• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.25-25
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• 2004

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.215-215
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• 2004

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.449-453
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• 2004

본 연구에서는 고속 광대역의 정보신호를 다중경로 페이딩 환경에서 효율적으로 전송하기 위한 M-ary QAM신호와 OFDM전송방식을 사용할 때 반송파의 주파수 옵셋이 발생하는 동기오차가 수신시스템에 미치는 영향으로 인한 수신 성능을 분석하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.685-691
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• 2003

This paper newly analyzes the effect of the phase noise in the frequency synthesizer on the performance of SFH/M-NCFSK system by standard frequency deviation(equation omitted) when noncoherent FSK demodulation of the square-law detector is considered. We derive the SER in the SFH system and analyze the effect of phase noise on the SFH/M-NCFSK system performance according to the hopping frequency spacing (1/T$\_$h/) and the variation of the standard frequency deviation (equation omitted). The required SNR is about 13.4 dB to meet Ps=10$\^$-3/ when the standard frequency deviation is about 4.0 Hz and the hopping frequency spacing (1/T$\_$h/) in the SFH/2-NCFSK system is 30. So, there is about 2.4 dB power penalty than the phase noise-free system. If the hopping frequency spacing 1/T$\_$h/ is under 30, the error floor may happen and SER considerably grows up. We show that the analytic results closely match with the simulation results.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.15-20
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• 2013

In narrowband communication systems operating in VHF and UHF bands, the performance degradation due to a frequency offset is inevitable. In this paper, we propose a frequency offset reduction scheme using the dual-band FSK modulation for narrowband communications. The proposed scheme not only offer a relatively reliable performance under a severe frequency offsets, but also can obtain a frequency diversity gain in Rayleigh fading channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.364-370
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• 2006

It is required for correct signal detection to accurately maintain the synchronization of frequency and timing in a TDMA system. In this paper, we consider nondecision-aided estimation of frequency offset for the transmission of QPSK signal in a TDMA-based satellite system. The proposed scheme estimates the phases of two parts in the burst and then estimates the frequency offset based on the difference between the two estimated phases. Thus, it can provides performance comparable to that of conventional schemes, while significantly reducing the implementation complexity, The performance of the proposed scheme is analyzed and verified by computer simulation, when applied to a GSM based geostationary earth orbit mobile radio(GMR) system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.4
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• pp.730-736
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• 2008

We proposed and implemented new DDC system which overcomes the difficulties including lack of flexibility of modifications of frequency which is the problem of previous frequence oscillator and synchronization. New DDC system can create frequence in two decimal points. Moreover, due to its usage in adjusting to frequence clock which is required by many consumers, laser distance instrument can reduce its error; thus, implementation of system is capable of high precision distance measurement can be performed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.3
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• pp.93-100
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• 1999

Wide operating range and speed control is needed for wind power generating and a Doubly Fed Induction Generator(DFlG) has good adaptivity for that purpose. Ths paper investigates speed and output stator power control using a grid connected to a DFlG in super-synchronous speed regions, by control of both magnitude and frequency of the voltage fed to the rotor. For the speed control analysis, torque simulation is perforrred whereby the different slip between qJernting rmtor driving frequency and synchronous frequency of M-G system awlied. To keep the output rating of the generator, the exciting frequency and voltage attenuation are arolied.rolied.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.06a
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• pp.153-154
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• 2014

DMB 시스템은 직교주파수분할 (OFDM : Orthogonal Frequency Division Multiplexing) 기반의 전송방식을 사용하기 때문에, 단일 주파수 네트워크 (SFN : Single Frequency Network) 기반 방송망 구축이 가능하다. 이러한 SFN 방송망은 인접 송신기의 시간 및 주파수 동기, 송신소 사이의 거리, 송신 전력의 크기를 고려하여야 하며, 이를 위해서는 먼저 특정 수신점에서 채널 임펄스 응답 (CIR : Channel Impulse Response) 을 분석하여 간섭을 최소화되도록 설계하는 것이 중요하다. 본 논문에서는 DMB 시스템에서 다중경로에 의한 간섭을 효율적으로 측정하는 기법을 제안하고, 모의실험을 통해 제안된 기법의 성능을 검증하고자 한다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1206-1207
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• 2011

하이브리드 발전시스템에서 전압과 주파수제어는 서로 다른 분산전원의 동기화 및 전력제어에 있어서 매우 중요하다. 본 논문에서는 디젤 발전 시스템에서 연료 분사량을 제어하여 주파수를 담당하는 Governor 제어기에 대한 제어 알고리즘을 개발하여 적용함으로써, 연료분사량을 최적화하여 일정한 속도제어를 하고자 한다. 이는 기본 제어기 알고리즘에 전력에 대한 전류 지령치를 첨가함으로서 제어기의 속응성 및 안정도를 개선할 수 있다. 또한 기존 디젤발전기의 부하에 따른 전압 및 주파수 특성을 분석하고, 시뮬레이션 함으로서 본 알고리즘을 검증하였다.