• 한국전자파학회논문지
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• 제18권5호
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• pp.471-477
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• 2007

본 논문은 전자파 장해 및 복사 내성 측정의 대용 시험 시설로서 활용될 수 있는, 다중 유전체로 구성된 평탄형 QRD(Quadratic Residue Diffuser)를 사용한 전자파 잔향실에 대한 연구이다. 잔향실은 $2.5{\sim}3$ GHz 대역에서 사용 가능하도록 설계되었으며, 기존 QRD의 특성을, 다양한 유전체를 이용하여 낮은 평탄형 구조물로 구현하였고, 이를 적용한 전자파 잔향실 내부에서의 전자기장 특성 변화 및 시험 공간 확장에 관해서 비교 분석하였다. 잔향실 내부의 전자기장 분포 해석을 위해서 FDTD(Finite-Difference Time-Domain) 수치 해석 방식을 이용하였다. 잔향실 내에 새로 제안된 확산기를 사용하면, 기존 확산기에 비해 물리적인 크기가 줄어들 뿐만 아니라 전자기장 균일도, 편파 특성 및 공차 등의 성능이 비슷하거나 우수해짐을 확인하였다. 따라서 다중 유전체로 구성된 평탄형 확산기를 사용한 잔향실이 기존의 QRD를 사용한 잔향실에 비해 전자기적 성능 및 공간 활용면에서 우수한 시험시설임을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 영호남 합동 학술대회 및 춘계학술대회 논문집 센서 박막 기술교육
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• pp.74-76
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• 2006

An external electrode fluorescent lamp (EEFL) has an advantage of a long lifetime in the ear1y stages of the study on plasma discharge, interest in the lamp continues. Researches on the operation of external electrode fluorescent lamps have focused mainly on its use of a type of high frequency (MHz). By performing high brightness using a square wave operation method with the low frequency below 100kHz, which is applied to a narrowed tube type lamp that has several mm of lamp diameter, EEFL presented the possibility of using it as a light source for back-lights. However, because EEFL generates plasma using wall charges, which considers the impedance characteristics of glass based on the structural principle in discharge, it can be significant1y affected by frequency. Thus, this study verified the change in the characteristics of electromagnetic fields according to the change in frequency through a Maxwell's electromagnetic field simulation and examined the relationship between the change in the EEFL frequency and brightness by measuring the optical characteristics. In addition, the characteristics of the transformation of energy orbits were verified by investigating the characteristics of the wavelength according to the change in frequency through the OES.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 광주전남지부
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• pp.75-78
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• 2006

An external electrode fluorescent lamps (EEFLs) have the advantage of a long lifetime in the early stages of the study on plasma discharge, interest in the lamp continues. Studies on the operation of external electrode fluorescent lamps have focused mainlyon its use of a type of high frequency (MHz). By performing high brightness using a square wave operation method with the low frequency below 100kHz, which is applied to a narrowed tube type lamp that has several mm of lamp diameter, an EEFL presented the possibility of using it as a light source for backlights. However, because an EEFL generates plasma using wall charges, which considers the impedance characteristics of glass based on the structural principle in discharge, it can be significantly affected by frequency. Thus, this study verifies the change in the characteristics of electromagnetic fields according to the change in frequency through a Maxwell's electromagnetic field simulation and examines the relationship between the change in the EEFL frequency and brightness by measuring the optical. characteristics. In addition, the characteristics of the transformation of energy orbits were verified by investigating the characteristics of the wavelength according to the change in frequency through the OES.

• 한국전자파학회논문지
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• 제14권1호
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• pp.54-61
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• 2003

본 논문은 중 전압 전력선(22.9 kV)에서 방사되는 전자파 특성결과를 보여주고 있다. 측정은 주파수범위 9 kHz∼30 MHz의 통신 신호를 중 전압 전력선로에 인가하였을 때 측정을 하였다. 측정결과 단일 반송신호보다 다중 반송신호에서 방사되는 전자파의 특성이 우수하며 다중반송신호의 세기가 20 dBm일 때 전력선 통신 신호는 1.8 km까지 전송 가능함을 알 수가 있었다. 전기장의 세기는 10 m 법으로 측정하였을 때 30 MHz에서 40 dBuV/m이하의 값을 볼 수가 있었다.

• 한국전자파학회논문지
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• 제19권3호
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• pp.304-310
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• 2008

이동 통신용 안테나로 PEC(Perfect Electric Conductor) 접지면을 갖는 U-slotted 패치 안테나가 널리 이용되고 있으나, 이동 통신 능력을 확대하기 위하여 대역폭의 개선이 요구되어 왔다. 본 논문에서는 대역폭을 확대하기 위하여 EBG(Electromagnetic Band-Gap) 접지면을 갖는 U-slotted 패치 안테나를 제안하고, 그 복사 특성을 고찰하였다. 본 논문에서 제안한 EBG 접지면을 갖는 U-slotted 패치 안테나의 대역폭이 개선됨을 보이기 위하여 EBG와 PEC 접지면을 갖는 두 가지 형태의 U-slotted 패치 안테나를 설계 제작하고 복사 특성을 측정하였다. 측정결과, EBG 접지면을 갖는 U-slotted 패치 안테나가 PEC 접지면을 갖는 안테나보다 대역폭이 넓은 것으로 확인되었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권9호
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• pp.648-655
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• 1999

In this study, a relationship between DC discharge and the radiated electromagnetic waves is investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The characteristics of frequency spectrum ofthe radiated electromagnetic waves was measured at the atmospheric pressure in Liquid Nitrogen $(LN_2)$ during partial discharges in nonuniform and uniform electric field depend on positive DC power. From this experiment results, it was confirmed that when partial discharge was produced in Liquid Nitrogen and Air, the signal of partial discharge was detected by this experiment and the analysis method. It is considered thatthese results obtained from this investigation may be used as fundamental data for diagnosis and prediction of insulation on the equipments ultra-high voltage, superconducting and cryogenic applications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1975-1977
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• 2000

In this study, a relationship between AC discharge progress and the radiated electromagnetic waves were investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The characteristics of frequency spectrum of the radiated electromagnetic waves was measured at the atmospheric pressure in liquid nitrogen($LN_2$) during partial discharges progress in nonuniform electric field depend on AC power supply. From this results, it was confirmed that when partial discharge was produced in liquid nitrogen, the signal of partial discharge was detected by frequency spectrum of the radiated electromagnetic waves. It is considered that these results obtained from this investigation may be used as fundamental data for diagnosis and prediction of insulation on superconducting and cryogenic power equipments.

• Carbon letters
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• 제15권4호
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• pp.268-276
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• 2014

Recently, methods that usea carbon-based filler, a conductive nanomaterial, have been investigated to develop composite fillers containing dielectric materials. In this study, we added geometric changes to a carbon fiber, a typical carbon-based filler material, by differentiating the orientation angle and the number of plies of the fiber. We also studied the electrical and electromagnetic shield characteristics. Based on the orientation angle of $0^{\circ}$, the orientation angle of the carbon fiber was changed between 0, 15, 30, 45, and $90^{\circ}$, and 2, 4, and 6 plies were stacked for each orientation angle. The maximum effect was found when the orientation angle was $90^{\circ}$, which was perpendicular to the electromagnetic wave flow, as compared to $0^{\circ}$, in which case the electrical resistance was small. Therefore, it is verified that the orientation angle has more of an effect on the electromagnetic interference shield performance than the number of plies.

• Journal of Power Electronics
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• 제17권6호
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• pp.1683-1693
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• 2017

This paper analyses the harmonic pollution to power grids caused by thyristor-controlled devices. It also formulates a mathematic derivation for the voltage spikes in thyristor-controlled branches to explain the harmonic and EMI derived from the reverse-recovery characteristics of the thyristor. With an equivalent nonlinear time-varying voltage source, a detailed simulation model is established, and the periodic dynamic switching characteristic of the thyristor can be explicitly implied. The simulation results are consistent with the probed results from on-site measurements. An improved trigger system with gate-shorted circuit structure is proposed to reduce the voltage spikes that cause EMI. The experimental results indicate that a prototype with the improved trigger system can effectively suppress the voltage spikes.

• 한국군사과학기술학회지
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• 제27권1호
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• pp.15-23
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• 2024

In order to avoid the high observability due to the cavity resonance or electromagnetic wave leakages from the bridge of a battleship or the cockpit of an aircraft, this paper presents a transparent conductive oxide coated structure to prevent the incoming/outgoing electromagnetic waves. Currently, most of the RCS reduction technologies were focused on radar absorbing material such as paints based on conductive or magnetic materials in the fuselage, and there is not much research on countermeasures for achieving the low observability of materials that required optical transparency in actual weapon systems. In this study, the transmission/reflection and absorption performance of the ITO coated structure according to the change of the surface resistance of the transparent conductor were analyzed. Finally, the relationship between the electromagnetic and optical characteristics was established through fabrication and measurement.