• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.84-85
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• 2008

In this paper, differential cross coupled LC VCOs with two noise frequency filtering techniques are proposed. Both VCOs are based on symmetric capacitor with asymmetric inductor tank structure. The VCO using low pass filtering technique shows low phase noise of -130.40 dBc/Hz at 1 MHz offset when the center frequency is 1.619 GHz. And the other VCO using band pass filtering technique shows -127.93 dBc/Hz at 1 MHz offset frequency when center frequency is 1.604 GHz. Two noise frequency filtering techniques are approached with different target.

• ETRI Journal
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• 제31권6호
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• pp.755-764
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• 2009

This paper presents a switched self-biasing and a tail current-shaping technique to suppress the 1/f noise from a tail current source in differential cross-coupled inductance-capacitance (LC) voltage-controlled oscillators (VCOs). The proposed LC VCO has an amplitude control characteristic due to the creation of negative feedback for the oscillation waveform amplitude. It is fabricated using a 0.13 ${\mu}m$ CMOS process. The measured phase noise is -117 dBc/Hz at a 1 MHz offset from a 4.85 GHz carrier frequency, while it draws 6.5 mA from a 0.6 V supply voltage. For frequency tuning, process variation, and temperature change, the amplitude change rate of the oscillation waveform in the proposed VCO is 2.1 to 3.2 times smaller than that of an existing VCO with a fixed bias. The measured amplitude change rate of the oscillation waveform for frequency tuning from 4.55 GHz to 5.04 GHz is 131 pV/Hz.

• 한국환경보건학회지
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• 제41권5호
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• pp.358-367
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• 2015

Objectives: This study was performed to evaluate the analytical method for PAH metabolites in human urine using enzyme hydrolysis and solid-phase extraction coupled with LC-(ESI)-MS/MS technique. Methods: We employed HPLC tandem mass spectrometry techniques with appropriate pre-treatment for analysis of 16 OH-PAHs in human urine. Samples were hydrolysis by ${\beta}$-flucuronidase/Aryl sulfatase, and target compounds were extracted by solid-phase extraction with a strata-x cartridge. Cross-validation was performed between Eulji University and Green Cross laboratories with 200 human urine samples. Results: The accuracies were between 90.3% and 118.8%, and precisions (relative standard deviations) were lower than 10%. The linearity obtained was satisfying for the 16 OH-PAH compounds, with a coefficient of determination ($r^2$) higher than 0.99. The results of cross-validation at the two organizations were compared by ICC (interclass correlation coefficient) values. The cross-validation results were excellent or good for all compounds. Conclusion: An analytical method was validated for low nanogram levels of 16 OH-PAHs in human urine. Also, satisfying results were obtained for method validation such as accuracy, precision and ICC of cross-validation.

• 한국ITS학회 논문지
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• 제4권2호
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• pp.73-79
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• 2005

본 논문에서는 3가지 형태의 CMOS 직교 신호 발생 전압 제어 발진기를 설계 및 제작하여 위상 잡음 특성을 비교하였다. 첫 번째 구조는 PMOS를 이용하여 두개의 Colpitts 발진기를 구성한 후 이를 상호 결합시킨 구조이다. 두 번째와 세번째 구조는 각각 일반적인 LC VCO와 펼형 콜피츠 구조에 주파수 2분주기를 연결하여 직교신호를 얻는 구조이다. 모의실험 결과 콜피츠 구조를 사용한 구조가 LC 발진기를 사용하였을 때에 비해 위상 잡음 특성이 6 dB 이상 개선되었다.

• 한국환경농학회지
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• 제34권3호
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• pp.230-237
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• 2015

BACKGROUND: To identify the sources of inaccuracy in LC/MS/MS methods used in the routine quantitation of small molecules are described and discussed. METHODS AND RESULTS: Various UPLC coupled to triple quadrupole mass spectrometer and time of flight (TOF) were used to identify the potential sources of inaccuracy and inducing the pitfalls of qualification and quntitation during the veterinary drug residue analysis. Some of stable isotope labelled veterinary drugs, which were used as internal standards, presented "cross-talk", regardless of manufactures of mass spectrometer and types of spectrometer. Group of sulfonamides also presented inaccuracy qualification and quantitation due to the multi-residue analytical method with the same fragment ions at the close retention times. CONCLUSION: The phenomena of "cross-talk" occurring between subsequently monitored transition from stable isotope labelled and isotope non-labelled authentic chemical were identified. To prevent errors and achieve more accurate data during the analysis of small molecules by LC/MS/MS SRM method, Followings should be taken care of and kept checking; purity and concentration of stable isotope as an internal standard, prevention of carry-over during the separation in column, minimizing the ion suppression by matrix effect, identification of retention time, precursor ion and product ion, and full knowledge of data processing including smoothing and peak integration.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.413-414
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• 2008

A 2.4 GHz low phase noise fully integrated LC voltage-controlled oscillator (VCO) in $0.18\;{\mu}m$ CMOS technology is presented in this paper. The VCO is optimized based on phase noise reduction. The design of the VCO uses differential varactors which are adopted for symmetry of the circuit, and consider AM-PM conversion due to a cross-coupled pair. The VCO is designed to draw 3 mA from 1.8 V supply voltage. Simulated phase noise is -137.3 dBc/Hz at 3 MHz offset. The tuning range is found to be 300 MHz range from 2.3 GHz to 2.6 GHz.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.417-418
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• 2008

A quadrature voltage controlled oscillator(QVCO) with MOS-varactors has been fabricated for X-band applications. The QVCO consists of two cross -coupled differential cores and buffer amplifiers, which has fabricated in TSMC $0.18{\mu}m$ CMOS process. The QVCO exhibits a frequency tuning range from 8.38 GHz to 10.62 GHz. The phase noise is -88 dBc/Hz at 1 MHz-offset frequency. The total bias current is 25 mA including four buffer amplifiers.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
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• pp.145-148
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• 2002

In this paper, a voltage controlled oscillator (VCO) with automatic amplitude control is designed using a 0.35${\mu}{\textrm}{m}$ CMOS process. A cross-coupled PMOS pair is used for a negative resistance to compensate for the losses in the LC resonator, and an automatic\ulcorner amplitude control function is adapted to provide constant output power independent of the Q-factor of the LC resonator. The designed VCO operates in the 200MHz to 550MHz frequency range using different external resonators. The simulated phase noise is -128 dBc/Hz at 100KHz offset from the carrier frequency of 260MHz. It dissipates 0.㎽ from a 3V power supply. The area is 300${\mu}{\textrm}{m}$ x1201${\mu}{\textrm}{m}$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2333-2335
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• 2005

Various CMOS quadrature-voltage-controlled oscillators(QVCOs) are designed and fabricated for the comparison of the phase noise. The core VCO is composed of two Colpitts oscillators which are cross-coupled with PMOS pair. For the comparison of phase noise with the proposed scheme, the conventional LC VCO followed by the frequency-divide-by-two is designed. The simulation result demonstrate that the proposed scheme shows better phase noise performance by 6dB than that of a conventional scheme in which LC VCO is followed by the frequency-divide-by-two.

• 한국전자파학회논문지
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• 제15권2호
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• pp.145-151
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• 2004

본 논문은 5 GHz 대역의 저위상잡음 특성을 갖는 모두 집적화된 LC Tank 전압제어 발진기를 설계 제작하였다. 제작된 전압제어발진기는 PN 다이오드를 사용하여 튜닝되며, 제어 전압 0∼3 V 하에서 튜닝 범위는 5.01∼5.30 GHz의 290 MHz 튜닝 범위를 가진다. 우수한 위상 잡음 특성을 얻기 위해 LC 필터링 기법을 이용하여 전류 전원 트랜지스터의 열잡음의 상향 변환을 막았다. 측정 결과 위상잡음은 -87.8 dBc/Hz＠100 kHz offset, -111.4 dBc/Hz＠1 MHz offset의 우수한 특성을 보였다. 또한 LC 필터로 인해 약 5 dB의 위상잡음 특성이 개선됨을 알 수 있었으며, 이는 HBT 공정을 이용한 최초의 실험적 결과이다. 제작된 전압제어 발진기의 FOM은 -172.1 dBc/Hz이며, 이는 5 GHz 대역의 InGaP HBT VCO 중 최고의 성능이다. 또한 본 논문에서 제안한 발진기는 기존의 InGaP HBT를 이용한 VCO에 비해 더 낮은 DC 전력을 소모하며, 더 높고 평탄한 출력 전력 특성을 보였다.