• 한국전자파학회논문지
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• 제26권10호
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• pp.907-913
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• 2015

본 논문은 회로 시뮬레이션과 전자기 시뮬레이션을 병행하여 디지털 스위칭 회로가 실장된 PCB 상의 근접 자계 분포를 예측하는 방법을 제시한다. 제안 방법은 스위칭 회로의 신호 및 전원 포트를 정현 전원으로 구동하여 규격화된 근접 자계 분포를 구하고, 이 결과를 실제 스위칭 회로에 의한 전류의 주파수 스펙트럼으로 가중하여 근접 자계를 예측한다. 예측 방법론을 검증하기 위해 링 발진기와 출력 버퍼로 구성된 스위칭 집적 회로를 제작하고, 칩-온-보드(Chip On Board, 칩-온-보드) 형태로 평가하였다. 자계 프로브를 이용하여 PCB상에서 표면 자계 분포를 측정하였으며, 시뮬레이션 결과와 비교하였다. 측정 결과와 시뮬레이션 계산 결과는 5차 하모닉 주파수까지 10 dB 이내로 일치함을 확인하였다.

• 대한방사선기술학회지:방사선기술과학
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• 제37권4호
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• pp.247-252
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• 2014

의료기관에서 사용되고 있는 전자파 방사선은 매우 다양한 에너지를 사용하고 있으며 연구자에 따라 고에너지의 전자파 방사선이 납치마와 상호작용을 한 후 차폐효과를 얻을 수 있다는 의견과 차폐가 효과가 없을 뿐만 아니라 오히려 피폭을 가중 시킨다는 상반된 의견이 제시되고 있다. 이에 본 연구에서는 몬테칼로 모사를 이용하여 전자파 방사선의 에너지에 따른 납치마의 차폐효과를 분석하고자 하였다. 몬테칼로 모사를 이용하여 전자파 방사선을 10 keV부터 500 keV까지 10 keV 단위로 1 MBq 방출시켜 납차폐체의 유무에 따른 선량차이를 차폐율로 표현한 결과 납차폐체(0.25 mmPb)를 사용하여 차폐를 실시하였을 때 고에너지 전자파 방사선에서 차폐율이 현저히 떨어져 차폐시 오히려 선량이 증가됨을 알 수 있었다.

• 한국전자파학회논문지
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• 제29권1호
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• pp.61-67
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• 2018

지하의 비균일성이 지하탐사레이다(GPR) 신호에서 금속관 탐지에 미치는 영향을 수치계산으로 조사하였다. 지하의 비균일성을 모델링하기 위해서 연속적인 랜덤 매질(CRM) 생성기법을 도입하였고, GPR 신호의 전자기 모의계산을 위해 유한차분시간영역(FDTD)법을 구현하였다. 랜덤 비균일 지하에 대한 상대 유전율 분포의 표준편차와 상관길이의 변화에 따라 매설된 금속관의 GPR 신호를 수치 모의계산으로 비교하였다. 지하의 비균일성이 증가함에 따라 지하 클러터의 영향으로 인하여 매설관에 의한 GPR 신호가 심하게 왜곡되었다.

• Journal of Magnetics
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• 제19권3호
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• pp.300-308
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• 2014

This paper develops a moving-magnet electromagnetic actuator for fast steering mirror (FSM). The actuator achieves a reasonable compromise between voice coil actuator and piezoelectric actuator. The stroke of the actuator is between the strokes of a piezoelectric actuator and a voice coil actuator, and its force output is a linear function of air gap and excitation current within our FSM travel range. Additionally, the actuator is more reliable than voice coil actuator as the electrical connection in the actuator is static. Analytically modeling the actuator is difficult and time-consuming. Alternatively, numerous finite element simulations are carried out for the actuator analysis and design. According to the design results, a real prototype of the actuator is fabricated. An experimental test system is then built. Using the test system, the force output of the fabricated actuator is evaluated. The test results validate the actuator analysis and design.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.43-46
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• 2003

This paper presents capacity characteristics of the indoor LOS(Line-Of-Sight) propagation channel for MIMO system at 5GHz. The distance between antenna elements, their moving path, and number of transmitting and receiving antennas can be determined by wanted eigen-vlaue, and channel capacity of the MIMO communication channel using only reliable simulation without measurements. The simulation uses 3D Ray tracing and patch scattering model to which electromagnetic material constants are applied. As distance between antenna elements increases, distribution of the eigen-value show a tendency to decrease, but channel capacity increases in LOS environment. However, despite of short distance between antenna elements, large value of channel capacity is obtained in positions which have high AS. When the position of receiver antennas are shifted, channel capacity hardly changed, and as number of antenna elements increases, channel capacity also increases regularly.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.565-571
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• 2013

This paper presents an effective method to improve efficiency of switched reluctance motor by optimizing energy conversion loop. A nonlinear analytical model which takes saturation account is developed to calculate inductance and flux-linkage. The flux-linkage curve is studied to calculate the co-energy increment to obtain the optimum exciting current. For a given cross-section, the exciting current at which co-energy increment is maximum was found to be constant while stack length varies. Then the energy conversion loop was optimized by varying the stack length and turns of windings. The constraints during optimization were that motor was excited by the maximum increment co-energy current and the energy in the loop was determined by rated power of motor. Dynamic finite element analysis was used to evaluate the efficiency of various models and the comparison of results shows promising effects of the proposed method. Experiment was also conducted to validate the simulation result.

• 대한전자공학회논문지TC
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• 제42권12호
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• pp.159-164
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• 2005

최근 정보량의 증가로 고속 디지털 회로를 요구하고 있다. 이에 따라 소형 고주파 회로에 전자기 특성이 중요하게 대두되었다. 그래서 불완전한 그라운드 상에 PCB 회로의 고속 디지털 전송라인에 대한 신호 집적도와 두 평행 선로 사이의 결합특성을 3차원 전자기 해석법인 시간영역 유한차분법을 이용하여 해석하였다. FDTD 시뮬레이션 결과는 상용 회로 소프트웨어 툴인 ADS 시뮬레이터와 비교하였고, 집중 소자 모델링, 주파수에 따른 슬롯에 의한 전자파의 방사 등을 해석하였다. 결과로써 마이크로스트립 선로 아래 슬롯이 있는 경우 신호의 전송에 큰 영향을 끼치는 것을 알 수 있다.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.719-728
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• 2013

Probabilistic assessment of voltage stability margin (VSM) with existence of correlated wind speeds is investigated. Nataf transformation is adopted to establish wind speed correlation (WSC) model. Based on the saddle-node bifurcation transversality condition equations and Monte Carlo simulation technique, probability distribution of VSM is determined. With correlation coefficients range low to high value, the effect of WSC on VSM is studied. In addition, two risk indexes are proposed and the possible threat caused by WSC is evaluated from the viewpoint of risk analysis. Experimental results show that the presence of correlated wind speeds is harmful to safe and stable operation of a power system as far as voltage stability is concerned. The achievement of this paper gives a detailed elaboration about the influence of WSC on voltage stability and provides a potentially effective analytical tool for modern power system with large-scale wind power sources integration.

• 한국군사과학기술학회지
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• 제19권3호
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• pp.294-301
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• 2016

In this paper, we designed the transparent circuit analog radar absorbing structure using printed metal grid mesh for enhanced optical transmittance. To obtain wideband electromagnetic absorption and enhanced optical transparency at X-band, we proposed the resistive FSS(Frequency Selective Surface) using printed metal mesh pattern on transparent glass with PEC(Perfect Electric Conductor) plane using ITO(Indium Thin Oxide) coating. We then fabricated the proposed structure to verify the simulation results obtained from commercial EM simulator. The comparisons between the simulation and measured results show good agreements. The results also show that the proposed radar absorbing structure can provide wideband reflection as well as better optical transparency. We can apply this proposed structure to the canopy of stealth aircraft and other stealth and security applications for visible transparency.

• Journal of electromagnetic engineering and science
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• 제12권4호
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• pp.287-289
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• 2012

This paper proposes an alternate time-switched space-frequency block coding transmission technique for orthogonal frequency division modulation systems. There are two antennas in the transmitter but it still has only a baseband and RF and a switch that alternates between the antennas at every symbol timing. Alternating transmit symbols result in zeros that make maximal ratio receive combining possible in the receiver. Simulation results show that it provides better performance than the traditional algorithm at the expense of one additional antenna.