• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1281-1283
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• 1995

In this paper, we develop a prototype of the Optical SCM transmission module. This module is possible to application to electric facilities for control and measurements. Transmission channel number is two channels, namely, image and digital signal. In the image transmission, modulation method is AM, baseband signal is NTSC video signal and demodulation use PLL. Modulation of digital signal is QPSK, 1.544Mbps and demodulation use PLL. First, we calculate theoretical analysis about RF and Optical link in the transmission. This calculation is well correspond with practical system and transmission experiment is excellent, but this is only two channel model. And now, we plan to multichannel transmission to measure intermodulation, frequency assignments and optimal channel numbers et al.

• The Journal of the Acoustical Society of Korea
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• v.10 no.2
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• pp.44-51
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• 1991

In this paper, we have studied the FM-extended broadcasting which makes the enhancement of stereo signal-to-noise ration by utilizing the compression technique and quadrature moduation method of standard subcarrier signal in transmitter station, and corresponding demodulation method and expansion technique in receiver system. The proposed system is completely compatible with the conventional FM stereo system. We have confirmed the validity of the proposed method by implementation of transmitter/receiver system including quadrature modulation/demodulation and companding system.

• ETRI Journal
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• v.37 no.1
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• pp.1-10
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• 2015

A blind hopping phase estimator is proposed for the demodulation of received signals in frequency-hopping spread spectrum systems. The received signals are assumed to be bandwidth limited with a shaping filter, modulated as frequency modulation (FM) or binary frequency shift keying (BFSK), and hopped by predetermined random frequency sequences. In the demodulation procedure in this paper, the hopping frequency tracking is accomplished by choosing a frequency component with maximum amplitude after taking a discrete Fourier transform, and the hopping phase estimator performs the conjugated product of two consecutive signals and moving-average filtering. The probability density function and Cramer-Rao low bound (CRLB) of the proposed estimator are evaluated. The proposed scheme not only is very simple to implement but also performs close to the CRLB in demodulating hopped FM/BFSK signals.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.91.2-91.2
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• 2013

The Korean Solar Radio Burst Locator (KSRBL) is a solar radio spectrograph observing the frequency range between 0.245-18 GHz with the capability of locating the wideband gyrosynchrotron bursts. Its calibration process consists of antenna calibration, flux calibration, and demodulation. Antenna calibration is to determine the position, the width, and the peak value of the beam, flux calibration is to determine the conversion factor between the measured unit to the Solar Flux Unit (SFU), and demodulation is to determine the burst position and remove the modulation pattern. We introduce the current calibration software and some information that potential users may concern.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.870-873
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• 1991

In this paper, We present demodulation and synchronization method of phase shift keying signal using Double Frequency Vector Technique for Reference Vector. 2nd Harmonic Vector for Reference Vector is utilized in discriminating between noise and carrier signal, and in producting correlation value for data bit logical level. And we applied this demodulator to Automatic Meter Reading System being communicated with electric distribution power lines.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.2
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• pp.137-144
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• 1991

A new demodulation scheeme for differentially encoded GMSK signal is introduced and described. In the proposed differential detection method, the signal is sampled at the center of the time slot, at which the effect of the intersymbol interference is relatively smaller than the edge of the time slot. The proposed differential detector takes this adbantate. The error rate performance of the differential detector has been numerically calculated in the fast fading encountered in the land mobile radio channels. A comparison of performance with the differential detector for MSK signal is given. Finally the possibility of improving performance employing nonredudant error correction is studied.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.11
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• pp.1095-1102
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• 1991

In this paper, we proposed the differential demodulation technique of 2-h CPM and analyzed its error performances. We derived the sets of modulation indices of 2-h phase codes adequate to the differential detection. The power spectra of 2-h CPM signals with various sets of mudulation indices are illustrated and compared, Besides, the error performances for the differential detectors are calculated and detectors using Viterbi algorithm are compared and analyzed by computer simulations.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.11
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• pp.16-24
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• 1997

In order to prevent the presence of the residual phase difference at the discriminator output by the existing AFC techniques, we propose a new automatic frequency control(AFC) tracking algorithm for QPSK demodulation at the digital direct broadcasting satellite(DBS) receiver, which we call a rotational decision-directed AFC(RDDAFC). The RDDAFC rotates the decision boundary for the kth received symbol by the frequency deterctor output of the (k-1)th received symbol. Tracking performances of carrier frequency offset by the proposed RDDAFC algorithm are evaluated through computer simulations under the practical DBS channel conditions with a carrier frequency offset of 2.3MHz when S/N equals 2dB. Test results show that the total pull-in time of the RDDAFC is 1.697msec for 10$^{-3}$ SER before forwared error correction at the receiver.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.179-193
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• 2016

In power quality monitoring, voltage fluctuation is one of the power quality problems, which cause light flickers. To determine the flicker severity, the flicker meter concept was developed in an IEC 61000-4-15 standard. Generally, voltage fluctuations are described as an amplitude modulation(AM). The flicker meter of IEC 61000-4-15 as an international standard for flicker measurement recommends square demodulation method to detect flicker signals from voltage fluctuation signals. This paper suggests a new effective method using filter bank to detect and estimate flicker signals, which do not need square demodulation. For the accurate detection of flicker signals, the filter bank is designed with a full consideration of the spectrum characteristics of voltage fluctuation signals described as AM. The frequency and magnitude of the detected flicker signals are estimated using recursive method. Computer simulations were performed on synthesized signals to prove validity of the proposed method.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.185-189
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• 2005

For the simultaneous measurement of strain and vibration signal, a fiber Bragg grating sensor system with a dual demodulator was proposed. One demodulator using a tunable Fabry-Perot filter could measure low-frequency signal such as strain and the other demodulator using a coarse wavelength division multiplexer could detect high-frequency signal such as vibration signal using intensity demodulation method. In order to measure strain and vibration of the composite main wing model under static loading a real time monitoring program was developed. Also using intensity demodulation of CWDM, sensitivity and resolution at high frequency vibration were evaluated.