• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.101-103
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• 2013

최근 HD (High Definition) 또는 3D (Three Dimension) 이상의 고품질 방송 콘텐츠 수요가 증가하면서 디지털 방송 시스템은 실시간으로 실감형 서비스를 제공하기 위하여 발전 하였다. 특히, 세계 방송 비영리 협회 FoBTV (Future of Broadcast Television) 는 더 나아가 초 고해상도 UHD (Ultra High Definition) 급 이상의 영상을 제공하기 위해 지상파 방송과 유선 케이블 방송 시스템을 이용하여 고품질, 다시점 방송 서비스 뿐 아니라 낮은 전계 강도 환경에서 수신율을 높일 수 있는 기술방안을 논의하고 있다. 본 논문은 이와 같은 세계 방송 발전 흐름에 따라 지상파 및 케이블 방송 송수신 시스템을 구현하고 수신되는 영상의 품질을 평가하였다. 또한, 구현된 통합 시스템은 지상파로 수신되는 파일럿 신호의 크기를 분석하여 케이블로 재전송 되며 이를 통해 수신 성능의 품질을 향상시킨다.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.302-305
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• 2000

최근에 ITU-R에서 30～3,000MHz 주파수 범위에서 사용할 수 있는 포괄적인 전계 강도 커브를 제시하고 있다. ITU-R Question 중의 하나인 의제 210/3에서 요구하는 내용은 '30MHz～3GHz 대역의 육상이동과 지상방송 업무를 위한 전파전파 예측절차'이다. 이러한 의제를 WP SG3에서 연구하여 부속서 3K/TEMP/4에 정리하였다. 본 논문에서는 위 부속서 3K/TEMP/4에 나와있는 전송손실 예측 그래프의 적용범위와 적용환경을 알아보기 위해 일반적인 실험적 경로손실 예측식인 Okumura-Hata 모델 그리고 Cost231-Hata 모델과 비교 분석하였다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.01a
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• pp.233-236
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• 2012

본 연구에서는 변성기용으로 사용되는 에폭시 복합체에 대해 절연 파괴 실험을 하고 그 데이터를 와이블 분포 확률을 이용해서 시뮬레이션을 하였다. 에스테르기의 기여에 의한 가교밀도 때문에 저온에서 경화제가 증가할수록 파괴강도가 증가하고 충진제를 첨가한 시료들의 파괴강도는 비충진 시료들의 경우 보다 더 낮았는데 이는 충진제 첨가가 계면을 형성하고 전하가 축적되어 분자의 이동도가 증가되고, 전계가 집중되어 전자 가속화 및 전자 사태의 성장이 초기에 도달되기 때문으로 사료된다. 또한 와이블 분포의 분석으로부터 허용 절연파괴 확률이 0.1[%]로 주어질 때, 인가 전계값은 21.5[kV/mm] 이하가 되어야 함을 확인하였다.

• 전기의세계
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• v.27 no.3
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• pp.3-6
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• 1978

SF$_{6}$gas는 고정압 게통의 모든 분야에 광범위하게 사용되여 차단기의 소호재료로써 또는 초초고압용의 cable 및 변압기등의 절연재료로써 많이 사용되어지고 있다. 이러한 모든 분야에서 보여주는 SF$_{6}$gas의 우수한 절연특성은 이 Gas의 사용범위를 더욱 확대시켜 줄 것이라고 생각된다. 그러나 이러한 높은 절연강도도 고기압하에서는 기대되어지는 절연강도 보다 훨씬 낮아지는 경향이 있으며 이러한 경향은 사용압력이 높아질수록 현저하다. 그러나 고전압용 전기기기의 절연재료로써 고기압의 SF$_{6}$gas가 점차적으로 많이 사용되고 있기 때문에 이 고기압 SF$_{6}$에 관한 연구 결과중 우선 여기서는 평등전계에서 전극표면상태 및 면적등에 의한 영향과 절연파괴 직전의 전류펄스에 대한 것을 저기압 SF$_{6}$gas에 관한 결과와 함께 기술하고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.6
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• pp.824-834
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• 1993

In cellular mobile communication systems, if the size of a cell is decreasing for economic utilization of frequency resources, frequent handovers may be requested because the time a mobile stays in a cell is decreasing. In general the measured parameters to decide handover including RSSI, BER, and the distance between mobile station and base station, are usually incorrect and handover decision using single parameter insufficient. Therefore, the better handover algorithm should take over the problems of this uncertain measurements, and make the decision more robust and flexible by the consideration of all those decision parameters at the same time. We propose a novel handover algorithm based the multicriteria decision making, in which those parameters are participated in the decision process using aggregation function in fuzzy set theory. As a simulation results, the overall decision making is more reliable and flexible than the conventional method using only one parameter, RSSI in terms of call force ratio, and handover request ratio.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.2
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• pp.31-40
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• 1999

Characteristics of monopole antenna and planar conductor structure mounted on handheld telephone are anlayzed by using FDTD method. Feeding of monopole antenna is implemented with lumped elements and plastic case is coated on the surface of conductor box. Otherwise, resonant frequency of handheld telephone mounting monopole antenna with no plastic case is 877MHz, when plastic case (${\varepsilon}_r=2$) is coated, the resonant frequency is down to 82MHz and the bandwidth is broadened about 1.5 times. Planar structure of handheld telephone mounted on the body makes to change far-field gain radiation patterns. In this case, radiation patterns are somewhat asymmetrical. Handheld telephone using PIFA(Planar Inverted F Antenna), instead of monopole antenna, is resonated at frequency 1.52GHz that is available onPCS. In the radiation pattern of this structure, azimuth that electric field intensity is presented below 20dB is 14$^{\circ}$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.10
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• pp.121-127
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• 2009

This paper reviews a basic data of the surface discharge characteristics for tefton resin in not only pure $N_2$, $N_2:O_2$(80[%]:20[%], I-Air) and $N_2:O_2$(60[%]:40[%]) mixture gas as environment-friendly insulation Gas also $SF_6$. Used electrodes are Knife to Knife. With the changing distance of electrodes and pressure, we can find it, surface discharge voltages and surface dielectric strengths, respectively. Surface discharge Voltages of I-Air are more higher than the other $N_2/O_2$ mixture gases. Moreover, we can obtain that the surface dielectric strengths of $SF_6$ are two times about I-Air, approximately.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.4
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• pp.18-24
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• 2010

This paper presents the improvement of the field uniformity in a reverberation chamber which can be substitute an anechoic chamber for the electromagnetic interference (EMI) and immunity test. Nowadays, there are many EMI issues due to the increasing use of wireless local area network (LAN), digital multimedia broadcasting (DMB), and mobile internet. With this reason, this paper studied the field characteristics in a reverberation chamber for 2.3 GHz band. In this paper, the finite difference time domain (FDTD) method is used to analyze the field characteristics in a reverberation chamber. To improve the field uniformity in the reverberation chamber, this paper adopted a 2D cubical residue diffuser (CRD) with varying the disposition and number of CRD. For each case, the tolerance and standard deviation of the electric field strength are evaluated. In comparison with the reverberation chamber without any CRD, the reverberation chamber with two CRDs showed improved results; 1.98 dB improvement in standard deviation and 3.6 dB improvement in tolerance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.580-586
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• 2008

The prediction of a system coverage is required to install or operate a base station of the differential global positioning system(DGPS). However, the predicted results differ from the measured results when those are analyzed using ITU-R effective ground conductivity values. Thus, in this paper, the coverages of DGPS reference stations are analyzed using the modified effective ground conductivity values. The modified effective ground conductivity is based on the effective ground conductivity of ITU-R and modified to minimize the error between the measured electric fields and the predicted electric fields by using a statistical method. Then, the DGPS system coverages are analyzed by using the modified effective ground conductivity values, and the system stability is verified with a various analysis.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.636-650
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• 2008

DTV has a great advantage as compared to Analog TV in picture quality under low reception field strength. Various high quality tuners have been developed to result in much smaller Noise Figure of the receivers and many trials for receiving DTV signal through indoor antenna. In this paper, results of intensive field tests on the indoor reception of DTV are presented. Tests were carried out around Seoul-Gyeonggi Metropolitan area. Commercial directional and omni-directional antennas and 5th generation receiver were used for reception availability tests. The effects of heights, locations, and types of the house as well as the distance to the transmitter on the reception performances are analyzed. Our test results will be applied to improve the indoor reception environment of DTV.