• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1079-1086
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• 2012

In this paper, X-band 60 W Solid-State Power Amplifier with sequential control circuit and pulse width variation circuit for improve bias of SSPA module was designed. The sequential control circuit operate in regular sequence drain bias switching of GaAs FET. The distortion and efficiency of output signals due to SSPA nonlinear degradation is increased by making operate in regular sequence the drain bias wider than that of RF input signals pulse width if only input signal using pulsed width variation. The GaAs FETs are used for the 60 W SSPA module which is consists of 3-stage modules, pre-amplifier stage, driver-amplifier stage and main-power amplifier stage. The main power amplifier stage is implemented with the power combiner, as a balanced amplifier structure, to obtain the power greater than 60 W. The designed SSPA modules has 50 dB gain, pulse period 1 msec, pulse width 100 us, 10 % duty cycle and 60 watts output power in the frequency range of 9.2~9.6 GHz and it can be applied to solid-state pulse compression radar using pulse SSPA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3A
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• pp.205-210
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• 2002

In a Doppler weather radar, high resolution windspeed profile measurements are needed to provide the reliable detection of hazardous weather conditions. For this purpose, the pulse pair method is generally considered to be the most efficient estimator, However, this estimator has some bias errors due to asymmetric spectra and may yield meaningless results in the case of a multimodal return spectrum. Although the poly-pulse pair method can reduce the bias errors of skewed weather spectra, the modes of spectrum may provide more reliable information than the statistical mean for the case of a multimodal or seriously skewed spectrum. Therefore, the idea of relatively simple mode estimator for a weather radar is developed in this paper, Performance simulations show promising results in the detection of hazardous weather conditions.

• Tribology and Lubricants
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• v.20 no.3
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• pp.125-131
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• 2004

Nano-wear behavior of amorphous carbon films was studied by Atomic Force Microscopy. The a-C films are deposited on Si(100) substrate by DC magnetron sputtering method. The influences of different surface roughness on the nano-wear are investigated. Nano-wear tests were carried out using a very sharp diamond coated tip. Its spring constant was 1.6 N/m and radius of curvature was 110 nm. Normal force used in the wear tests ranged 0 to 400 nN. It was found that surface depression occurred during scratching because of plastic deformation and abrasive wear (cutting St ploughing). Wear depth increased linearly with normal force. Changing the surface roughness variables according to the bias pulse control, the less surface roughness decreased the wear depth. The thickness did not affect the wear resistance.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.210-214
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• 2007

Silicon nanoparticles are widely studied as a material with great potential for wide applications. For application to present industry, it should be easy to control the characteristics of nanoparticle including the size and structure. In this paper, we investigated the formation of Si nanoparticle using pulse plasma technology. Plasma technology is already quite common in device industry and the size of nanoparticle can be easily controlled according to plasma pulse duration. An inductively-coupled plasma chamber with RF power (13.56 MHz) was used with DC-biased grid $(-200\sim+200\;V)$ installed above the substrate. In order to measure the shape and size of nanoparticle, TEM was used. It was found that the size of nanoparticles can be controlled well with the plasma pulse duration and the collection efficiency is increased with the use of either negative or positive DC-bias.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.2
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• pp.87-97
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• 2013

Negative bias temperature instability (NBTI) and positive bias temperature instability (PBTI) are critical circuit reliability issues in highly scaled CMOS technologies. In this paper, we analyze the impacts of NBTI and PBTI on SRAM $V_{MIN}$, and present a design solution for mitigating the impact of NBTI and PBTI on SRAM $V_{MIN}$. Two different types of SRAM $V_{MIN}$ (SNM-limited $V_{MIN}$ and time-limited $V_{MIN}$) are explained. Simulation results show that SNM-limited $V_{MIN}$ is more sensitive to NBTI while time-limited $V_{MIN}$ is more prone to suffer from PBTI effect. The proposed NBTI/PBTI-aware control of wordline pulse width and woldline voltage improves cell stability, and mitigates the $V_{MIN}$ degradation induced by NBTI/PBTI.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.247-250
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• 2002

This paper proposes a PWM circuit using CMOS OTAs. The features of the proposed PWM circuit are IC oriented circuits, simple configuration, and bias current controlled output. In order to verily the validity of the proposed circuit, it is simulated by H-SPICE program. Futhermore, the proposed circuit is integrated on chip using 0.35 $\mu\textrm{m}$ CMOS technology.

• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.185-188
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• 2001

This paper proposes an error amplifier circuit using OTA(Operational Transconductance Amplifier) which is the main constituent element in pulse width modulation circuit. The proposed OTA error amplifier circuit is featured by simple circuit configuration, excellent high frequency characteristics and bias current controlled output. Through the experiment of pulse width modulation circuit, the validity of the operation of the OTA error amplifier circuit is verified.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.112-112
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• 2011

300 mm 웨이퍼용 도핑장치에서 2 MHz 유도결합 플라즈마와 8 kHz의 기판 바이폴라 펄스 바이어스에 의한 플라즈마에 대해 수치 계산이 수행되었다. 한 주기에서 0, -500, +100 V의 Pulse duration동안 기판 전체에 100, 500, 150 eV 부근의 이온 입사 에너지 분포를 보였으며, 이에 따라 기판 가장자리에서의 이온 입사 각도는 -30~+$30^{\circ}$ 사이에서 변화함으로서 도핑 불균일에 대한 원인을 확인하였다.

• Journal of Navigation and Port Research
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• v.29 no.4
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• pp.341-347
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• 2005

A unique technique to extract the phase in time domain is proposed in order to measure the time parameters such as speed and depth by transmitting sound and electric waves. In the signal analysis processing, the phase of pulse signal can be transformed and digitalized with local data in real time without the effect of direct current bias and Nyquist limits. This method is sensitive to base frequency of pulse signal with high spacial resolution and is effective to compare two signals which have different forms. It is expected that the phase analysis technique will be applied to the measurement of the speed and depth accurately by ultrasonic pulse signal in water.

• Nanomaterials
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• v.12 no.24
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• pp.4457-4467
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• 2022

SiO₂ etching characteristics were investigated in detail. Patterned SiO₂ was etched using radio-frequency capacitively coupled plasma with pulse modulation in a mixture of argon and fluorocarbon gases. Through plasma diagnostic techniques, plasma parameters (radical and electron density, self-bias voltage) were also measured. In this work, we identified an etching process window, where the etching depth is a function of the radical flux. Then, pulse-off time was varied in the two extreme cases: the lowest and the highest radical fluxes. It was observed that increasing pulse-off time resulted in an enhanced etching depth and the reduced etching depth respectively. This opposing trend was attributed to increasing neutral to ion flux ratio by extending pulse-off time within different etching regimes.