• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.7
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• pp.1249-1255
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• 2008

1530nm band has been studied as pump wavelength for long-wavelength-band erbium-doped fiber amplifier (L-band EDFA). The pump source is built using a tunable light source and cascaded conventional-band (C-band) EDFA. The L-band EDFA uses a forward pumping scheme. Within the 1530nm band, 1545nm pump demonstrates 0.45dB/mW gain coefficient, which is twice better than that of conventional 1480nm pumped EDFA. The noise figure of 1530nm pump is at worst 6.36dB, which is 0.75dB higher than that of 1480nm pumped EDFA. Such high gain coefficient indicates that the L-band EDFA consumes low power.

• The Journal of the Acoustical Society of Korea
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• v.26 no.2
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• pp.69-74
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• 2007

In signal processing applications with highly correlated input signals, subband affine projection algorithm and step size controlling is a good solution for improving the slow convergence rate and large computational complexity of LMS-type algorithms. This paper proposes a subband affine projection algorithm using a variable step size. The proposed method achieves fast convergence rate and small steady-state error with a small computational complexity by combining the SAP and step size controlling in a subband structure. Experimental results on highly correlated input signal show that the proposed method is superior to the conventional methods.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1996.10a
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• pp.725-727
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• 1996

• Proceedings of the Korean Vacuum Society Conference
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• 1993.07a
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• pp.19-19
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• 1993

• Information and Communications Magazine
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• v.19 no.12
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• pp.14-25
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• 2002

• The Journal of the Acoustical Society of Korea
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• v.23 no.6
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• pp.481-487
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• 2004

In this paper. the structure of bandwidth scalable wideband speech codec and its high-band codec are proposed. In the high-band codec. the signal is divided into frequency bands. and each band is quantized in DCT domain. The DCT coefficients are splitted into magnitude and sign, and each is quantized independently by a specialized method based on its characteristics. In addition. the quantized gain parameter in the low-band codec is utilized in the high-band codec for an enhanced performance. The bandwidth scalable wideband speech codec using G.729E for low-band and the proposed codec for high-band is developed, and it is confirmed that the proposed codec has better subjective performance than 24kbps G.722.1.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.4
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• pp.325-332
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• 2004

In this paper, we propose a new DSSS-QPSK baseband modem receiver structure. A general receiver consists of matched filter, do-spreader, and DLL(Delay Locked Loop). In this paper, the matched filter plays a role of the do-spreader using the structure similarities between the matched filter and the de-spreader. As a result of the new receiver architecture, we can reduce the computational expenses and get the simpler receiver structure. This result can be used as an important part in designing the high speed modem. And, through the computer simulation and the experiment with the proposed architecture, we show that the proposed receiver structure yields fast operation speed and simple overall architecture.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.73-76
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• 2000

본 논문에서는 음향반향제거기를 구현하기 위한 적응알고리즘을 제안한다 특히 긴 임펄스 응답을 가지는 시스템의 식별을 위해 웨이블릿 필터를 사용하여 입력신호를 서브밴드로 분해함으로써 기존의 RLS알고리즘의 계산량을 줄여 수렴속도를 향상시켰다. 이 과정에서 적응필터를 다위상 구조로 구성하여 컨벌루션 과정을 병렬처리가 가능하도록 하였다. 제안된 알고리즘의 성능분석을 위하여 실제 음성신호를 입력신호로 하여 컴퓨터 모의실험을 수행하였으며 전대역 RLS알고리즘과 비교하였다.

• Electronics and Telecommunications Trends
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• v.21 no.5 s.101
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• pp.119-128
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• 2006

밴드구조 엔지니어링과 분자선 에피택셜 성장법에 의해 실현된 양자종속레이저는 유럽, 미국을 중심으로 활발한 연구가 진행되고 있으며, 눈부신 발전을 거듭해왔다. 최근, 중적외선 영역에서의 실온 연속 레이저 발진과 테라헤르츠 영역에서 파장이 약 $100\mum$를 넘는 레이저 발진이 실현되어 큰 주목을 끌고 있다. 본 고에서는 발광층 디자인을 중심으로 양자종속레이저의 원리 및 성능에 대하여 소개한 후, 이 분야에 있어서 지금까지 이루어진 기술적인 약진에 대하여 기술한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.594-594
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• 2013

금속이 첨가된 타이타니아 물질은 밴드갭이 감소해 자외선보다 파장이 긴 가시광 영역에서도 광촉매 반응을 나타낸다. 바나듐이 도핑된 타이타니아를 sol-gel법으로 제조하여 가시광과 자외선 환경에서 methylene blue의 감소량을 측정해 촉매특성평가를 하였다. 기존 상용 타이타니아(Degussa, P25)를 대조군으로 특성을 평가한 결과 가시광 영역에서 초기 반응 속도가 3배 이상 빨라짐을 확인하였다. UV-vis를 사용해 optical band gap을 측정한 결과 밴드갭이 감소함을 확인할 수 있었다. 도핑이 끝난 타이타니아 전구체 물질을 AAO template 위에 코팅한 후 sodium hydroxide로 template을 제거 후 나노그물을 제작하였다.