• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2028-2030
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• 1999

In this paper, partial discharge(PD) was generated under the two types of needle -plane electrodes in the air. Using a monopole antenna to detect the radiated electromagnetic waves by stream of charge between the electrodes. the progress of partial discharge was studied. To analyze the progress of PD, statistical re-search was introduced. It was executed by personal computer and it can be possible to visualize the progress of PD. The t-test was used for lower voltage applied. The population of background noise spectrum and applied voltage spectrum showed the difference. The new method was introduced to analyze the spectrum. According tho the magnitude of applied voltage, the different statistical methods were used. The results obtained from this work will provide the useful information on partial discharge in time to come.

• ETRI Journal
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• 제38권6호
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• pp.1052-1063
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• 2016

We propose a millimeter wave (MMW)-based mobile hotspot network (MHN) system for application in high-speed railways that is capable of supporting a peak backhaul link throughput of 1 Gbps per train at 400 km/h. The MHN system can be implemented in subways and high-speed trains to support passengers with smart devices and provide access to the Internet. The proposed system can overcome the inherent high path loss in MMW through system designs and high antenna gains. We present a simulation of the system performance that shows that a fixed beamforming strategy can provide high signal-to-interference-plus-noise-ratio similar to those of an adaptive beamforming strategy, with the exception of 15% of the train path in which the network can use link adaptation with low-order modulation formats or trigger a handover to maintain the connection. We also demonstrate the feasibility of the MHN system using a test bed deployed in Seoul subway line 8. The backhaul link throughput varies instantaneously between 200 Mbps and 500 Mbps depending on the SNR variations while the train is running. During the field trial, the smartphones used could make connections through offloading.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.2043-2046
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• 2002

This paper studies on Sun interference effects or Sun outage effects on C-band satellite reception signal for THAICOM2. The THAICOM2 satellite is at 78.5 degree East 〔co-located with THAICOM3〕. The down link station was located in Khon-kaen, longitude 102.83 degree East and latitude 16.43 degree North. The antenna diameter is 4.6 meters for C-band downlink station. Total 9 times of sun interference events were occurred during summer and fall of 2001 and these about 53 minutes altogether. The Maximum CM degradation of the THAICOM2 system was around 11 dB. The Sun interference events of 53 minutes of one year are 0.0122 percents of the C-band contact time when 21 hours of contact time is used f3r broadcasting a day.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 추계종합학술대회
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• pp.167-171
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• 2002

CDMA 시스템의 채널을 여러 사용자가 공유하면 수신기는 MAI 문제에 직면하고 또한 다중로 시나리오는 ISI를 유발한다. 두 요소는 원치 않는 성분이지만 완전히 예측할 수 없는 부가 잡음과는 다르게 이러한 요소의 시공간 구조는 이들을 추정하고 제거하는데 도움이 된다. 본 논문은 다중로를 가진 페이딩 채널에 대한 연구이며 채널 추정 부분과 수신 부분을 분리하였다. 추정 부분은 DOA와 TOA 같은 다중로 파라미터를 추정하고 수신 부분은 역상관 빔포머, 시공간 정합필터, Winer-Hopf 빔포머에 대하여 평가한다. 여러 가지 추정 기술과 빔포머의 평가를 이론치와 비교하여 시뮬레이션 하였다.

• 한국통신학회논문지
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• 제30권12C호
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• pp.1222-1230
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• 2005

본 논문에서는 Space-Time code를 사용하는 다중 안테나 시스템에서 Hybrid automatic retransmission request (HARQ)의 처리능력(throughput)을 향상시키는 기법을 제안한다. 우선 낮은 복잡도를 가지는 Hard decision decoding (HDD) 방법에서 신뢰도 정보를 이용하여 복호 성능을 높일 수 있는 알고리즘을 제안한다. 이렇게 제안된 알고리즘을 HARQ 프로토콜을 사용하는 시스템에 사용하여 낮은 복잡도를 유지하면서 전체 처리능력을 향상시킬 수 있도록 한다. 제안된 기법의 성능을 확인하기 위하여 처리능력을 수학적으로 분석하였으며, 모의실험을 통해 AWGN 채널 및 페이딩이 있는 다중입력 다중출력 채널뿐만 아니라 Impulse 잡음이 있는 환경에서도 성능이 향상됨을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1957-1959
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• 2000

The PD measurement method is very useful to detect insulation degradation. Recently, the HFPD(High Frequency Partial Discharge) measurement testing is widely used in partial discharge measurement of HV machines because HFPD measurement testing receives less influence of external noise and has a merit of good sensitivity. Therefore it is very useful method compare to previous conventional PD testing method and effective diagnosis method in power transformer that requires in-service diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In this study, simulated transformer is manufactured and HFPD occurred from simulated transformer is measured with broad band antenna and active-line RF measurement system in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages. Also the PD pattern which was measured with EMC analyzer and RF measurement system is compared.

• 대한기계학회논문집A
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• 제26권4호
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• pp.602-608
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• 2002

The flexible structure like solar array and antenna in spacecraft shows very sensitive responses to the inner or outer disturbance and noise. And the spacecraft becomes more complex and larger as it has various mission and role. But since the spacecraft need to have the limited mass, the thin and light material should be selected and this necessity induces the decrease d natural frequency and structural stiffness. It reduces the ability of adapting to the disturbance and induces the structural unstability. Certainly, the disturbance does not only make the structural unstability, but also give the bad effect to the precise attitude control. So it is necessary to control the vibration in the space. In this paper, the flexible structure control modeling with piezo sensor and piezo actuator is developed. The model uncertainty of damping ratio is overcome by robust control. The system equation is induced by the finite element method.

• 조명전기설비학회논문지
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• 제15권1호
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• pp.104-111
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• 2001

본 연구에서는 대기중 두가지 형태의 전극부에서 부분방전(partial discharge : PD)시 방사되는 VHF(30∼230 [MHz])대역의 방사전자파를 측정하고, 그 스펙트럼의 특이한 패턴을 나타냈다. 또한 PD에 의해 방사되는 방사전자파에 대한 거리 및 편파특성에 관하여 연구하였다. 에폭시절연체를 삽입한 경우, 방사전자파의 잡음레벨은 90 [MHz] 대역 이하에서 대기중에 비하여 0.6∼6.2 [db] 높게 나타났다. 방사전자파의 스펙트럼 분포는 안테나 엘리먼트 배치에 따라 전주파수 영역에서 차이를 나타내고 있다.

• 조명전기설비학회논문지
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• 제22권12호
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• pp.164-175
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• 2008

안개 및 대기의 교란이 광무선 통신에 주는 영향을 해석하기 위해 가시광선영역의 LD(laser diode) 및 적외선 영역의 LD 사용하고, 카세그레인 광학계를 이용하여 광을 송수신하게 하였으며, 광 소신소자로는 APD(avalanch photo diode)를 사용함을 가정하여 대기 중의 안개의 정도에 따른 가시도 및 교란의 세기를 나타내는 굴절률 구조상수에 따른 광 수신 전력, 잡음 전력을 고려한 SNR(signal to noise ratio)을 계산해 보고 각각의 통신 상태에서 BER(bit error rate)이 $10^{-9}$이 가능한 통신 거리를 알아보았다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 유기절연재료 방전 플라즈마
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• pp.50-54
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• 2000

Recently, the HFPD measurement testing is widely used in partial discharge measurement of HV machines because HFPD measurement testing receives less influence of external noise and has a merit of good sensitivity. Also HFPD testing is able to offer the judgement standard of degradation level of HV machine and can detect discharge signals in live-line. Therefore it is very useful method compare to previous conventional PD testing method and effective diagnosis method in power transformer that requires live-line diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In recent, the study of partial discharge is carrying out discover of initial defect of power equipment through condition diagnosis and system development of degradation diagnosis using HFPD(High Frequency Partial Discharge) detection. In this study, simulated transformer is manufactured and HFPD occurred from transformer is measured with broad band antenna in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages.