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디지털 비디오 방송 시스템에서의 파일럿을 이용한 반복적 주파수 옵셋 추정방법
이경택,서종수,Lee, Kyung-Taek,Seo, Jong-Soo 한국통신학회 2007 韓國通信學會論文誌 Vol.32 No.5A
OFDM(orthogonal frequency division multiplexing) 시스템은 시간 동기 및 주파수 옵셋 추정 오차에 따라 시스템 성능이 좌우된다. 본 논문에서는, OFDM을 기반으로 한 디지털 비디오 방송(digital video broadcasting) 시스템을 위한 향상된 정수배 주파수 옵셋 추정 방법을 제안한다. 제안된 정수배 주파수 옵셋 추정기는 기존의 ML 추정기에 다단계 추정 방법을 적용하여 개선한 방법이다. 실험 결과를 통해, 제안된 주파수 옵셋 추정 방법이 기존의 ML 추정기에 비해 적은 연산량으로 향상된 주파수 옵셋 추정 성능을 가진다. The main disadvantage of orthogonal frequency division multiplexing (OFDM) systems is its sensitivity to carrier frequency offset and timing offset. This paper proposes a simple way of improving the performance of the integer frequency offset (IFO) estimator in OFDM-based digital video broadcasting (DVB) system. By modifying the conventional maximum likelihood (ML) estimator to have multi-stage estimation strategy, IFO estimator is derived. Simulations indicate that the proposed IFO estimator works robustly with reduced computational burden when compared to ML estimator.
바이오가스를 이용한 가스엔진 발전기의 발전효율 및 질소산화물 배출 특성
이경택(Lee, Kyung-Taek),차효석(Cha, Hyo-Seok),전광민(Chun, Kwang-Min),송순호(Song, Soon-Ho) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.11
Concern for new and renewable energy is growing globally. Biogas is one of the alternative fuels and consists of methane and carbon dioxide. It is difficult to achieve efficient engine operation due to a lower heating value of biogas compared to that of natural gas. In order to improve generating efficiency, finding an optimum point of ignition timing and excess air ratio is important. From this fact, generating efficiency and pollutant emissions of 2300cc gas engine generator operated by biogas as functions of ignition timings and excess air ratios were investigated in this study. As a test result, the generating efficiency of the gas engine generator using biogas was 27.34 % in the condition of the BTDC of 16? and the excess air ratio of 1.4.
이경택(Lee, Kyung Taek) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.11
This paper analyzes the vibration characteristics of an optical pickup actuator, which has six wire-suspensions and is used in optical disc drives(ODDs). The vibration characteristics of the actuator is mathematically described by analyzing its beam configuration and motion condition confined to lateral and longitudinal directions of the beams. The accuracy of the vibration characteristics is proved by comparing mode frequencies with a finite element analysis. Finally, it is shown that mode frequencies and shapes can be modified by changing design parameters in mathematical expressions.