• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 A
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• pp.71-74
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• 2003

The signal processing algorithm for a PSD(Position Sensitive Detector) using amplitude modulation/demodulation is addressed in this paper. Dark currents and external noises such as daylight and fluorescent lights are eliminated by using amplitude modulation/demodulation and a low pass filter. The proposed amplitude modulation/demodulation method for a PSD sensor is compared with pulse amplitude modulation method. The proposed amplitude modulation is proved to be more accurate and robust than PAM method by analysis and experiments. Multiple measurements using one PSD sensor by amplitude modulation/demodulation is also addressed. The Power variation of light source is compensated by normalization process using a divider.

• 전자공학회논문지A
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• 제31A권7호
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• pp.29-35
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• 1994

The performance of continuous phase modulation signals is well known for the coherent demodulation. But the carrier recovery circuits of the coherent receiver have long acquisition time and the receiver experiences high error floors for fading channels. In this paper, we propose the differential demodulation of 2-h continuous phase modulation signals. The sets of modulation indices of 2-h phase codes adequate to the differential demodulation for differentially encoded input are obtained and the average bit error probability in Additive White Gaussian Noise environments is derived and analyzed.

• Journal of information and communication convergence engineering
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• 제6권2호
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• pp.192-197
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• 2008

High-speed harmonic optical modulation-demodulation schemes are presented and a possibility of the schemes for applying to high-speed light wave transmission system is tested at microwave frequency range. An example of this concept is as follows : Light wave is modulated succeedingly through cascaded optical modulators by a sub-carrier to produce a modulated light wave at harmonic frequency which is higher than the feasible frequency of the individual modulators. For demodulation of the base-band signal, the high frequency optical sub-carrier is down-converted by the same kind of optical modulator with the same concept of harmonic modulation.

• 한국통신학회논문지
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• 제41권12호
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• pp.1736-1738
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• 2016

고차변조와 고효율 채널부호를 사용하는 통신시스템에서는 지수함수의 합 로그 연산을 수반하는 다량의 대수우도비 산출이 필수적이며 이의 근사화 기법에 따라 링크 성능이 좌우된다. 본 논문에서는 신규 근사화 기법을 복조기와 복호기에 결합하여 적용하고 복잡도를 분석하며 모의실험을 통해 도출한 결합 성능을 분석한다.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권7호
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• pp.399-406
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• 2000

We propose an nonlinear demodulation algorithm for undersampled multicomponent AM(Amplitude Modulation), FM(Frequency Modulation) and AM-FM signals. First, we derive respectively undersampling frequency of the AM, FM and AM-FM using undersampling scheme, and separate respectively monocomponent signals from multicomponent signals using periodic algebraic separation algorithm. In this case augmented separation matrix is very regular and sparse, it has a special structure. The proposed demodulation algorithm detects respectively message signals of the IA(Instantaneous Amplitude) and IF(Instantaneous Frequency) from descrete monocomponent AM, FM and AM-FM signals with an undersampling frequency to be controllable. Verifying the RMS(Root Mean Squares) errors of the detected signals, we show that the performance is excellent.

• 전자공학회논문지B
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• 제33B권7호
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• pp.86-98
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• 1996

Modulation and demodualtion circuits of chaos frequency shift keying have been implemented using chua's circuits. The modulatin circuit, which is designed ot perform the frequency-doubling by coupled synchronization wihtout changing the intrinsic characteristics of its two chaos signals generated, modulates the digital input signals. The demodulation circuit detects the digital input signals form carrier by drive synchronization. these circuits, which are simplest until now and have no restriction to their digital input amplitudes, perform the aimed functions.

• 전자공학회논문지A
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• 제33A권4호
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• pp.1-10
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• 1996

As the demand for high-speed and wirelesstransmission of information is rapidly increasing, spectrally efficient digiral radio modulation and demodulation scheme is preferred. In this paper, we have studied the signal generation, demodulation and performance evaluation of spectrally efficient QAM signals in a wireless channel environment. We propose differential modulation and demodulation scheme for QAM in rayleigh fading channel. First, formulas for theerror probability of proposed QAM scheme are derived over QWGN channel. Second, we evaluate the performance of the proposed QAM scheme in rayleigh fading environment through computer simulation, and confirm that it shows much better performance compared to that of conventional QAM scheme.

• 한국정보통신학회논문지
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• 제10권5호
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• pp.851-856
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• 2006

본 논문에서는 단일 PLL을 사용하여 400MHz 대역의 트랜시버를 구현하였다. 일반적인 트랜시버의 경우, 송수신부에 각각 한 개의 PLL과 수신부에 2단의 믹서를 사용하여 구현되어진다. 이러한 구성 은 트랜시버의 가격과, 부피에 상당히 큰 영향을 미친다. 본 논문에서는 기존의 방식을 탈피하여 단일 PLL방식의 데이터 전송용 특정 소출력 무선기기의 송, 수신단의 회로설계, 제작 및 특성측정 연구를 하였다. 설계된 트랜시버의 주파수 대역은 424.7-424.95MHz이고, Low Side Injection방식을 사용하여 450KHz의 IF 주파수로 변환(Conversion)하였고, 반이중 (Semi duplex Communication) 통신방식, PLL Synthesized, 21 Channel, 12.5KHz Channel Bandwidth, FSK Modulation/Demodulation방식을 사용하였다.

• 방송공학회논문지
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• 제4권1호
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• pp.1-11
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• 1999

본 논문은 웨이브릿 패킷 기저함수에 기초한 직교 다중화 변복조 기법을 소개하고 특히 시스템 설계자 입장에서 전송 신호의 특성을 시간-주파수 공간에서 신호 파형을 설계하고 주어진 채널 특성에 맞게 설계할 수 있는 구조를 제공하는 Wavelet Packet Modulation 기법을 기술하였다. 다차원 시그널링 방법을 기존의 QAM, Multi-tone 변조방식과의 공통성과 차이점을 대비하였다. 또한 직교 기저함수 집합을 만들어 시간-주파수 공간을 임의적으로 Partitioning 하고 협대역 톤 잡음과 임펄스 잡음 채널에 더 잘 적응할 수 있는 구조를 찾는 방법을 튜닝 알고리듬을 사용하여 기술하였다. 튜닝 알고리듬의 실험적인 결과는 WPM 변조 방식이 협대역 간섭과 임펄스 잡음에 대하여 기존 방섹이 비해 우수한 성능을 갖음을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권4호
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• pp.767-783
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• 2013

This paper aims at designing a selective demodulation scheme based on Log-likelihood Ratio threshold (SDLT) instead of the conventional adaptive demodulation (ADM) scheme, by using rateless codes. The major difference is that the Log-likelihood ratio (LLR) threshold is identified as a key factor to control the demodulation rate, while the ADM uses decision region set (DRS) to adjust the bit rate. In the 16-QAM SDLT scheme, we deduce the decision regions over an additive white Gaussian channel, corresponding to the variation of LLR threshold and channel states. We also derived the equations to calculate demodulation rate and bit error rate (BER), which could be proven by simulation results. We present an adaptation strategy for SDLT, and compare it with ADM and adaptive modulation (AM). The simulation results show that our scheme not only significantly outperforms the ADM in terms of BER, but also achieves a performance as good as the AM scheme. Moreover, the proposed scheme can support much more rate patterns over a wide range of channel states.