• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.465-470
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• 2010

The charge pump in a phase-locked loop is a key block in determining reference spurs of the VCO output signal. To reduce reference spurs, the current mismatch in the charge pump must be minimized. This paper presents a dual compensation method to reduce the current mismatch. The proposed charge pump and PLL were realized in a $0.18{\mu}m$ CMOS process. Measured current matching characteristics were achieved with less than 1.4% difference and with the current variation of 3.8% in the pump current over the charge pump output voltage range of 0.35-1.35V at 1.8V. The reference spur of the PLL based on the proposed charge pump was measured to be -71dBc.

• Korean Journal of Optics and Photonics
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• v.11 no.3
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• pp.187-192
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• 2000

We analyze the parametric amplification by the nonlinear characteristics in a semiconductor laser using a perturbation theory and discuss its result. The parametric gain increases with increase of the pump modulation current. It is due to shift of the resonance frequency as the pump modulation current increases. However, it decreases with increase of the bias current and damping constant. Also, it needs phase matching between the pump modulation current and signal modulation current to maximize the parametric gain. The gain decreases for a large signal modulation current due to the saturation of the amplified power. power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12C
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• pp.1147-1153
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• 2009

We propose a novel image segmentation and segment-based stereo matching technique using color, depth, and motion information. Proposed technique firstly splits reference images into foreground region or background region using depth information from depth camera. Then each region is segmented into small segments with color information. Moreover, extracted segments in current frame are tracked in the next frame in order to maintain depth consistency between frames. The initial depth from the depth camera is also used to set the depth search range for stereo matching. Proposed segment-based stereo matching technique was compared with conventional one without foreground and background separation and other conventional one without motion tracking of segments. Simulation results showed that the improvement of segment extraction and depth estimation consistencies by proposed technique compared to conventional ones especially at the static background region.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.1-7
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• 2007

Generally, an electric railroad feeding system has many problems due to the different characteristics in contrast with a load of general three-phase AC electric power system. One of them is harmonics problem caused by the switching device existing in the feeding system, and moreover, the time-varying dynamic loads of rail way is inherently another cause to increase this harmonics problem. In Korea power systems, the electric railroad feeding system is directly supplied from the substation of KEPCO. Therefore, if voltages fluctuation or unbalanced voltages are created by the voltage and current distortion or voltage drop during operation, it affects directly the source of supply. The trainloads of electric railway system have non-periodic but iterative harmonic characteristics as operating condition, because the electric characteristic of the electric railroad feeding system is changed by physical conditions of the each trainload. According to the traditional study, the estimation of harmonics has been performed by deterministic way using the steady state data at the specific time. This method is easy to analyze harmonics, but it has limits in some cases which needs an assessment of dynamic load and reliability. Therefore, this paper proposes the probabilistic estimation method, moments matching method(MW) in order to overcome the drawback of deterministic method. In this paper, distributions for each harmonics are convolved to obtain the moments and cumulants of TDD(Total Demand Distortion), and this can be generalized for any number of trains. For the case study, the electric railway system of LAT(Intra Airport Transit) in Incheon International Airport is modeled using PSCAD/EMTDC dynamic simulator. The raw data of harmonics for the moments matching method is acquired from simulation of the LAT model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.1
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• pp.1-7
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• 2019

In this paper, a design technique using a bypass capacitor is proposed to improve the antenna efficiency of an inverted-F antenna (IFA) with a band stop matching circuit (BSMC). The proposed antenna operates in the LTE bands 26 and 5(814~ 894 MHz). The bandwidth of the IFA is expanded from 803~863 MHz to 800~888 MHz using the impedance change caused by the BSMC. To enhance the antenna efficiency in the expanded frequency band, the bypass capacitor is applied to the IFA with the BSMC. The bypass capacitor improves the efficiency of the antenna by reducing the current variation of the IFA with the BSMC. The proposed antenna has a bandwidth of 804~895 MHz and the antenna efficiency increases by more than 10 % in the extended frequency band by using the bypass capacitor.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1610-1613
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• 2016

An analytical method for harmonic estimation of magnetization currents has been developed. The method is based on the results of the waveforms qualitative analysis. The calculation and the experimental results are compared. A good matching is observed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8C
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• pp.1125-1132
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• 2004

In this Paper, we Propose an effective boundary matching based error detection algorithm using causal neighbor blocks to improve video quality degraded from channel error in block-coded video. The proposed algorithm first calculates boundary mismatch powers between a current block and each of its causal neighbor blocks. It then decides that a current block should be normal if all the mismatch powers are less than an adaptive threshold, which is adaptively determined using the statistics of the two adjacent blocks. In some experiments under the environment of 16bi1s burst error at bit error rates (BERs) of 10$^{-3}$ -10$^{-4}$ , it is shown that the proposed algorithm yields the improvements of maximum 20% in error detection rate and of maximum 3.5㏈ in PSNR of concealed kames, compared with Zeng's error detection algorithm.

• Journal of Korea Multimedia Society
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• v.4 no.5
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• pp.406-413
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• 2001

Ordinary high-speed block matching algorithms have a disadvantage that they need to get MAD (Mean Absolute Distance) as many as the number of search points due to comparing the MAD between the current frame's search block and the reference frame's search block. To solve such disadvantage of high-speed block matching algorithm, the proposed high-speed DS algorithm employs a MMAD calculation method using a specific characteristic that neighboring pixels have almost same values. In this thesis, we can get rid of unnecessary MAD calculation between the search point block by the new calculation method which uses the previously calculated MAD as the current search point and by breaking from the established MAD calculation method which calculates the MAD of a new search point by each search stage. Comparing with the established high-speed block matching algorithm, this new calculation's estimated movement error was shown as similar, and th total calculation amount decreased by $2FN^2Ep$.

• Korean Journal of Social Welfare
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• v.66 no.3
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• pp.133-158
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• 2014

Over the past decades, changes in economic, social and demographic structures have pushed the growth of care employment across countries around the world. Women's increasing labor force participation has squeezed the time so far available for unpaid caregiving and led to increased demand for paid care services. Population aging and increasing needs for pre-school education also have contributed to the growth in demand for care services. As a result, care workers now comprise a large and growing segment of the labor force in many countries including South Korea. But, there are not a few problems. Especially, we take underpaid and undervalued care work very seriously. care work has been generally characterized as underpaid and undervalued compared with other work in developed and developing countries alike. This study tries to show current situation of care work and estimate the wage penalty for doing care work in Korea using official employment micro-data and applying propensity matching analysis. Especially, recent expansion of social service is a big step up for Korean Welfare State. But, there are not a few problems. Especially, we take underpaid and undervalued care work very seriously. This presentation tries to show current situation of care work and estimate the wage penalty for doing care work in Korea using official employment micro-data and applying propensity matching analysis.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.9
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• pp.62-66
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• 2016

This paper presents a MedRadio-band low power low noise amplifier for Medical Devices. A proposed MedRadio-band low power low noise amplifier adopts a current-reuse resistive feedback topology to increase overall gm and reduce power consumption. The gain of the LNA increases by the Q-factor of the additional series RLC input matching network, and its noise figure is minimized by the similar factor. Furthermore, it consumes low power because of low supply voltage and current reuse technique. By exploiting the $g_m$-booting and matching network property, the proposed MedRadio-band low noise amplifier achieves a noise figure of 0.85 dB, a voltage gain of 30 dB, and IIP3 of -7.9 dBm while consuming 0.18 mA from a 1 V supply voltage in $0.13{\mu}m$ CMOS technology.