• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.64-68
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• 1994

This paper presents the structures, characteristics and shield factor of armoured communication cables used against power induction problems. The decision methods of grounding resistance and calculation formulas of shield factor are considered and improvement methods of domestic installation practice are presented.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.4 no.1
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• pp.15-21
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• 2005

One of the core technology in WDM-PON system is a generation and modulation technique of the optical source in Optical Network Unit (ONU). In this paper, we propose a reflective semiconductor optical amplifier (RSOA) as a modulator in WDM-PON system. Its performance is analyzed by simulation and actual experimentation. Using RSOA in WDM-PON system as a modulator, it obtains higher gain compared to the conventional SOA due to the double pass gain effect. Furthermore RSOA can provide high gain with comparatively low input power. This is very helpful when we set up the actually system because using lower input power, it can reduce the load of the driving circuit which makes very economical module structure. Therefore, when RSOA is used as a modulator, not only it gives noise suppression effect, but also provides certain amount of gain as well. In addition, comparing with conventional SOA which gives fairly large insertion loss, RSOA can provides more important merits.

• Journal of the Optical Society of Korea
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• v.4 no.1
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• pp.14-18
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• 2000

We have investigated gain flattening of EDFA systems with or without a gain equalizer for WDM long-haul transmission using a re-circulating EDFA loop. Without a gain equalizer, gain variation as small as 2.9 dB was achieved over the 10-nm band of a 100 cascaded EDFA system by the inversion principle. With a gain equalizer based on all-fiber acousto-optic tunable filters, two different config-urations of EDFAs were tested. For a single-stage EDFA scheme, the 21-nm band has shown 3.8 dB of gain variation at 17.4 ∼ 20.3 dB of OSNRs after the 100the stage of EDFAs. For a dual-stage EDFA scheme, a wider bandwidth of 34 nm has shown 3.6-dB variation after 40 cascaded EDFAs.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.277-278
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• 2015

해당 연구 시스템은 신재생에너지, 에너지저장장치를 연계하여 수용가의 전력소모기기를 효율적으로 제어할 수 있는 에너지 네트워크 고효율 시스템 기술로 수요반응 또는 사용자 설정에 따른 제어신호 생성 및 전달, 전력소모기기 사용량 분석을 통한 에너지 사용분석, ESS와 신재생에너지 투입에 대한 제어 및 분석, ESS, 신재생에너지, 에너지게이트웨이, 전력소모기기 간 분석을 통한 Load Balancing 기능을 제공하고자 한다. 현재는 연구단계로 설계 및 연계 통신은 완료상태이며, 주요 알고리즘 적용을 진행 중에 있다.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.185-188
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• 2005

This paper proposes a new peak-windowing algorithm with window-length adaptation for peak-to-average power reduction (PAPR) of orthogonal frequency division multiplexing (OFDM) systems. Conventional peak windowing algorithm has advantages, such as moderate system complexity with good spectral shape. However, adjacent peak signals within the length of window functions produce the distortion of signal amplitude since window functions might overap with each other. These undesired characteristics of conventional peak windowing algorithm result in the degradation of BER performance. The proposed algorithm outperforms the conventional one with the aid of window-length adaptation. Simulation results show the efficiency of the proposed algorithm under the environments of WiBro downlink systems.

• Journal of Advanced Navigation Technology
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• v.12 no.2
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• pp.139-145
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• 2008

There has been lots of studies on communication systems using millimeter wave recently in many countries, specially in newly assigned 57GHz ~ 64GHz ISM band. Among those studies, IEEE 802.15.3c standard proposes OFDM (Orthogonal Frequency Division Multiplexing) systems for high data rate transmission support. But OFDM method has the PAPR (peak-to-Average Power Radio) problem The PAPR problem is to decline the performance of the transmission system due to signals distorted severely when passing through nonlinear components such as ADC/DAC and power amplifiers. In order to solve the problem of P APR, this paper suggests SSC (Sine Soft Clipping) and analyzes the PAPR, CCDF, PSD, BER by applying SAW(Surface Acoustic Wave) filter and power amplifiers to IEEE 802.15.3.c OFDM WPAN systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.340-343
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• 2007

OFDM (Orthogonal Frequency Division Multiplexing) system is robust to frequency selective fading and narrowband interference in high-speed data communications. However, an OFDM signal consists of a number of independently modulated subcarriers, which can give a large PAPR (peak-to-Average Power Ratio) when added up coherently. In this paper, we propose a new PAPR reduction method using Adaptive Sine Soft Clipping (ASS Clipping) to solve the PAPR problem. The proposed method reduce the PAPR and out-of-band spectrum by cutting down high frequency components. From computer simulation results, we analyze the PSD (Power Spectral Density) and BER (Bit Error Rate) performance as well as PAPR reduction performance when the ASS Clipping method is applied to OFDM system.

• Journal of Service Research and Studies
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• v.5 no.1
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• pp.91-103
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• 2015

We examine the information transmission between the KT Spot and the KT Futures Index, the SK Telecom Spot and the SK Telecom Futures Index, based on the returns data offered by the Korea Exchange. The data includes daily return data from 1 January 2012 to 31 December 2014. Utilizing a dynamic analytical tool-the VAR model, Granger Causality test, Impulse Response Function and Variance Decomposition have been implemented. The results of the analysis are as follows. Firstly, results of Granger Causality test suggests the existence of mutual causality the KT Futures Index and the SK Telecom Futures Index precede and have explanatory power the KT Spot and the SK Telecom Spot However the results also identified a greater causality and explanatory power of the KT Spot and the SK Telecom Spot over the KT Futures Index and the SK Telecom Futures Index. Secondly, the results of impulse response function suggest that the KT Futures Index show immediate response to the KT Spot and are influenced by till time 4. From time 2, the impact gradually disappears. Also the SKT Futures Index show immediate response to the SKT Spot and are influenced by till time 4. From time 2, the impact gradually disappears. Lastly, the variance decomposition analysis shows that the changes of return of the KT Spot and SKT Spot are dependent on those of the KT Futures Index and the SK Telecom Futures Index. This implies that returns on the KT Spot and SKT Spot have a significant influence over returns on the KT Futures Index and the SK Telecom Futures Index. It contributes to the understanding of market price formation function through analysis of detached the KT Spot and the KT Futures Index, the SK Telecom Spot and the SK Telecom Futures Index.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.555-556
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• 2011

본 논문은 중, 고용량 통신용 정류기에 적합한 고효율 PFC Topology를 선정하여 특성 및 성능을 비교한다. 선정회로는 Conventional Average Current Mode PFC, Back-To-Back Bridgeless PFC, Semi-Bridgeless PFC, Interleaved PFC 이다. 통신용 1U 표준사이즈의 2kw PFC 정류기 제작 및 시험을 통해 각 Topology의 성능 차이점을 확인한다.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.400-402
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• 1994

The voltage drop in distribution path of battery-reserved DC power system can affect the total of battery, cable and electricity costs. To determine an optimum voltage drop in distribution path for minimizing the total cost, battery, cable and electricity costs are represented as a function of the voltage drop, respectively, and are summed up to the total cost. An optimum voltage drop is selected as the value giving the minimum total cost. In this paper, a design technique of optimum voltage drop in distribution path of DC power system is proposed to minimize the total of battery, cable and electricity costs. The design procedure is described and design curve for selecting optimum voltage drop is also presented as a function of distribution distance.