• Journal of the Korean Graphic Arts Communication Society
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• v.15 no.2
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• pp.57-76
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• 1997

A color halftoning is the process of generating halftone images for the different color plans, for example, cyan, magenta, yellow, and black for a offset printing device. A conventional halftone technique, so called AM screening, is simple and easy to implement, but the halftoned dot patterns by using this method is not free for the moire` fringe. Moire` patterns are caused the power spectrum distribution on low spatial frequency domain. To avoid Moire` patterns, the conventional screen require the different screen angles for each color plans. Recently, Ultra-fine and 7 color printing methods are developed to expend the color gamut. In 7 color printing method must be used the halftone technique of random and blue noise characteristic to avoid Moire` fringe.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.233-236
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• 2005

Phase noise in a phase-locked-loop (PLL) is unwanted and unavoidable. It is a main concern in oscillation system especially PLL. The phase noise is derived in term of power spectrum density by using a reliable phase noise model. There are four noise sources being considered in this paper, which are generated by reference oscillator, voltage controlled oscillator, filter, and main divider. The major concern for this paper is the noise from the filter. Two types of second order low pass filter are used in the PLL system. Applying the mathematical phase noise model, the output noises are compared. The total noise from the passive filter is lower than the active filter at the offset frequency range between 1 Hz to 33 kHz.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.10
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• pp.1215-1221
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• 1999

A high speed digital distance relaying algorithm based on a Wavelet Transformation is proposed. To obtain stable phasor values very quickly, first, a lowpass filter which has low cutoff frequency is used. Secondly, db2(Daubechies 2) Wavelet which has the data window of 4 samples is used. A FIR filter which removes the DC-offset component in current relaying signals is applied. In accordance with a series of tests, the operation time of the relaying algorithm is less than 3/4 cycles after faults in a 80 [km], 154[kV], 60[Hz] over-head transmission line system.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.21-24
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• 2002

This paper presents a fully integrated, wide tuning range differential CMOS voltage-controlled oscillator, tuned by pMOS-varactors. VCO utilizing a novel tuning scheme is reported. Both coarse digital tuning and fine analog tuning are achieved using pMOS-varactors. The VCO were implemented in a 0.18-fm standard CMOS process. The VCO tuned from 1.8㎓ to 2.55㎓ through 2-bit digital and analog input. At 1.8V power supply voltage and a total power dissipation of 8mW, the VCO features a phase noise of -126㏈c/㎐ at 3㎒ frequency offset.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.618-627
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• 2005

In this paper, we have compared and analyzed the performance of high amplifier using Doherty technique to improve linearity and efficiency of base station and repeater Power amplifier for WCDMA. This Doherty amplifier implements with 3dB branch line coupler and $90^{\circ}C$ transmission line The phase offset line is designed to maintain the high linearity and efficiency at the low efficiency Period of the power amplifier CW 1-tone experimental results at the WCDMA frequency $2.11{\sim}2.17GHz$ shows that Doherty amplifier which achieves power add efficiency(PAE) of 50% at 6dB back off the point from maximum output power 52.3 dBm, obtains higher efficiency of 13.3% than class AB Finding optimum bias Point after adjusted gate voltage, Doherty amplifier shows that $IMD_3$ improves 4dB.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1937-1938
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• 2008

본 논문에서는 868/915MHz 대역 IEEE 802.15.4b LR-WPAN(Low-Rate Wireless Personal Area Network; ZigBee)시스템의 수신기를 위한 주파수 옵셋 영향을 감소시키는 알고리즘을 제안한다. 저가 구현을 지향하는 LR-WPAN 시스템의 특성에 맞추어 반송파 중심주파수의 $\pm$80ppm에 해당하는 주파수 옵셋 환경에서 안정된 수신을 보장할 수 있는 알고리즘으로 868/915MHz수신기 Correlator에 multiple delay differential filter를 적용함으로써 주파수 옵셋에 대한 강인성 및 수신 성능의 안정성을 증대시켰다.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.447-454
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• 1998

This paper describes a modeling and current control techniques of Distribution static condenser (D-STATCON) for power factor compensation. The current control is based on the predictive and the space vector PWM scheme. The predictive current controlled PWM D-STATCON can maintain its performance with power factor compensation and fixed switching frequency. By using the space vector control low ripple and offset in the current and the voltage as well as fast dynamic responses are achieved with a small DC link capacitance employed.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.3
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• pp.349-355
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• 2015

A fully-differential touch-screen sensing architecture is presented to improve noise immunity and also support most multi-touch events minimizing the number of amplifiers and their silicon area. A correlated double sampling function is incorporated to reduce DC offset and low-frequency noises, and a stabilizer circuit is also embedded to minimize inherent transient fluctuations. A prototype of the proposed readout circuit was fabricated in a $0.18{\mu}m$ CMOS process and its differential operation in response to various touch events was experimentally verified. With a 3.3 V supply, the current dissipation was 3.4 mA at normal operation and $140{\mu}A$ in standby mode.

• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.694-697
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• 2016

Up-converted phase noise, which is induced by the low-frequency relative intensity noise (RIN) of a laser through AM-PM conversion within a photodetector (PD), is first measured here by means of a cross-correlation method. Our proposed measurement system can isolate the RIN-induced phase noise from noise contributions of other components, such as amplifiers, modulators, and mixers. In particular, shot noise and thermal noise generated from the PD are also suppressed by this method, so that standalone characteristics of the RIN-induced phase noise can be obtained. Experimental results clearly show the quantitative relationship between the RIN-induced phase noise and the incident optical power of the PD. Our findings indicate that the least RIN-induced phase noise appeared at the saturation point of the PD, which is about -162 dBc/Hz at 10 kHz offset.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.109-112
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• 2007

Definition-Enhancement of the digitalized image has been being made researches continuously due to application a camera to a mobile-apparatus and the advent of a digital camera. In particular, the inputted image from a sensor goes through the process of ISP(Image Signal Process) prior to output as a visual image. The high-frequency components are offset by LPF(Low Pass Filter) that eliminates the noise of high spatial-frequency at the moment. In this paper, we propose an algorithm that outputs more vivid image by using adaptive-HPF(High Pass Filter) that has apt coefficients for diverse conditions of an image edge, nevertheless we do not employ any Edge-Detection algorithm to enhance a blurred image.