• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.139-146
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• 2001

This paper presents a study on heat transfer and residual distortion analysis of laser welded EDFA(Erbium Doped Fiber Amplifier) LD(Laser Diode) Pump using the finite element method. In the production process of LD Pump in light-wave communication system, ferrule and saddle are welded by Nd-YAG laser. These parts experience thermal and mechanical effect during heating and cooling cycle with the laser welding. Thus distortion happens in the laser-welded packaging, and it makes an error in detecting the light signal translate through optical fiber in LD Pump. The amount of final displacement produced by the laser welding is predicted using the finite element method. And the optimal shape of saddle is proposed with the results of numerical analyses to minimize the displacement.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.9
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• pp.200-207
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• 2014

Arrhythmia electrocardiogram signal contains a specific unusual heartbeat with abnormal morphology. Because unusual heartbeat is useful for diagnosis and classification of various diseases, such as arrhythmia, detection of unusual heartbeat from the arrhythmic ECG signal is very important. Amplitude and kurtosis at R-peak point and RR interval are characteristics of ECG signal on R-wave. In this paper, we provide a method for detecting unusual heartbeat based on these. Through the value of the attribute deviates more from the average value if unusual heartbeat is more certainly, the proposed method detects unusual heartbeat in order using the mean and standard deviation. From 15 ECG signals of MIT-BIH arrhythmia database which has R-wave distortion, we compare the result of conventional method which uses the fixed threshold value and the result of proposed method. Throughout the experiment, the sensitivity is significantly increased to 97% from 50% using the proposed method.

• Journal of electromagnetic engineering and science
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• v.9 no.2
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• pp.71-77
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• 2009

OFDM(Orthogonal Frequency Division Multiplexing) signals sutler serious nonlinear distortion in the nonlinear HPA(High Power Amplifier) because of high PAPR(Peak Average Power Ratio). Nonlinear distortion can be improved by a pre-distorter, but this pre-distorter is insufficient when the PAPR is very high in an OPFDM system. In this paper, a DFT(Discrete Fourier Transform) transform technique is introduced for PAPR reduction. It is especially important to consider the memory effect of HPA for more precise predistortion. Therefore, in this paper, we consider two models, the TWTA(Traveling-Wave Tube Amplifier) model of Saleh without a memory effect and the HPA memory polynomial model that has a memory effect. We design a pre-distorter and an adaptive pre-distorter that uses the NLMS(Normalized Least Mean Square) algorithm for the compensation of this nonlinear distortion. Without the consideration of a memory effect, the system performance would be degraded, even if the pre-distorter is used for the compensation of the nonlinear distortion. From the simulation results, we can confirm that the proposed system shows an improvement in performance.

• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.131-135
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• 1999

The electronic structures and properties of layered perovskite $LaSrMnO_4$ and $SR^2MnO_4$ have been determined using the local-density full potential Imearized augmented plane wave method. The total energy calculations show that the antiterromagnetic state has lower energy than the ferromagnetic state in $LaSrMnO_4$. The jahn-Teller distortion of Mn-O octahedron produces the energy gap and the $3z^2-r^2$ orbital ordering, which stabilizes 2 dimensional antiferromagnetis state.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.652-654
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• 2016

This paper shows the Design and implementation of sinusoidal BLDC motor drive logic using SVPWM method with FPGA. Sinusoidal BLDC motor driver logic consists of sine-wave PWM generator, dead-time and lead angle control logic. PWM generator logic is designed using SVPWM method for increase of 15.5% linear domain than general sine-wave PWM. This logic is verified and implemented using Spartan-6 FPGA Board. Test results show that THD(Total Harmonic Distortion) of motor-driving current is 19.2% and rotor position resolution is 1.6 degree.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2391-2401
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• 1998

An L-band (1435-MHz~1535MHz) omnidirectional circular polarized wave antenna is designed and evaluated for transmitting/receiving of vehicle data. Conventioanl linear polarized wave antenna can not receive clearly all of the vehicle data which come from the wide driving test range on account of distortion. To vercome this problem, an omnidirectional circular polarized wave antenna is reuaried an designed. For the design, first of all, the charcteristics, design principle and theoretical background of circular polarized wav ewith a little signal loss ahve been reviewed. The characteristics of th edesigned antenna are analyzed wave with a little signal loss have been reviewed. The characteristics of the designed antenna is increased over 5dB comparing to that of linear polarized wave. Our results also demonstrate that the strength of vehicle data is flat enough over the full test range using this new antenna.

• The KIPS Transactions:PartA
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• v.13A no.5 s.102
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• pp.429-434
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• 2006

A CCTV system reduces some number of cameras if we use convex-mirror. In this case, convex-mirror Image distorted, we need transformation to flat images. In the center of mirror images, a transformed image has no distortion, but at near boundary image has plentiful distortion. This distortion is caused by occlusion of angled ray and diffraction. We know that the linear filtering approach cannot separate noise from signal where their Fourier spectra overlap. But using a non-linear discretization method, we shall reduce blurred noise. In this paper, we introduce the backward solution of nonlinear wave equation for reducing blurred noise and biased expansion of equilibrium contour. We propose, after applying the introduced method, and calculate with discretization method. To analysis the experimental result, we investigate to PSNR and get about 4dB better than current method.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1058-1060
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• 2001

The purpose of this paper is to analyze the harmonics of power electronics equipment, especially 3 phase square-wave inverter. In this paper, we simulated 3 phase square-wave inverter by using the matlab and analyzed the simulated output waveforms to analyze the harmonics included in the inverter. In the matlab we expressed to amplitude and phase of harmonics current, and calculated to total harmonics distortion of out voltage.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.11
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• pp.1819-1828
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• 1989

In this paper, we determined the modulation index for minimization of speed ripple and position error using maximum speed ripple (SRF) and maximum position error(PEF) in current source TPWM inverter. Through computer simulation, we compared with total current harmonic distortion, SRF and PEF for square wave modulation method and TPWM method. As a result, it turns out that square wave modulation method is superior to TPWM method of 3 pulses per half cycle in speed ripple and position error contents. And TPWM is better than square wave method when pulse number is more than 5. Also, in these pulse numbers, moduladtion index of minimum speed ripple and munimum position error is 0.91.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.6
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• pp.478-485
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• 2012

In this paper, a new PWM method is proposed to reduce the input current harmonics of 3 phase PWM rectifier. In the conventional carrier comparison PWM method, a triangular wave is generally used as the carrier wave. However, the large d-axis current ripple by the triangle carrier wave may be a source of large input current THD(Total Harmonic Distortion). In this paper, a new carrier comparison PWM method with saw tooth wave is proposed. Depending on the sector where the voltage command vector places, one of the rising or falling saw tooth wave is selected. To reduce the switching losses of the saw tooth carrier PWM, the discontinuous PWM is also presented. The proposed PWM method can reduce the d-axis current ripple as well as the switching losses. The performance of the conventional and proposed PWM methods is verified by the simulation and experimental results.