• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.5
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• pp.66-74
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• 2002

OFDM(Orthogonal Frequency Division Multiplexing)is a one of the nst promising digital modulation techniques adapted for Digital audio broadcasting or Digital TV since it is very robust against multipath fading channels. From 1997, since the OFDM technique was considered as the physical layer standard for the high data rate wireless LAN systems in the 5㎓ band, related studies have been studied actively. The key element to implement high data rate wireless LAN system using OFDM technique are IFFT and FFT modules. In this paper, new IFFT and FFT module are designed and implemented using current cut circuit based on the matrix-rounding process for the low-power consumptive operation and high-speed data processing. In addition to, we certify the available operation of the rounded IFFT/FFT module in the AWGN channel by using the BER performance simulation of IEEE 802.11TGa based OFDM modem with rounded IFFT/FFT module.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.300-301
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• 2000

DVD는 CD사이즈의 광디스크에 고화질기 MPEG2 디지털 압축동화를 두 시간이상 수록할 수 있는 기록 및 재생기기로써 최초의 규격서가 1996년 8월에 발행되었다. 650nm의 적색반도체레이저와 개구수 0.6의 대물렌즈를 채용한 광픽업으로 직경 12cm의 단면디스크에 CD-ROM의 약 7배인 4.7GB에서 17GB까지의 용량저장이 가능하다. 변조방식은, DC성분을 억제할 수 있고, 또한 DR(Density Ratio)이 큰 EFM-Plus 변조를 채용하고, 에러정정방식은 32kB를 하나의 블록으로 하는 Reed Solomon Product code이다. File system은, 음성, 화상데이터와 컴퓨터 데이터를 통합할 수 있도록 계층구조로 하고, ISO9669 파일시스템과 UDF파일시스템을 함께 사용하고 있다. (중략)

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.362-369
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• 2007

APSK (Amplitude Phase Shift Keying) digital modulation is characterized by the circular positioning of the transmission symbols in the constellation diagram. Due to such structural characteristics, the peak-to-average power ratio of the APSK modulation is lower than that of the QAM (Quadrature Amplitude Modulation), and the amount of performance degradation over nonlinear channels can be mitigated. The APSK modulation scheme has recently been adopted as satellite communication system standards including the DVB-S2 (Digital Video Broadcasting - Satellite, Version 2). In this paper, a BER (Bit Error Rate) upper bound approximation formula is derived using the channel model with the output power saturation characteristics, and its accuracy is demonstrated. Using the derived formula, the input power level that minimizes the BER is determined. The optimized performance based on the radii ratio of the 16APSK constellation and the channel saturation level is also presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.127-131
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• 2009

본 논문에서는 디지털 통신에서 비트 전송율을 향상 시킬 수 있는 웨이브릿 편이 변조 시스템을 제안한다. 기존의 웨이브릿 편이 변조 시스템에서는 스케일링 함수(scaling function)를 1로, 웨이브릿(wavelet)을 0으로 할당하여 0과 1을 구분하였다. 제안한 방식은 스케일링 함수와 웨이브릿 그리고 이 두 신호를 반전시킨 4개의 반송파를 사용하여 변조한다. 즉, 웨이브릿은 00, 반전된 웨이브릿은 01, 스케일링 함수를 10, 반전된 스케일링 함수를 11로 할당하여 비트 전송률을 2배로 향상시키고자 한다. 복조시에는 4개의 상관기를 이용하여 원래의 2진 데이터(2비트)를 복원하였다. 모의실험 결과 제안한 방식이 기존의 웨이브릿 편이 변조 시스템에 비해 전송효율이 2배 향상되었음을 알 수 있다.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.215-224
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• 2003

This paper presents an electronic ballast using a novel complex modulation method for the metal halide lamp. The proposed modulation method, which has a modulating signal of swept complex frequency, can eliminate the acoustic resonance more effectively than the conventional modulation method, which has a modulating signal of constant frequency. For the purpose of future application specific integrated circuits (ASIC). the controller of the proposed ballast has been designed only with erasable programmable logic devices (EPLDs), but without a microprocessor. In this paper, detailed proposed modulation schemes are described and experimental results on the proto type 150W metal halide lamp ballast with the proposed modulation method ate discussed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.9
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• pp.2009-2019
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• 2013

In this paper, we propose an automatic modulation recognition algorithm based on cyclic moment and new modified cumulant for analog and digital modulation signals. It is noteworthy that each modulated signal has different cycle frequency characteristics according to its order of cyclic moment. By means of this characteristics as classification features, various modulated signals can be efficiently classified. Also, to identify modulated signals having the same cycle frequency characteristics, we take advantage of the additional classification factors such as variations of envelope and phase as well as modified cumulant. The proposed algorithm was evaluated by considering the number of symbols, SNR, and frequency offset. In the simulation condition where the number of gathered symbols was about 819, and SNR and frequency offset were above 10dB and below 25%, respectively, the average accuracy of the proposed algorithm was more than 95%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1041-1046
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• 2004

Orthogonal frequency division multiplexing(OFDM) is becoming the chosen modulation technique for wire and wireless communications with fast data rate because of good spectral efficiency and sufficient robustness of fading channel. Digital Video Broadcating is using OFDM to modulate. But Digital Video Broadcating has performance degradation in moving reception according to DOA(Direction of Arrival). The purpose of this paper is to improve reception performance using array antenna in environment with doppler effect.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.233-236
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• 2005

국내외적으로 M/W 중계용 주파수 대역은 3${\sim}$30GHz 대역이다. 그러나 갈수록 늘어나는 서비스와 전송용량의 증대로 인해 주파수 부족현상이 일어나는 추세이다. 이에 대한 방안으로 주파수 재배치에 관한 문제가 대두되고 있다. 이동방송 중계용 링크인 FPU 링크는 차후 다른 주파수 대역으로 이전시 이전의 링크에서 사용되었던 시스템 제원을 토대로 필요한 대역에 대해 다양한 변조방식으로 시뮬레이션 평가 후 이용채널 개수 및 이전 가능 여부등과 같은 조치가 수행되어져야 한다. 본 논문에서는 M/W 대역 휴대용 디지털 무선전송 시스템으로써 디지털 FPU 링크 시스템을 모델링하고 이동환경에서 발생하는 도플러 천이 효과를 고려한 Clark & Gans 페이딩 채널 모델을 고려하여 페이딩의 영향에 따른 시스템 성능을 분석하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1769-1776
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• 2000

In this paper a new method is proposed to identify a modulation method in the case of unknown digitally modulated input signals. The proposed identification method is implemented with an artificial neural network which is based on characteristic feature extracted from the instantaneous amplitude the instantaneous phase and the instantaneous frequency of the input signals. The proposed method was simulated with 9 type signals (ASK2, FSK2, FSK4, PSK2, PSK4, PSK8, QAM8, QAM16) in a noisy communication environment. The results show that the artificial neural network can accurately recognize all kinds of patterns.

• Journal of Broadcast Engineering
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• v.24 no.3
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• pp.485-494
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• 2019

A software-driven real-time frequency de-modulator is implemented with the aid of universal-serial-bus (USB) type software defined radio dongle. An analog stereo frequency modulation (FM) broadcast signal is down-converted to the basedband analog signal then converted to digital bit streams in the USB dongle. Computer software such as Matlab, Python, and GNU Radio manipulates the incoming bit streams with the technique of digital signal processing. Low pass filtering, band pass filtering, decimation, frequency discriminator, double sideband amplitude demodulation, phase locked loop, and deemphasis function blocks are implemented using such computer languages. Especially, GNU Radion is employed to realize the real-time demodulator.