• Journal of Korea Multimedia Society
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• v.3 no.6
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• pp.625-632
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• 2000

This paper proposes an adaptive multislot allocation algorithm in order to achieve large system capacity and higher throughput data transmissions. The proposed system is the combination of the slow adaptive modulation system, in which the base station dynamically a signs optimum modulation parameters measuring the CNR(carrier to noise power ratio) of each transmission terminal, and the multislot allocation scheme, in which the base station flexibly allocates an appropriate number of TDMA data slots according to the instantaneous load conditions. Computer simulations confirm that the proposed system can tremendously improve average message delay characteristics in comparison with the conventional fixed slot allocation method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1241-1246
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• 2005

This paper proposes an adaptive multislot allocation algorithm in order to achieve larger system capacity and higher throughput data transmissions. The proposed system is the combination of the slow adaptive modulation system, in which the base station dynamically assigns optimum modulation parameters measuring the SNR of each transmission terminal, and the multislot allocation scheme, in which the base station flexibly allocates an appropriate number of TDMA data slots according to the instantaneous load conditions. Computer simulations confirm that the proposed system can tremendously improve average message delay characteristics in comparison with the conventional fixed slot allocation method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.7
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• pp.679-686
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• 2002

Based on the alternating series expansion of error probability function due to phase noise in PSK systems, the performance evaluations for Tikhonov and Gaussian probability density functions were performed in this paper. The range of the signal-to-noise ratio of recovered carrier signal which provides the same dependency between the error performances by Tikhonov function and Gaussian function was analyzed via loss evaluation due to phase noise. The phase noise with 1/f$^2$ characteristic was generated based on the relationship of the phase noise spectral density and the modulation index for frequency modulation signal. Using the generated phase noise as the input signal for digital satellite communication receiver, the performance losses due to the phase noise were measured and evaluated with the analyzed performance characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.2
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• pp.122-136
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• 1986

In this paper, the new modulation system, the digital phase-frequency hybrid modulation system is proposed for mobile radio communications. The error rate and the outage equation of PFSK(Phase-Frequency Shift Keying) signal transmitted through the fading channel has been derived considiering deversity techniques. The error rate and the outgae rate performances of PFSK system have been evaluated and shown in figures in terms of carrier-to-noise power ratio(CNR), fading figure, numbers of diversity branches, correlation coefficient among the diversity branches. And the performance of PFSK system is superior to that of QDPSK system. And by using diversity techniques, system performances can be improved 13dB above in CNR.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.24-36
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• 2002

It is important to use frequency resource effectively to support much more users, to maximize the DS-CDMA system performance. In this paper, we use MPSK, QAM, MFSK and PR coder as a baseband modulation method for DS-CDMA system. Increasing user's number, we compare the performance of each system using different baseband modulation method, by expecting BER performance. BPSK has generally good performance, in case of low power operation of terminal 8FSK has excellent performance relatively, PR has excellent performance when high power operation of terminal and also good for situation of excessive user's number. QAM is not suitable for DS-CDMA system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.2029-2036
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• 2014

The performance analysis of optoelectronic oscillator(OEO) based on a directly modulated semiconductor laser was theoretically achieved. First, the analysis was performed on the open response of the key components that constitute the OEO loop. Using the results, we simulated the open-loop characteristics of the OEO loop. By combining oscillation conditions of loop oscillator in addition to the open-loop magnitude and phase responses, theoretical performance analysis such as OEO's oscillation frequency, spurious tones and phase noise was successfully completed.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.313-318
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• 2005

We propose an active stabilization method for the receiver of NRZ-DPSK transmission. The 1-bit delayed Mach-Zehlder interferometer is thermally controlled to maintain the largest DC component power ratio between the constructive and destructive output ports, for the optimum transmission condition. This method is very cost effective since no additional components are required. Experimental results show that the proposed scheme guarantees error free performance even when there was ~ 1 GHz optical carrier frequency fluctuation in 10 Gbps transmission.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.223-223
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• 2009

압전 변압기(PT)는 전자제품의 전원 공급 장치에서 마그네틱 변압기의 대안으로서 소형화와 높은 절연 내압의 특성 등을 가지고 있다. 이는 시스템의 소형화와 절연 특성을 크게 높일수있는 장점을 지니고있다. 본 논문에서는 고정주파수 펄스폭 변조 압전 변압기의 구동을 위해, AM modulation을 이용한, 한 점에서의 센싱을 통한 위상제어와 펄스폭 변조 제어를 제안하였다. 이를 위해 EDF 소신호 분석을 하였고, 루프를 설계하여 검증하여 보았다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.193-196
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• 1999

본 논문은 음향 임펄스를 모델링하는데 코사인 변조된 필터 뱅크와 Decimation을 이용하여 수렴 속도를 개선하는 방법을 제안하고 이를 잡음제거에 응용하였다. 제안된 구조는 입력신호를 필터뱅크를 이용하여 각 서브밴드로 분할한 후 필터 입력신호의 고유벡터의 최대값과 최소값의 비를 줄이고 필터의 탭수를 줄이기 위해서 decimation을 행한다. 그리고 서브밴드대역의 샘플링 주파수를 낮추어 신호 스펙트럼을 확장시켜 이를 적응필터에 입력하여 수렴속도를 향상시켰다. 실험 결과, Colored잡음의 경우 LMS 알고리즘보다 제안된 방법이 MSE(Mean Square Error)는 좋지는 않았다. 실제 음향시스템의 모델링에는 거의 같은 MSE을 갖으며, 수렴 속도에는 모두 빠른 성능을 보였으며, 이를 음질향상에 적용하여 향상된 음질을 얻을 수 있었다.

• Journal of the korean Society of Automotive Engineers
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• v.18 no.3
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• pp.45-54
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• 1996

최근 자동차의 안전성을 한층 강조하는 ASV 개념의 도입이 보편화되면서 이를 구현하기 위한 여러가지 기능들이 고안되어 지고 있는데, 그 중에서도 추돌경보 및 회피기능, 야간보행자 검지기능, 후측방 장애물검지 기능, 차간거리 일정유지 제어기능 등에 있어서 공통적으로 주행중 거리계측이 필요하다. 본고에서는 ASV기술에서 필요하고 또한 중요한 핵심기술인 차량탑재용 거리계측기술에 대하여 현재 실용화되어 있거나 실용가능성이 있는 기술을 수단과 방식으로 나누어 각각의 원리와 특징에 대해 소개하였다. 수단으로서는 초음파, 레이저, 밀리파를 제시하였으며, 방식으로는 펄스시간차방식, 진폭변조 및 위상복조방식, 주파수변조방식을 소개하였다. 또한 비젼은 이들과는 계측원리와 신호처리가 매우 상이하고 본특집에서 별도로 상세히 소개될 것이기 때문에 간략히 소개하였다.