• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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• pp.158-159
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• 2003

In four-wave-mixing wavelength converter, we investigated the performance through simulation by using VPI tool, changing the input signal power and CW power at 2.SGb／s. Controlling optimal CW power to each input signal power, we extended the input signal power range to 20dB, which guarantees the minimum power penalty.

• 전기학회논문지
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• 제57권2호
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• pp.268-275
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• 2008

In this paper, we introduce a new method for detecting and estimating faults on a power line using the time-frequency domain reflectometry system. The system rests upon time-frequency signal analysis and uses a chirp signal which is multiplied by Gaussian envelope. The chirp signal is used as a reference signal, and we can get the reflected signal from a fault on a wire. To detect and estimate faults, we analyze the reflected signal by Wigner time-frequency distribution function and normalized time-frequency cross correlation function. In this paper we design an optimal reference signal for power line and implement a system for estimating fault distance on a power line with the TFDR implemented by PXI equipments. This approach is verified by some experiments with HIV 2.25mm power lines.

• Journal of Power Electronics
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• 제16권2호
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• pp.805-814
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• 2016

Electric-field coupled power transfer (ECPT) systems have been proposed as an alternative wireless power transfer (WPT) technology in recent years. With the use of capacitive plates as a coupling structure, ECPT systems have many advantages such as design flexibility, reduced volume of the coupling structure and metal penetration ability. In addition, wireless communications are effective solutions to improve the safety and controllability of ECPT systems. This paper proposes a power and signal shared channel for electric-field coupled power transfer systems. The shared channel includes two similar electrical circuits with a band pass filter and a signal detection resistor in each. This is designed based on the traditional current-fed push-pull topology. An analysis of the mutual interference between the power and signal transmission, the channel power and signal attenuations, and the dynamic characteristic of the signal channel are conducted to determine the values for the electrical components of the proposed shared channel. Experimental results show that the designed channel can transfer over 100W of output power and data with a data rate from 300bps to 120 kbps.

• 융합신호처리학회논문지
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• 제7권4호
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• pp.184-188
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• 2006

본 논문은 협대역의 위성통신 수신신호 전력을 측정하여 이동형 위성통신 안테나를 추적제어하기 위한 DSP 기반의 협대역 위성통신 신호전력 검출기를 제안한다. 기존의 아날로그 검출방식에 의한 협대역 위성통신 신호전력 검출기는 위성 전파경로 상에서 발생되는 반송파의 중심주파수 천이로 인해 고정된 아날로그 필터대역을 통과하여 검출되는 신호 전력의 오차가 심하고 전송 신호의 대역폭 가변에 따른 아날로그 필터의 대역폭을 변경하기가 용이하지 않다. 따라서 이러한 반송파 주파수 천이에 영향 받지 않고 가변 하는 신호 대역폭에 대응하는 필터를 실시간으로 프로그래머블하게 지원하기 위하여 DSP 기반의 협대역 디지털 위성통신 신호전력 검출기를 제안하였다. 제안된 협대역 위성통신 신호전력 검출 알고리즘은 FFT를 이용하여 주파수 천이된 협대역 위성통신 신호의 주파수를 탐색하고 프로그래머블한 디지털 필터를 선택하여 필터링한 다음, 일정구간 주기로 신호전력을 계산하여 12비트 해상도로 출력하는 기능을 가진다. TMS320C5402 DSP 칩을 기반으로 설계 제작된 신호전력 검출기의 실제 시험을 통하여 제시된 요구기능과 규격을 만족하면서 동작함을 검증하였고 실용성을 확인하였다.

• 한국광학회지
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• 제2권2호
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• pp.67-73
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• 1991

단일 종모드로 동작하며, 10mW의 출력을 가지는 AlGaAs 반도체 레이저를 이용하여 Fabry-Perot 공진기형 레이저 증폭기 시스템을 구성하고 비포화 신호이득(unsaturated signal gain), 신호이득 대역폭(signal gain bandwidth), 포화출력(saturation power)을 측정하였다. 증폭기 레이저의 펌핑전류에 따른 비포화 신호 이득은 발진 문턱 전류 근처에서 $0.7\mu\textrmW$의 레이저 출력을 증폭기 레이저에 입사시켰을 때 최대 25dB을 얻었으며 이때 신호이득의 대역폭이 3 GHz 정도임을 확인하였다. 또한 입력 세기(input power)에 따른 비포화 신호이득의 변화를 측정하고 이때의 포화출력을 측정하였다.

• 대한전기학회논문지:전력기술부문A
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• 제54권12호
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• pp.561-566
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• 2005

This paper introduces a compression technique for power qualify disturbance signal via discrete wavelet transform(DWT). The proposed approach is based on a previous estimation of the stationary component of power quality disturbance signal, so that it could be subtracted from the original signal in order to reduce a dynamic range of signal and generate transient events signal, which is subsequently applied to the compression technique. The compression techniques is performed through the difference signal decomposition, thresholding of wavelet coefficients, and signal reconstruction. It presents the relation between compression efficiency and threshold. It shouts that the wavelet transform leads to a power quality data compression approach with high compression efficiency, small compression error and good de-nosing effect.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.809-811
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• 1993

The load impedance of power lines generally varies with time, areas, and season. Also, the harmonic noises by the power electrical equipments are scattered through the power lines. The received signal level varies with the environment and is not able to detect the PLC(Power Line Carrier) signal. For this reason, it is requried for the signal transmitter to hold the received signal level uniform independently with the variation of the load impedence. In this paper, the power lines are modeled simply and a method keeping the received signal level uniform is suggested through the analysis of the signal transmission characteritics of the PLC coupler using tank circuit.

• Geosystem Engineering
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• 제21권5호
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• pp.251-261
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• 2018

With the urbanization in recent years, the power line interference noise in electromagnetic signal is increasing day by day, and has gradually become an unavoidable component of noises in magnetotelluric signal detection. Therefore, a kind of power line interference noise elimination method based on independent component analysis in wavelet domain for magnetotelluric signal is put forward in this paper. The method first uses wavelet decomposition to change single-channel signal into multi-channel signal, and then takes advantage of blind source separation principle of independent component analysis to eliminate power line interference noise. There is no need to choose the layer number of wavelet decomposition and the wavelet base of wavelet decomposition according to the observed signal. On the treatment effect, it is better than the previous power line interference removal method based on independent component analysis. Through the de-noising processing to actual magnetotelluric measuring data, it is shown that this method makes both the apparent resistivity curve near 50 Hz and the phase curve near 50 Hz become smoother and steadier than before processing, i.e., it effectively eliminates the power line interference noise.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권9호
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• pp.4390-4407
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• 2019

The paucity of pilot signals in Massive MIMO system is a vital issue. To accommodate substantial number of users, pilot signals are reused. This leads to interference, resulting in pilot contamination and degrades channel estimation at the Base Station (BS). Hence, mitigation of pilot contamination is exigency in Massive MIMO system. The proposed Time Shifted Pilot Signal Transmission with Pilot signal Hopping (TSPTPH), addresses the pilot contamination issue by transmitting pilot signals in non-overlapping time interval with hopping of pilot signals in each transmission slot. Hopping is carried by switching user to new a pilot signal in each transmission slot, resulting in random change of interfering users. This contributes to the change in channel coefficient, which leads to improved channel estimation at the BS and therefore enhances the efficiency of Massive MIMO system. In this system, Uplink Signal Power to Interference plus Noise Power Ratio (SINR) and data-rate are calculated for pilot signal reuse factor 1 and 3, by estimating the channel with Least Square estimation. The proposed system also reduces the uplink Signal power for data transmission of each User Equipment for normalized spectral efficiency with rising number of antennas at the BS and thus improves battery life.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.341-343
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• 2005

This paper introduces a compression algorithm for power quality disturbance signal via the discrete wavelet transform, DWT. Algorithm to estimate a time delay from the power quality disturbance signal is proposed. Pseudo-stationary signal is constructed from the estimated time delay. A difference signal or nonstationary signal is obtained by removing a pseudo-stationary signal from a disturbance signal. DWT is applied to a difference signal. The threshold is applied to reduce a number of coefficients. Simulation results show the resonable compression ratio while keep low signal distortion.