• JSTS:Journal of Semiconductor Technology and Science
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• 제13권2호
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• pp.145-151
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• 2013

In this paper, a low power, small area cyclic time-to-digital converter in All-Digital PLL for DVB-S2 application is presented. Coarse and fine TDC stages in the two-step TDC are shared to reduce the area and the current consumption maintaining the resolution since the area of the TDC is dominant in the ADPLL. It is implemented in a 0.13 ${\mu}m$ CMOS process with a die area of 0.12 $mm^2$. The power consumption is 2.4 mW at a 1.2 V supply voltage. Furthermore, the resolution and input frequency of the TDC are 5 ps and 25 MHz, respectively.

• ETRI Journal
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• 제35권5호
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• pp.786-796
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• 2013

In this paper, we propose a hybrid time-division multiplexing and dense wavelength-division multiplexing scheme to implement a cost-effective and scalable long-reach optical access network (LR-OAN). Our main objectives are to increase fiber plant utilization, handle upstream and downstream flow through the same input/output port, extend the reach, and increase the splitting ratio. To this end, we propose the use of an arrayed waveguide grating (AWG) and an erbium-doped fiber amplifier (EDFA) in one configuration. AWG is employed to achieve the first and second objectives, while EDFA is used to achieve the third and fourth objectives. The performance of the proposed LR-OAN is verified using the Optisystem and Matlab software packages under bit error rate constraints and two different approaches (multifiber and single-fiber). Although the single-fiber approach offers a more cost-effective solution because service is provided to each zone via a common fiber, it imposes additional losses, which leads to a reduction in the length of the feeder fiber from 20 km to 10 km.

• 대한전자공학회논문지SD
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• 제46권1호
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• pp.92-97
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• 2009

저 전력 소모는 의료용 이식 장치에서 매우 중요한 요소가 된다. 본 논문에 제안된 이식형 심장 박동 조절기의 감지 단에 필요한 저 전력 4차 Gm-C 필터는 다단 증폭 단으로 구현 되었다. 매우 큰 시상수를 구현하기 위해서 전류 분할 및 플로팅-게이트 기법이 적용된 OTA가 사용되었다. 측정 결과, 필터는 50 dB의 SFDR을 가지며, $1.8{\mu}$, W의 전력이 소모되었다. 전원 전압은 1.5 V가 공급되었고, 코어는 $2.4\;mm{\times}1.3\;mm$의 실리콘 면적을 차지한다. 제안된 필터는 1-poly 4-metal $0.35-{\mu}m$ CMOS 공정에서 제작되었다.

• 한국음향학회지
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• 제8권5호
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• pp.33-50
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• 1989

본 논문에서는 비선헝 왜곡법을 사용하여 악기음을 합성하였다. 비선형 왜곡법은 기본적으로 하나의 정현파 발생기와 이에 의해 발생된 정현파에 인위적인 왜곡을 일으키는 증폭기로 구성된다. 출력파는 비선형 증폭기의 전달함수, 즉 파형 형성 항수를 변화시킴으로써 제어되는 배음을 갖는다. 파형 형성 함수는 녹음된 악기음을 분석하여 얻어진 각 부분음 크기를 바탕으로 체비세프 다항식을 이용하여 얻어진다. 합성 시스템은 IBM-PC에서 수행되는 프로그램이며, 합성 결과는 파형과 스펙트럼 분석기에 의한 스펙트럼으로 보였다. 또한 합성 결과의 검증을 위해 전문가를 대상으로 시청 테스트를 수행하여, 합성음의 만족도를 평가하였다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 추계학술대회
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• pp.86-89
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• 1995

A clinically oriented 32 channel Electroencephalogram (EEG) and evoked potential (EP) mapping system has been developed. The EEG and EP signals acquired from 32-channel electrodes are amplified by the pre-amplifier located near patient and are then tither amplified by main amplifier. An automatic artifact rejection scheme is employed using a neural network by which examination time is reduced substantially. Auditary and visual stimuli are used for the evoked potential mapping. A user-friendly graphical interface based on the Microsoft Window 3.1 is developed for the operation of the system. Statistical databases for the poop and individual comparisons are also included to support statistically based diagnosis.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권4호
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• pp.167-174
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• 2002

This study describes a fetal heart rate(FHR) estimation algorithm using phonogram. Using a phonogram amplifier, various fetal heart sounds are collected in a university hospital. The FHR estimation algorithms consists of a lowpass filter, decimation, envelop detection, pitch detection, and post-processing. The post-processing is the FHR decision procedure using all informations of fetal heart rates. Using the algorithm and other parameters of fetal heart sound, a fetal monitoring software was developed. This can display the original signals, the FFT spectra, FHR and its trajectory. Even though the fetal phonogram amplifier detects the fetal heart sounds well, the sound quality is not so good as the ultrasonography. In case of very week fetal heart sound, autocorrelation of it showed clear periodicity. But two main peaks in one period is an obstacle in pitch detection and peaks are not so vivid. The proposed FHR estimation algorithm showed very accurate and stable results. Since the developed software displays multiple parameters in real time and has convenient functions, it will be useful for the phonogram-style fetal monitoring device.

• 대한전자공학회논문지
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• 제25권11호
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• pp.1274-1281
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• 1988

전압제어 적분기에 기초를 둔 새로운 전압-제어 발진기를 개발했다. 전체 회로는 operational transconductance amplifier(OTA)와 접지된 커패시터로 실현한 전압제어 적분기와, 슈미트 트리거(Schmitt trigger)로 구성된다. 입력제어 전류는 적분기의 적분 시정수를 변화시키고, 이것에 의해 회로의 발진 주파수가 바뀐다. 제어 전압이 0V일때 회로를 12.21KHz에서 발진시킬 경우, -2V에서 2V의 제어 전압 범위에서 전압-주파수의 변환 감도는 2.473Hz/V이고, 최대 직선 오차는 0.68%이다. 저주파에서 100KHz까지의 주파수 범위에서 회로의 주파수 안정도는 약 +250ppm/$^{\circ}$C이다.

• 대한임베디드공학회논문지
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• 제8권3호
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• pp.129-136
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• 2013

In this paper, a motion control system based on 2-axis gimbal system is designed and implemented to drive a high speed and precision. The proposed system consists of the RS-422 interface, 2-axis gimbal platform, servo control unit integrated with a high speed DSP chip-set, servo amplifier unit, potentiometer sensor unit, and resolver sensor unit. The servo control unit using the high speed DSP firmware is designed to get a fast response without an overshoot with step input and a RMS error of low probability with ramp input. The servo amplifier unit using a voltage control is designed to resolve the zero-crossing distortion for precise motion. To verify the performance and stability of the implemented system, experiments are performed through a measurement of the time and frequency domain response in a laboratory environment by using a PXI(PCI eXtentions for Instrumentation).

• 한국군사과학기술학회지
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• 제11권5호
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• pp.5-11
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• 2008

Recently developed radars use the solid-state power amplifier to amplify the RF signal. The stability of RF signal directly depends on that of the electric power. So the stable and reliable electric power should be needed. When the electric power switch is tuned on for the first time in order to operate the radar system, the in-rush current is generated because of the capacitive characteristic. The excess in-rush current breaks the element. Therefore, the analysis about the in-rush current to design the electric power system is necessary. In this paper, modeling and simulation on the whole power system is carried out and the necessity of limiting the in-rush current is verified. After the analysis, the circuit to limit the in-rush current is designed and examined to verify the analysis. The circuit is good enough to limit the in-rush current.

• Journal of Communications and Networks
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• 제12권6호
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• pp.544-557
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• 2010

This paper addresses the problem of controlling the envelope's power peak of single carrier modulated signals, band limited by root-raised cosine (RRC) pulse shaping filters, in order to reduce power amplifier back-off for very small aperture terminals ground stations. Magnitude modulation (MM) is presented as a very efficient solution to the peak-to-average power ratio problem. This paper gives a detailed description of the MM concept and its recent evolutions. It starts by extending the look-up-table (LUT) based approach of the MM concept to M-ary constellations with M ${\leq}$ 16. The constellation and RRC symmetries are explored, allowing considerable reduction on LUT computation complexity and storage requirements. An effective multistage polyphase (MPMM) approach for the MM concept is then proposed. As opposed to traditional LUT-MM solutions, MM coefficients are computed in real-time by a low complexity multirate filter system. The back-off from high-power amplifier saturation is almost eliminated (reduction is greater than 95%) with just a 2-stage MPMM system even for very demanding roll-off cases (e.g., ${\alpha}$ = 0,1). Also, the MPMM is independent of modulation in use, allowing its easy application to constellations with M > 16.