• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.2
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• pp.77-83
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• 2011

In this paper, we present the design procedure of the synchronizer and the demodulator of a 13.56MHz RFID PJM tag, which was standardized in ISO 18000-3 mode 3. We optimize the algorithms in order to minimize the number of registers and implement them based on international standard. The designed module is simulated by Modelsim and FPGA. The synchronizer is composed of 3 correlators that is implemented by 1,024(16bit ${\times}$ 64cycle) registers. The demodulator is composed of 2 correlators that is implemented by 128(2bit ${\times}$ 64cycle) registers. The simulation performed with the demodulator integrated with the synchronizer shows that it works at about 87% success rate with the test data of SNR -2dB and 100% with those of SNR 4dB.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.178-182
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• 2000

During the past five years, there has born tremendous interest worldwide in the possibility of exploiting chaos in wideband communication systems. Many different demodulation techniques have been proposed up to date. They can be divided into two basic categories. In the first approach, like the conventional coherent demodulation techniques, the chaotic signal has to be recovered from the received noisy signal by synchronization. However, the chaotic synchronization techniques published to data are so sensitive to the channel noise and distortion that these techniques can not be used in radio communications. In the second approach, the demodulation is carried out nonsynchronization. This paper surveys the different chaotic communication techniques that can be implemented nonsynchronization and compares the threshold and BER of the different methods. Finally, FM-DCSK is introduced the first step for apply to wideband chaos digital CDMA, where the data is not limited by the inherent nonperiodic property of the chaotic signal.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.43-50
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• 2004

For the simultaneous measurement of strain and damage signal a fiber Bragg grating sensor system with a dual demodulator was proposed. The dual demodulator is composed of a demodulator using a tunable Fabry-Perot filter measuring the low-frequency signal with large magnitude such as strain and the other using a passive Mach-Zehnder interferometer detecting the high-frequency signal with small amplitude such as impact or damage signal. Using the proposed fiber Bragg grating sensor system, both the strain and damage signals of a cross-ply laminated composite beam under tensile loading were simultaneously measured. The strain and damage signals detected by single fiber Bragg grating sensor showed that sudden strain shifts were accompanied with vibration at a maximum frequency of several hundreds of kilohertz at the instant of matrix crack propagation in the 90 degree layer in composite beam.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.461-467
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• 2022

Sonobuoy is a disposable device that collects underwater acoustic information and is designed to transmit signals collected in a particular area to nearby aircraft or ships and sink to the seabed upon completion of its mission. In a conventional sonobouy signal transmission and reception system, collected signals are modulated and transmitted using techniques such as frequency division modulation or Gaussian frequency shift keying, and received and demodulated by an aircraft or a ship. However, this method has the disadvantage of the large amount of information to be transmitted and low security due to relatively simple modulation and demodulation methods. Therefore, in this paper, we propose a method that uses an autoencoder to encode a transmission signal into a low-dimensional latent vector to transmit the latent vector to an aircraft or ship and decode the received latent vector to improve signal security and to reduce the amount of transmission information by approximately a factor of a hundred compared to the conventional method. As a result of confirming the sample spectrogram reconstructed by the proposed method through simulation, it was confirmed that the original signal could be restored from a low-dimensional latent vector.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.553-556
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• 2001

본 논문은 불완전한 휘도/색신호 분리로 인해 복조된 NTSC 칼라 TV신호의 휘도와 색차신호의 경계(edge)에서 나타나는 dot 패턴을 제거하는 2차원 필터에 대한 것이다. 제안된 필터는 휘도와 색차신호의 천이영역 검출신호와 dot 패턴 검출신호에 따라 직렬(cascade)로 연결된 수평-수직방향 저역통과필터의 차단주파수를 조절함으로써 dot 패턴을 감소시킨다. 제안 방식의 성능을 검증하기 위하여 현재 가장 많이 사용되는 NTSC 디코더 칩인 BT835과 SAA7113H을 이용하여 복조된 휘도와 색차신호에 적용한 결과 영상신호가 변화를 갖는 경계 영역에서 발생한 dot 패턴과 불완전한 복조로 인해 발생하는 평탄영역에서의 dot 패턴이 제거되었음을 확인할 수 있었다.

• Information and Communications Magazine
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• v.16 no.10
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• pp.64-74
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• 1999

무선 채널에서 제한된 주파수 대역폭을 최대로 활용하여 비디오 데이터를 전송하기 위해서는 고효율의 변복조 기법, 페이딩 보상 기업 및 효율적인 오류 정정 기법이 요구된다. 본 고에서는 RF 주파수가 2GHz 대역이고 주파수 대역폭이 200 KHz를 갖는 TDMA 방식에 의한 WLL 모뎀(이하 AdWiLL$^{TM}$이라 한다) 설계에 대하여 기술한다. AdWiLL$^{TM}$모뎀의 핵심 기술로는 채널 특성을 실시간으로 분석하여 최적의 송수신 조건을 결정하는 channel probing 기술, 페이딩 환경에서 다중 레벨 QAM변복조를 가능하게 하는 적응출력제어 기술, WLL전파 환경과 서비스가 고려된 연접 부호(concatenated coding)를 통한 순방향 오류 정정(FEC) 기술, 송수신 성능 향상을 위한 범포밍 기술이 포함된다. 구현된 모뎀으 고정 무선 채널 환경에서 16 채널에서 32Kbps ADPCM 음성 신호를 동시에 송신할 수 있으며, 협대역 ISDN에서 제공하는 전송속도로 비디오 데이터의 전송이 가능함을 보였다.

• Journal of Sensor Science and Technology
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• v.9 no.6
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• pp.416-423
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• 2000

A new demodulation technique which can be used for the fiber optic acoustic sensor system using Sagnac interferometer is described. The theoretical limitation in dynamic range of the quadrature demodulation technique can be removed by the proposed BPSK(Binary Phase Shift Keying) demodulation technique. Full demodulation of input acoustic signal is possible with just simple electronics by eliminating the necessity of the high frequency phase modulation. This technique is suitable for digital signal processing of fiber optic sensor systems and can be applicable for other interferometers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9C
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• pp.841-847
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• 2009

In this paper we propose a high-performance Hybrid ARQ scheme employing Chase combining based on LDPC (Low-Density Parity-Check) codes. The proposed scheme uses symbol mapping diversity and turbo demodulation to improve decoding performance. We analyze the performance of the proposed scheme by EXIT (EXtrinsic Information Transfer) chart and compare its performance with several symbol mappings.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1316-1319
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• 1996

진폭변조(AM) 신호를 검파기하기 위한 디지탈 시스템을 실현하기 위해서는 보통 변조된 신호의 최대주파수의 2배 이상되는 주파수로 샘플링해야만 한다. 이러한 경우에 반송파가 커지면 처리할 데이터가 많아지기 때문에 디지탈 시스템이 복잡해져 실시간 처리가 어렵게 된다. 본 연구에서는 샘플링 주파수를 대역폭을 기준으로 하여 낮출 수 있는 유용한 두 종류의 복조시스템을 제안하였다. 또한 undersampling한 복조회로에 대한 특성 및 오차를 해석하고 검토하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.931-932
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• 2009

개인용 비디오 녹화기는 하나의 채널을 통해 수신된 스트림에 대해서만 재생 또는 하드 디스크에 저장할 수 있도록 구성되어, 다른 채널을 시청하면서 특정 채널의 방송을 저장할 수 없거나 2개의 튜너와 복조기를 탑재하여 녹화를 하면서 다른 실시간 방송을 시청할 수는 있으나 전자 프로그램 가이드를 이용하여 개인용 방송 편성을 구현하는데 어려움이 있었다. 본 논문에서는 종래 기술의 제반 단점과 문제점을 해결하기 위한 것으로, 개인용 비디오 녹화기의 기본 어플리케이션의 하나인 전자프로그램 가이드에서 현재 녹화되고 있는 채널 이외의 방송을 시청할 수 있도록 멀티 복조기를 탑재한 개인용 비디오 녹화기를 이용한 방송 편성 방법을 제안한다.