역에서 분석하였다. We perform a wideband radiated pulse coupling analysis of simple building structures using the finite-deference time-domain(FDTD) method. Toward this purpose, the building structures composed of concrete and window materials are assumed and we numerically model the electrical properties of each material. In this work, we apply a dispersive FDTD algorithm for the electromagnetic analysis of building structures and investigate their shielding effectiveness in the frequency range of 50 MHz to 1 GHz.

낙뢰에 노출된 높은 도전성 구조체의 간접적 영향 분석을 위한 전자파 해석기법 연구

조제훈(Jeahoon Cho),이진호(Jinho Lee),태현성(Hyun-Sung Tae),정경영(Kyung-Young Jung) 한국전자파학회 2016 한국전자파학회논문지 Vol.27 No.11

본 논문은 유한 차분 시간 영역(FDTD: Finite-Difference Time-Domain)법을 이용하여 낙뢰에 노출된 항공기와 같이 높은 도전성 물질로 구성된 구조체의 간접적 영향 분석을 위한 전자파 해석기법 연구를 수행하였다. 간접적 영향 분석을 위해 사용되는 낙뢰 파형은 매우 낮은 주파수 특성을 가지며, 알루미늄과 탄소섬유복합물질과 같이 높은 도전성 물질들로 구성된 구조체는 매우 짧은 표피 깊이를 가지고 있기 때문에 일반적인 3차원 FDTD법을 이용하여 해석을 수행할 경우, 매우 많은 메모리와 해석시간이 요구된다. 본 연구팀에서는 낙뢰 특성과 높은 도전율을 갖는 구조에 적합한 전자파해석기법을 개발하였다. 개발된 해석 기법은 2차원 FDTD와 INBC(Impedance Network Boundary Condition) 알고리즘을 적용하였으며, 개발된 해석기법을 이용하여 낙뢰에 노출된 구조체의 간접적 영향을 분석하였다. We perform a electromagnetic analysis method for indirect effects of a high-conductive structure such as an aircraft exposed by lightning, by using the finite-difference time-domain(FDTD) method. The lightning waveform used to analyze indirect effects has low frequency spectrum and high-conductive materials such as aluminum and carbon fiber composite materials have very short skin depths, and thus, it requires large memory and long computation time using conventional three dimensional FDTD analysis method. We develop an efficient electromagnetic analysis method suitable for lightning and high-conductive structures. The developed analysis method is based on two dimensional FDTD and impedance network boundary condition(INBC) algorithms and we investigate the indirect effects on the structures exposed to lightning.

LGU+ 관점에서 보는 차세대 이동통신 네트워크

조제훈(Jehoon Cho),윤규섭(Kyuseop Yoon),이상헌(Sangheon Lee) 한국정보과학회 2023 정보과학회지 Vol.41 No.10

Chain Matrix를 이용한 Twisted Cable의 EMP(Electromagnetic Pulse) 결합 해석

조제훈(Jeahoon Cho),이진호(Jinho Lee),김형동(Hyeongdong Kim) 한국전자파학회 2010 한국전자파학회논문지 Vol.21 No.7

본 논문은 다중 도체 전송선 해석법과 chain matrix 알고리즘을 이용하여 twisted cable과 같은 비균일 전송선의 EMP 결합을 해석하였다. 전송선의 EMP 결합 해석을 위해 BLT(Baum-Liu-Tesche) 해석법이 널리 사용되고 있으나, twisted cable과 같은 비균일 전송선에 기존의 BLT 해석법을 바로 적용하기는 어렵다. Twisted cable과 같은 비균일 전송선을 해석하기 위해 수많은 작은 길이의 균일 전송선으로 나누어 모델링하였으며, 전체 비균일 전송선의 결합 특성은 각각의 균일 전송선의 EMP 결합 분석을 통해 최종적인 전송선의 결합 특성을 구함으로써 가능해진다. 이러한 비균일 전송선 EMP 결합 해석 기법을 검증하기 위해 균일 전송선에 대하여 기존의 BLT 해석 결과와 비교하였으며, 제시된 비균일 전송선 EMP 결합 해석 기법을 지표면 위에 놓여 있는 twisted cable에 적용하여 대기 중의 핵폭발에 의한 HEMP(High altitude Electromagnetic Pulse)와 같은 매우 강한 펄스가 입사되었을 때, 전송선에 연결된 부하에 유기되는 전류(또는 전압) 응답을 분석하였다. In this paper, we analyzed the EMP coupling for the nonuniform transmission lines, such as twisted cables, using the chain matrix algorithm and the multi-conductor analysis. The BLT method is widely used for the EMP coupling analysis of the transmission line, however, it is difficult to apply to the nonuniform transmission lines. In order to analyze the EMP coupling of nonuniform transmission lines, the whole nonuniform transmission line is divided into incremental uniform line sections of the finite numbers, and the coupling in each small sections is now summed up to get the EMP coupling effect of the entire nonuniform transmission line. To verify the proposed EMP coupling analysis method, the result of the EMP coupling simulation is compared with the solution of BLT equations for a uniform transmission line case. The proposed method is applied to the twisted cable over ground in case of being illuminated by the HEMP in order to analyze the EMP coupling.

Efficient Finite-Difference Time-Domain Modeling of Time-Varying Dusty Plasma

김용진,조제훈,정경영 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.4

The finite-difference time-domain (FDTD) method has been widely used for the electromagnetic analysis of dusty plasma sheath in re- entering hypersonic vehicles. The time-varying characteristics of dusty plasma should be considered to accurately analyze THz wave propaga- tion in dusty plasma. In this work, we propose an efficient FDTD modeling of time-varying dusty plasma based on the combination of the bilinear transform and the state-space approach. The proposed FDTD formulation for time-varying dusty plasma can lead to a significant improvement in computational efficiency against the conventional shift operator FDTD counterpart while maintaining numerical accuracy. Numerical examples are performed to validate the proposed FDTD modeling of time-varying dusty plasma.

New Measurement Technique for Complex Permittivity in Millimeter-Wave Band Using Simple Rectangular Waveguide Adapters

박민석,조제훈,이순용,권영근,정경영 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.6

This research presents a novel methodology for measuring the complex permittivity of a material under test (MUT) in a millimeter-wave (mmWave) band by using two rectangular waveguide adapters. Contrary to the conventional Nicolson-Ross-Weir (NRW) method, the proposed complex permittivity measurement method does not require a material fabrication process for exact MUT insertion into a waveguide. In our complex permittivity measurement, simple commercial waveguide adapters are employed instead of large flange structures. The proposed complex permittivity measurement of a non-destructive MUT is achieved by combining the NRW method, the Gaussian weighting moving average filtering technique, a full-wave electromagnetic analysis, and an optimization technique. Furthermore, the proposed methodology is validated by fabricating a Teflon-based MUT and by measuring the complex permittivity of the MUT in the Ka band (26.5–40 GHz). The results indicate that the proposed methodology exhibits good agreement with the data sheet.

변형된 접지면 구조를 이용한 대역폭 확장 특성을 갖는 보우-타이형 준-야기 안테나

이지수,조제훈,최재훈,정경영 한국전자파학회 2023 한국전자파학회논문지 Vol.34 No.2

In this paper, a bow-tie quasi-Yagi antenna with a modified ground plane structure is proposed for wideband characteristics. The ground plane structure of the proposed antenna improved the impedance-matching characteristics by inserting a parallel plate ground with a width equal to the parallel-coupled feed line width. This simply modified ground plane structure can lead to an improvement in impedance matching by additional inductance, capacitance, mutual inductance, and mutual capacitance components. The proposed antenna has a −10-dB reflection coefficient fractional bandwidth of 30 % and a realized gain of 7.7 dBi at the center frequency.

Accurate FDTD Dispersive Modeling for Concrete Materials

장해준,조제훈,하상규,주세훈,정경영 한국전자통신연구원 2013 ETRI Journal Vol.35 No.5

This work presents an accurate finite-difference time-domain (FDTD) dispersive modeling of concrete materials with different water/cement ratios in 50 MHz to 1 GHz. A quadratic complex rational function (QCRF) is employed for dispersive modeling of the relative permittivity of concrete materials. To improve the curve fitting of the QCRF model, the Newton iterative method is applied to determine a weighting factor. Numerical examples validate the accuracy of the proposed dispersive FDTD modeling.