• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.6-11
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• 2012

A bidirectional TDM-PON link to support 2.5 Gb/s upstream signals of 256 ONUs was considered for an extended transmission distance of 50 km. The power budget of the link was 58 dB for the upstream signal and a SOA was applied as a link extender which had a 25 dB gain. Receiver sensitivity of the upstream signal was -25 dBm for -30 dBm input power to the SOA. When the input power was -10 dBm, pulse overshooting caused by gain transient of the SOA was maximum at 45% and the signal performance degradation gave a power penalty of 1.55 dB for $10^{-12}$ BER. However the penalties diminished rapidly and became negligible as the input power went below -15 dBm. So this input power dynamic range of up to -15 dBm means that it is not positively necessary to use gain control methods for the next generation TDM-PON systems.

• 전자공학회논문지 IE
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• v.47 no.2
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• pp.60-65
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• 2010

In this paper, we propose a dual-band filtering method optimized to DBO-CSS systems which are alternatively transmitted in low and high bands. The conventional channel filter which passes entire signal bandwidth causes a problem that excessive noise in neighboring sub-band is added while one of signals in two sub-bands is received. The dual-band filtering proposed in this paper can overcome the performance degradation in the conventional filtering method without increase of hardware complexity. The proposed method is based on two filters to be matched with DBO-CSS signals receiving alternatively and can exclude the undesired noise in neighboring sub-band. Simulation results for the proposed method show better performance about 2.5dB than the conventional one.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.2
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• pp.42-46
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• 2018

Adaptive signal processing is quite important in various signal and communication environments. In adaptive signal processing methods since the least mean square(LMS) algorithm is simple and robust, it is used everywhere. As the step is varied in the variable step(VS) LMS algorithm, the fast convergence speed and the small excess mean square error can be obtained. Various variable step LMS algorithms are researched for better performances. But in some of variable step LMS algorithms the computational complexity is quite large for better performances. The fixed step LMS algorithm with a low computational complexity merit and the variable step LMS algorithm with a fast convergence merit are combined in the proposed sporadic step algorithm. As the step is sporadically updated, the performances of the variable step LMS algorithm can be maintained in the low update rate using Fibonacci sequence. The performances of the proposed variable step LMS algorithm are proved in the adaptive equalizer.

• The Korean Journal of Financial Management
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• v.9 no.2
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• pp.209-242
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• 1992

본 연구에서는 무상주발행, 즉 무상증자(無償增資), 주식분할(株式分割), 그리고 주식배당(株式配當)을 실시하는 기업(企業)의 특성(特性)과 주가반응(株價反應)을 연관지어 주가반응(株價反應)의 이유를 설명하였다. 특히, 이러한 형식적 재무활동이 왜 기업내용에 관한 정보전달의 역할을 하게 되며, 장기적 기업성과의 변화로 이어지는가, 배당증감(配當增減)에 관한 직접적인 정보(情報)에 상관없이 무상주발행 발표시점에서 정보효과(情報效果)를 갖는가, 그리고 정보효과(情報效果)에 차이(差異)가 있는가를 살펴보았다. 실증분석(實證分析) 결과(結果)는 무상증자(無償增資) 및 주식분할(株式分割)은 기업의 경영성과(經營成果)가 전과 같이 탁월(卓越)하거나 또는 평균이상(平均以上)을 유지(維持)하리라는 신호(信號)를 시장에 주는 정보효과(情報效果)를 갖고 있었으며, 주식배당(株式配當)은 현금배당능력(現金配當能力)이 부족(不足)한 기업(企業)들이 실시하고 주식배당 후에도 경영성과가 저조했다. 그러나 모든 무상주 발행의 경우 배당증가의 경우가 배당감소의 경우보다 초과수익이 더 많아 정보효과(情報效果)의 차이(差異)를 발견하였고, 또한 배당증감에 관한 직접적인 정보에 상관없이 공시시점(公示時點)에서 정보효과(情報效果)를 가지고 있다는 사실도 알 수 있었다. 무상증자(無償增資)가 주식분할보다 특정기간에 더 높은 초과수익을 실현하고 있었으며, 자본잉여금(資本剩餘金)을 재원(財源)으로 한 무상증자는 이익잉여금(利益剩餘金)을 재원(財源)으로 한 경우보다 초과수익(超過收益)이 많았다. 기업특성(企業特性)에 있어서도 자본잉여금을 재원으로 한 경우가 이익잉여금의 경우보다 경영성과가 더 우수했으며 특히, 이익잉여금(利益剩餘金)의 경우 대부분이 회계년도말(會計年度末)에 실시되어 주식배당적성격(株式配當的性格)이 강하였다. 무상증자의 경우 종합주가지수수익율(綜合株價指數收益率)을 이용하여 구한 잔차가 업종별지수수익율(業種別指數收益率)을 이용하여 구한 잔차보다 크며 통계적으로 유의하였다. 이는 무상증자가 있는 업종의 수익률이 시장평균보다 높다는 것을 말하며, 무상증자(無償增資)를 실시하는 기업들은 평균보다 많은 투자기회(投資機會)를 가지고 보다 우월한 영업성과를 줄 것으로 기대되는 업종에 속하고 있다고 하겠다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.1
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• pp.27-35
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• 1998

In this paper, we propose a novel spectral-chopping model of Class-II$(1+D)^2$ -PRS system which reveals improved spectral efficiency. We build up the model having spectrum chopped by the amount of Nyquist over-rate, and then compare its characteristics with the conventional model in both the time-domain and the frequency-domain. When the transmission system operates above the Nyquist rate, the new model has better performance than the conventional PRS using its inherent speed-tolerance. According to our investigations, Class-II PRS shows more excellent effect in the spectral-chopping method than Class- I and W types analyzed previously. We ascertain that the over-rate of 26.675 obtained by the inherent speed-tolerance could be improved upto 40% using spectrum-truncation. These effects come from the fact that the raised-cosine spectrum of Class-II PRS has smaller Boss of frequency component and energy than any other types for the same amount of truncation. In order to validate these theoretical results, we present their sidelobe-trends confirming cancellation effects at the sampling instants and some experimental results showing their patterns of eye-openings and spectra.

• The Korean Journal of Financial Management
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• v.24 no.1
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• pp.1-27
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• 2007

In this study, we investigated the market long-term performance of stock splits by using the Korean Stock Market data from 1998 through 2002. We measured the performance by the event-time portfolio approach with the buy-and-hold abnormal return(BHAR) and the cumulative average abnormal return(CAAR). Also, the calendar-time portfolio approach with one-factor and three factor model were used for avoiding the misspecification model problem. The first of main results in this study was that the stock splits had significantly positive abnormal returns around the month of the stock splits announcements. However, the period BHAR and CAAR after the announcement month were significantly negative. This negative long-term abnormal returns were confirmed by the calendar-time portfolio approach. The results suggested that the abnormal return followed by the stock splits seemed to be positive in the short-term period. Second, there was no the difference of the long term performance between the high and the low split ratios. The operating income performance in the periods followed by the stock splits announcements grew worse. Therefore, the signalling effects, the managers of the firm under considering the stock splits would make use of splits as a form of signals for the upward changes in the cash flow or profits, could not be found. Finally, in contrast to Fama, Fisher, Jensen and Roll(1969), the significant negative abnormal returns following the stock splits were still found irrespective of the change of dividend payout ratio.

• Journal of Korean Society of Transportation
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• v.23 no.8 s.86
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• pp.181-191
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• 2005

This study developed an algorithm for real-time signal control based on the detection system that can collect sectional travel time. The signal control variable is maximum queue length per cycle and this variable has a sectional meaning. When a individual vehicle pass through the detector, we can gather the vehicle ID and the detected time. Therefor we can compute the travel time of an individual vehicle between consecutive detectors. This travel time informations were bisected including the delay and not. We can compute queue withdrawing time using this bisection and the max queue length is computed using the deterministic delay model. The objective function of the real-time signal control aims equalization of queue length for all direction. The distribution of the cycle is made by queue length ratios.

• Journal of Korean Society of Transportation
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• v.20 no.5
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• pp.163-174
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• 2002

Speeding has been reported as one of the major causes for fatal traffic accidents in Korea. The resolution against this dangerous speeding comes to make the automated speed enforcement system an enforcement tool. The speed detection device, which measures speeds of each incoming vehicles using double loop sensors, requires high accuracy. The object of this study is to develop an accurate speed measurement algorithm using double loop detectors. Some important findings are summarized as follows: 1) It was found that speed measurement errors are caused by scanning rate, distance of two loops, irregular vehicle trajectories, multiple vehicles in detection zone. 2) A proposed algorithm using two signal set proved to reduce variance as well as mean of speed measurement. 3) A proposed filtering algorithm was effective to filter irregular driving vehicles and multiple vehicles in detection zone. A comprehensive field test of developed algorithm resulted in significant improvement of speed measurement accuracy.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.6
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• pp.479-486
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• 2021

In this paper, an ultra small phase locked loop (PLL) with a single capacitor loop filter has been proposed by adding a signal sensing circuit (SSC). In order to extremely reduce the size of the PLL, the passive element loop filter, which occupies the largest area, is designed with a very small single capacitor (2pF). The proposed PLL is designed to operate stably by the output of the internal negative feedback loop including the SSC acting as a negative feedback to the output of the single capacitor loop filter of the external negative feedback loop. The SSC that detects the PLL output signal change reduces the excess phase shift of the PLL output frequency by adjusting the capacitance charge of the loop filter. Although the proposed structure has a capacitor that is 1/78 smaller than that of the existing structure, the jitter size differs by about 10%. The PLL is designed using a 1.8V 180nm CMOS process and the Spice simulation results show that it works stably.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.6
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• pp.706-715
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• 2012

Electro-optical sigma-delta modulators are the core module of digital receiver to digitize wideband radio-frequency signals directly at an antenna. Electro-optical sigma-delta modulators use a pulsed laser to oversample an input radio-frequency signals at two Mach-Zehnder Interferometer(MZI) and shape the quantization noise using a fiber-lattice accumulator. Decimation filtering is applied to the quantizer output to construct the input signal with high resolution. The jitter affects greatly on reconstructing the original input signal of modulator. This paper analyzes the performance of first order single bit electro-optical sigma-delta modulator in the time domain and the frequency domain. The performance of modulator is analyzed by using asynchronous spectral averaging of the reconstructed signal's spectrum in the frequency domain. The reference value of time jitter is presented by analyzing the performance of jitter effects. This kind of jitter value can be used as a reference value on the design of modulators.