• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2002년도 종합학술발표회 논문집 Vol.12 No.1
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• pp.394-397
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• 2002

A design study of phase detectors for the 2.5 Gb/s CDR circuit using a standard 0.18-${\mu}{\textrm}{m}$ CMOS process has been performed. The targeted CDR is based on the phase-locked loop and thus it consists of a phase detector, a charge pump, a LPF, and a VCO. For high frequency operation of 2.5 Gb/s, phase detector and charge pump, which accurately compare phase errors to reduce clock jitter, are critical for designing a reliable CDR circuit. As a phase detector, the Hogge phase detector is selected but two transistors are added to improve the performance of the D-F/F. The charge pump was also designed to be placed indirectly input and output.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.421-424
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• 2002

The 3-D measurement using a sinusoidal grating pattern projection is very attractive because of its high measuring speed and high sensitivity. When a sinusoidal amplitude grating was projected on an object, the surface-height distribution of the object is translated into a phase distribution of the deformed grating image. The phase-acquisition algorithms are so sufficiently simple that high-resolution phase maps using a CCD camera can be generated in a short time. The PMP technique is discussed, and the analysis of the systematic errors, the calibration procedure designed to determined the optimal setting of the measurement parameters is illustrated. Results of measurements and calibrations on the measurement plane objects are described.

• Journal of Electrical Engineering and Technology
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• 제2권3호
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• pp.401-407
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• 2007

Precise absolute measurement of the errors in a potential transformer (PT) can be achieved using high voltage capacitance bridge (HVCB) and capacitive divider. The uncertainty in a PT measurement using the HVCB system was evaluated by considering the overall factors affecting during the calibration of a PT. The expanded uncertainties are found to be not more than $30{\times}10^{-6}$ for ratio and $30{\mu}rad$ for phase up to the primary voltage of $V_p=22kV$. For same PTs, the measured errors in KRISS (Korea Research Institute of Standards and Science) using our bridge are well coincide with those in NMIA (National Measurement Institute of Australia) and PTB (Physikalisch-Technische Bundesanstalt) within the corresponding uncertainties.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.193-196
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• 1992

When there exist parameter uncertainty, modelling errors and nonminimum phase zeros in control object system. the stability robustness of conventional LQG and LOG/LTR methods are not satisfactory[2, 8]. Since these methods are performed on the infinite horizon, it is very hard to establish exact design parameters and thus they have lots of problems to be applied to real systems, So in this paper we propose RHLQG/FIRF optimal controller which has robust stability against parameter uncertainty, nonminimum phase zeros and modelling errors. This method uses only the information around at present and therefore shows good performance even when we do not know exact design parameters. We here compare LQG and LQG/LTR method with RHLQG/FIRF controller and exemplify that RHLQG/FIRF controller has better robust stability performance via simulations.

• 전자공학회논문지A
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• 제33A권11호
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• pp.60-69
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• 1996

In this study, when the coherent detector has been developed and manufactured in the receiver of radar system, we have suggested and realized the 'Frequecny-Feedback correction (FFC)' that extracts its errors affecting the performance of radar, such as amplitude imbalances (k), phase imbalance ($\varphi$) between channels and offset votlages and corrects them to improve radar performances. Applying the FFC proposed, we analyzed sthe properties of the coherent detector and compared its perfomances after and before correction procdure. After the correction sequence, the amplitude imbalance was improved upt o 2dB and the phase imbalance over 9$^{\circ}$. The image rejection ratio (IRR), one of the figures of merit of radar system, was made better above 9 dB after correcting the coherent detector which possessed 23 dB before.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.585-591
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• 2003

It has been widely known that geometrical or form errors of ball bearings such as ball size error, ball waviness, inner and outer race waviness due to inherent manufacturing imperfection are one of the major sources of uncontrollable non-repeatable run-out (NRRO) vibration in HDD spindle motor. NRRO in HDD is also known to be the primary cause of limiting the storage capacity of HDD. In this paper, We performed vibration analysis for NRRO a ball bearing being used in 3.5" HDD spindle motor. To theoretically estimate NRRO considering the geometrical errors of ball bearing components, a simple three degrees of freedom model was proposed and then vibration analysis for axial and radial NRRO was conducted utilizing the measured geometric imperfection of a bearing with both the waviness magnitude and phase taken into account. Effects of bearing preload and clearance on NRRO was also investigated as an effort to predict their optimum values minimizing bearing NRRO.

• 한국분무공학회지
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• 제7권3호
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• pp.24-30
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• 2002

In the analysis of the mass distribution and SMD(Sauter Mean Diameter), planar laser imaging technique is a convenient and useful one when compared to the mechanical pattemator or PDPA (Phase Doppler Particle Analyzer). But recorded signals at cameras and intensity of laser are distorted by attenuation. Using experimental datum and assumptions, we study measurement errors due to attenuation in plannar image technique.

• 대한전자공학회논문지
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• 제25권12호
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• pp.1559-1565
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• 1988

In computed tomography, the errors asociated with interpolation in the reconstruction process degrade the reconstructed image and may cause divergence unless a large number of rays is used. A new data acquisition scheme without interpolation is developed in this paper. Samples (projection data ) are taken in phase with samples of the Cartesian grid to eliminated errors associated with interpolation process.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1707-1713
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• 2016

This paper proposes a dc error compensation algorithm using dq-synchronous coordinate transform digital phase-locked-loop in single-phase grid-connected converters. The dc errors are caused by analog to digital conversion and grid voltage during measurement. If the dc offset error is included in the phase-locked-loop system, it can cause distortion in the grid angle estimation with phase-locked-loop. Accordingly, recent study has dealt with the integral technique using the synchronous reference frame phase-locked-loop method. However, dynamic response is slow because it requires to monitor one period of grid voltage. In this paper, the dc offset error compensation algorithm of the improved response characteristic is proposed by using the synchronous reference frame phase-locked-loop. The simulation and the experimental results are presented to demonstrate the effectiveness of the proposed dc offset error compensation algorithm.

• 대한기계학회논문집A
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• 제26권12호
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• pp.2535-2540
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• 2002

ESPI is a noncontact, nondestructive and relatively fast inspection method. For these reasons ESPI is being applied as a valuable tool in the nondestructive evaluation of structural components. Phase shifting ESPI is used more effectively than the traditional ESPI because spatial resolution of small object displacements are improved and numerical phase values are obtained for all pixels in the image. Consequently the quantitative measurement of deformation is possible. ESPI fringe patterns are contaminated with high levels of speckle noise. Therefore the phase image is to be smoothed to remove the noise and obtain a better signal-to-noise ratio. In this study, smoothing is done by phase shifting convolution to avoid smoothing errors close to the 2$\pi$ phase ambiguities in the deformation phase image, and median filter is used as a smoothing filter.