• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1528-1538
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• 2016

Common data link systems are designed to transmit the imaginary and signal intelligence data at long distance air-ground line of sight(LOS) link. In this paper, we analyze the received power variation according to the communication distance of the common data link using curved earth 2-Ray model suitable for received signal power analysis of long distance air-ground wireless channel. We propose optimal elevation angle control method of the receiving antenna to reduce a power variation caused by ground-reflected wave. Proposed method can get additional link margin compared to the conventional method without any additional hardware performance enhancement.

• KIEE International Transactions on Power Engineering
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• v.5A no.2
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• pp.138-143
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• 2005

During faults, the voltage and current signals available to the relay are affected by the decaying dc component and harmonics. In order to make appropriate and accurate decisions, most of the relaying algorithms require the fundamental frequency phasor information that is immune to decaying dc effect and harmonics. The conventional Fourier ph as or estimation algorithm is affected by the presence of decaying-exponential transients in the fault signal. This paper presents a modified Fourier algorithm, which effectively eliminates the decaying dc component and the harmonics present in the fault signal. The decaying dc parameters are estimated by means of an out-of-band filtering technique. The decaying dc offset and harmonics are removed by means of a simple computational procedure that involves the design of two sets of Orthogonal digital OFT filters tuned at different frequencies and by creating three off-line look-up tables. The technique was tested for different decay rates of the decaying dc component. It was also compared with the conventional mimic plus the full cycle OFT algorithm. The results indicate that the proposed technique has a faster convergence to the desired value compared to the conventional mimic plus OFT algorithms over a wide range of decay rates. In all cases, the convergence to the desired value was achieved within one cycle of the power system frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.11
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• pp.2228-2237
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• 1994

This paper describes the development of a Ku-band ($12.25GHz\sim12.75GHz$) SSPA intended as a replacement for TWTAs used in communication satelite transponder. The power stage of the amplifier consists of tow intrmally matched 8W FET divices combined using the branch-line coupler. To operate this stage, the drive stage has been designed with intermally matched 2W, 4W, 8W FET and two medium power FETs. The entire amplifier is made up by a aluminum chassis housing both the RF circuit and the bias circuitry. A regrlator/sequencing circuitry is used for FET biasing. The amplifier results implemented in this way show $41\pm0.3dB$ small-signal gain, 15W saturation power, a typical two tone $IM_3=-21.5dBc$ with single carrier backed off 5dB from saturation, $2^*/dBmax$ AM/PM conversion, and $3.47\pm0.25nsec$ group delay.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1347-1349
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• 1995

Insulators contaminated by salt particles may cause flashovers in humid climate or light rain. Therefore, the quantity of salt on insulators should be monitored not to exceed a critical value. We propose a new remote sensing technique to measure the quantity of salt on insulators of power systems. The amount of the salt is measured from the intensity of the spontaneous emission from the sodium atoms. In this paper, a compact remote on-line salt-meter composed of Q Switch pulsed Nd:YAG laser and emission signal detection system will be introduced. And as the first result of this study, the operating characteristics of our developing laser system is also introduced.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1712-1714
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• 2001

This paper deals with the development and application of an inner corrosion detector for the ACSR(Aluminum Conductor Steel Reinforced) power lines. The detector runs on an ACSR power line and inspects the inner corrosion of the conductor using the technology of the nondestructive eddy current test. It is consists of an ECT sensor, signal processing units, a RF transmitter/receiver, and etc.. The experimental result through field tests shows the detector can efficiently find both the zinc and aluminum loss of ACSR power lines.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.11
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• pp.583-588
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• 2004

We stabilized the frequency and power of a high voltage excited CW CO2 laser on the peak of the Doppler broadened gain curve using the photoacoustic effect generated from the laser itself. The photoacoustic signal is directly coupled from an radio frequency discharge chamber via a capacitor microphone into a detector and a lock-in stabilizer. The frequency stability is estimated to be better then 1.2×10/sup -7/ at the transition P(20) line. The stabilized output power variation was reduced to from 77 % to 3.3 %.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.149-151
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• 2005

This paper deals with the novel control algorithm of single-phase hybrid active power filter for the compensation of harmonic current components in nonlinear R-L load with passive active power filters. To construct two-axes coordinate, an imaginary second phase was made by giving time delay to line current. In this proposed method, the new signal, which was the delayed through the filtering by the phase-delay property of low-pass filter, is used as the secondary phase. Because two phases have different phase, instantaneous calculation of harmonic current is possible. In this paper, a reference voltage is created by multiplying gain of filter by compensation current using the rotating reference frames that synchronizes with source-frequency, not applying to instantaneous reactive power theory which has been used with the existing fixed reference frames. This paper shows the experimental results, which provide a high accuracy and extremely fast response of single-phase hybrid active Bower filter under the operation with the proposed control method.

• Journal of the Optical Society of Korea
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• v.1 no.2
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• pp.110-115
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• 1997

We report effcient cascaded Raman generation and signal amplification at 1.3.mu.m achieved in a ring resonator constructed solely from fiber components, i.e. fusion WDM couplers. Low-loss single-mode fiber with moderate $GeO_2$ content (18 mole %) is used as an active medium and pumped by a Nd:YAG laser at 1.064.mu.m. In a resonant cascaded geometry, this generates the third Stokes line at 1.24.mu.m, which acts as a pump for signal wavelength around 1.3.mu.m. A DFB laser operating at 1.315.mu.m is used to provide an input signal. An output signal powers up to 20 dBm (100 mW) with a 28 dB Raman gain are attained, where the Nd:YAG pump power is 3.4 W. It is also shown experimentally that it is important to use optical filters to suppress feedback from the resonator, permitting high Raman gain and good signal quality.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.728-732
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• 2010

GIS(Gas insulated switching gear) is power equipment with excellent dielectric strength and is economy merit in high confidence and stability. Recently, because equipment of GIS was occurring problem of confidence used for a long time, partial discharge on-line diagnosis systems have been importantly recognized. Partial discharge (PD) detection is an effective means for monitoring and evaluation of dielectric condition of gas insulated system (GIS). The ultra-high-frequency (UHF) PD detection technique can detect and locate the PD sources inside GIS by detecting electromagnetic wave emitted from PD source. Therefore, real-time diagnostic system using UHF detection method has been developed for this application is being expanded gradually. However, the signal of partial discharge occurring in SF6 gas is very weak and susceptible to external noises which mainly consist of PD in air. Thus, it is important to distinguish the PD in SF6 gas more sensitively from the external noises. Unfortunately, these external noise signals and the partial discharge signals have very similar characteristics. Therefore, to solve this problem, we need the signal processing method for distinguish partial discharge signals with external noise signals for improvement of SNR(signal to noise ratio) and sensitivity. In this paper, we proposed internal signal processing method for removing external noise signals with built-in pre.amplifier and frequency conversion circuit.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.7
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• pp.1287-1294
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• 2001

As size of waveform is very small, ECG(electrocardiogram) signal is difficult to analyze for noise which is occurred when it measures. In order to obtain ECG clearly, it must eliminate that power line interference, baseline wandering, noise of muscle constriction. In ECG, the worst problem which is recorded signal of ECG is the baseline wandering elimination, which is occurred by rhythm of respiration and muscle constriction of part from attaching to an electrode. Such the baseline is roughly irregular wandering and shaking up and down therefore the part of the baseline wandering elimination is very important because it is difficulty of ECG diagnosis. In this study, as implementation of real-time signal processing digital filter it is applicable to analyze patient's heart disease by way of design of the baseline wandering elimination system.