• 폴리머
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• 제24권6호
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• pp.860-868
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• 2000

본 연구에서는 섬유등급, 배향각 및 적층방법을 달리하여 제조한 탄소섬유강화 복합재료의 제조변수에 따른 전자파 차폐 특성에 관하여 고찰하였다. 그 결과, 탄소섬유강화 복합재료의 전자파 차폐효과는 섬유의 배향각도에 크게 좌우되었다. 특히 0$^{\circ}$의 배향각에서는 섬유의 등급에 따른 영향을 나타내었으며, 동일한 탄소섬유라 할지라도 배열방향에 따른 전기적 성질의 변화, 즉 전기적 이방성이 클수록 차폐효과는 커졌다. 각각의 적층방법에 따라 제조된 모든 시편은 83~98%의 차폐효과를 나타내었으나, 대칭구조와 비대칭구조에서는 적층각도가 커짐에 따라 차폐효과가 소폭 감소하였다. 그러나 반복구조에서는 위의 두 가지 구조와는 다른 경향을 나타내었으며, 특히 90$^{\circ}$ 반복구조의 경우 측정 주파수 전 영역에 걸쳐 90% 이상의 차폐력을 나타내었다.

• 한국항공우주학회지
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• 제48권1호
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• pp.63-72
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• 2020

본 연구에서는 위성용 전장품 보드의 성능 요구조건과 설계 복잡도가 높아지면서 증가되는 노이즈 문제를 최소화하기 위해 전원 건전성(Power Integrity) 및 신호 건전성(Signal Integrity)의 설계 분석이 수행되었고 이를 통해 적용된 설계 개선 내용을 기술하였다. 전원 건전성은 정전류 전압강하(DC IR drop) 해석을 통해 정적 전원의 특성을 분석하였고, 각 전원의 임피던스 해석을 통해 동적 전원의 특성을 분석하여 각 분석 결과를 이용한 설계 개선 방안들이 적용되었다. 신호 건전성 측면에서는 주요 데이터버스 신호에 대한 시간영역 파형 분석과 PCB(Printed Circuit Board) 설계 수정을 통해 노이즈가 개선된 결과를 확인하였다. 또한 설계된 PCB 보드의 전원 층에 대한 공진모드를 분석하여 발생된 공진 영역들에 완화 조치를 적용하였고 조치결과를 시뮬레이션을 통해 확인하였다. 최종적으로 분석을 통해 설계 개선이 적용된 유닛에 대해 수정 전과 후의 EMC(Electro Magnetic Compatibility) RE(Radiated Emission) 노이즈 측정결과를 비교함으로써 방사성 노이즈가 감소되었음을 확인하였다.

• 한국전자파학회논문지
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• 제17권5호
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• pp.423-429
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• 2006

본 논문은 실용적인 면을 고려한 휴대전화 단말기용 전파 흡수체 개발을 위해 연구하였다. 이에 Sendust 배합율, $Al(OH)_3$ 코팅 함유량, 시편의 두께, 지지재의 변화가 전파 흡수체의 전파 흡수능에 치는 영향을 연구하였다. 중심 주파수는 전파 흡수체의 두께가 1 mm, 2 mm, 3 mm로 증가할수록 2.2 GHz, 1.29 GHz, 842 MHz의 저주파대로 이동하였고, Sendust의 배합율이 80 wt%에서 85 wt%로 증가되면서 2.2 GHz에서 1.91 GHz로, 1.29 GHz에서 801 MHz로, 842 MHz에서 801 MHz로 각각 저주파대로 조절할 수 있었다. 전파 흡수 대역은 Sendust에 $Al(OH)_3$를 코팅했을 때가 코팅하지 않았을 때보다 흡수 대역이 넓어졌다. 이때 전파 흡수체는 지지재는 CPE로 하였으며, 제작 온도는 $70^{\circ}C$로 일정하게 하였다. 제작된 전파 흡수체는 두께가 0.85 mm일 때 1.8 GHz에서 5.76 dB의 우수한 전파 흡수능을 보였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.751-755
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• 2003

In this paper, We proposed compact multi-layer LTCC (Low Temperature Cofired Ceramic) bandpass filter for Bluetooth module. A ${\lambda}/4$ coupled stripline resonators are designed, which composed of coupled strip-line section and loading capacitance. This resonator with a loading capacitor has slow-wave characteristics. Due to the slow-wave effect of the proposed resonator, it is possible to design and fabricate a compact bandpass filter with a wide upper stop band. Attenuation poles in the lower stop band are achieved using controlling of electro-magnetic coupling between resonators. Using multi-layer LTCC technology, we designed and fabricated band pass filter with a finite attenuation pole and wide upper stopband. The overall size of the filter is $1.2{\times}2.0{\times}1.0mm^3$.

• 전기학회논문지
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• 제61권8호
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• pp.1210-1215
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• 2012

Traction motors for driving and power conversion devices using semiconductor switch are equipped with a transportation systems such as an electrical railway system. Power conversion devices have the possibility of malfunction by external electromagnetic waves. As a result, these could affect the safe operation of the railway. Moreover, the electromagnetic waves above safe limits will be harmful to the passengers inside the railway vehicles or anyone working around the rail-track. For this reason, the importance and need about the reliability check and complement of electromagnetic waves generated from the IPT(Inductive Power Transfer) system have been suggested for the safe application of the IPT system to the railway system. In this study, prediction for the electromagnetic wave properties was conducted through FEM(Finite Element Method) analysis of 5kW-class IPT system design model. Next, the 5kW IPT system prototype was made and then the small-scaled railway vehicle was made to mount the IPT system and the energy management system. Finally, the electromagnetic waves generated from the real small-scaled IPT system were measured and analyzed, and then the reliability check of predictions by FEM analysis were carried out.

• Biomolecules & Therapeutics
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• 제22권6호
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• pp.570-576
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• 2014

Studies have demonstrated that electromagnetic waves, as the one of the most important physical factors, may alter cognitive and non-cognitive behaviors, depending on the frequency and energy. Moreover, non-ionizing radiation of low energy waves e.g. very low frequency waves could alter this phenomenon via alterations in neurotransmitters and neurohormones. In this study, short, medium, and long-term exposure to the extremely low frequency electromagnetic field (ELF-EMF) (1 and 5 Hz radiation) on behavioral, hormonal, and metabolic changes in male Wistar rats (250 g) were studied. In addition, changes in plasma concentrations for two main stress hormones, noradrenaline and adrenocorticotropic hormone (ACTH) were evaluated. ELF-EMF exposure did not alter body weight, and food and water intake. Plasma glucose level was increased and decreased in the groups which exposed to the 5 and 1Hz wave, respectively. Plasma ACTH concentration increased in both using frequencies, whereas noradrenaline concentration showed overall reduction. At last, numbers of rearing, sniffing, locomotor activity was increased in group receiving 5 Hz wave over the time. In conclusions, these data showed that the effects of 1 and 5 Hz on the hormonal, metabolic and stress-like behaviors may be different. Moreover, the influence of waves on stress system is depending on time of exposure.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1814-1816
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• 2004

현장에서 많이 사용되고 있는 GIS에 결함이 발생하면 치명적인 사고로 진전될 수가 있다. 본 논문은 모의 GIS내 도전성 금속이물질 존재 시 발생되는 부분방전 신호를 절연진단 방법중 하나인 UHF법을 이용하여 부분방전 시 방사되는 방사전자파의 스펙트럼을 분석해서 방사전자파의 거리에 따른 감쇄율을 측정하였다. 이러한 연구는 현장 GIS 및 $SF_6$ 가스절연 전력설비에서 금속이물질에 의해 발생되는 방사전자파 측정에 중요한 역할을 할 것으로 사료된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1986년도 하계학술대회논문집
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• pp.591-594
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• 1986

An asymptotic solution of electro-magnetic waves diffracted by a dielectric wedge of the angle larger than $180^{\circ}$ is obtained in case of the incidence of a E-polarized plane wave. Based on the dual integral equation in the spectral domain, physical optics approximation is supplemented by correction currents distributed along the interfaces. Those currents are expanded in a series of Bessel functions, known as Neumann's expansion of which fractional order is chosen to satisfy the static edge condition as the limiting value of dynamic case. Numerical results of edge diffraction patterns and field patterns are presented for some typical cases.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.477-480
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• 2005

In this paper, the concept of sustainability was applied to mechanical design and manufacturing of mobile-phone case. A new evaluation method to find products' good and weak point for sustainability was developed. Two mobile phones were evaluated using the evaluation tool. As a result, electro-magnetic (EM) wave was considered as a harmful factor of the products, and improved front panel was made using nano particles that absorb EM waves. The EM shielding tests revealed that silver nano powders absorbed EM while MWCNT had no effect.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권2호
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• pp.63-66
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• 2005

This paper describes analysis and pattern recognition techniques for Partial Discharge(PD) signals in Gas Insulated Switchgears (GIS). Detection of PD signals is one of the most important factors in the predictive maintenance of GIS. One of the methods of detection is electro magnetic wave detection within the Ultra High Frequency (UHF) band (300MHz $\~$ 3GHz). In this paper, PD activity simulation is generated using three types of artificial defects, which were detected by a UHF PD sensor installed in the GIS. The detected PD signals were performed on three-dimensional phi-q-n analysis. Finally, parameters were calculated and an Artificial Neural Network (ANN) was applied for PD pattern recognition. As a result, it was possible to discriminate and classify the defects.