• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.437-438
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• 2009

• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.235-249
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• 2006

In this paper, SER(Symbol Error Rate) variation and effects on SER by phase noise at various frequency offset of the local oscillator in digital communication systems are gerneralyzed for QPSK(Quadrature Phase Shift Keying), MQAM(M-ary Quadrature Amplitude Modulation), OFDM(Orthogonal Frequency Division Multiplex)-MQAM, OFDM-QPSK and 8-VSB(Vestigal Side Bands) modulation methods and compared those with the ideal cases, which have no phase noise, through the MATLAB simulation. And the ration between modulation bandwidths and the SER on the various frequency offsets on the above modulation methods have been analyzed for the system requirement of minimum phase noise characteristics. From this study, we have confirmed that the most sensitive modulation method on the phase noise is OFDM-MQAM and that the relatively insensitive method 8-VSB.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.1022-1028
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• 2005

This paper is presented the analysis results and simulation results of cascaded H-bridge 7 level inverter with various modulation index. Stepped waveform having number of switching was used to eliminate harmonic components. Switching angles according to modulation index are calculated numerically. Therefore, 3 times of switching with 7 level topology and QWS(Quarter Wave Symmetry) could eliminate 5th and 7th harmonics. The harmonic characteristics are compared to those of space vector modulation method which known as common modulation method in industrial field. Stepped waveform method showed higher ability to reduce, especially lower order of harmonics.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.406-406
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• 2012

반도체 공정의 대부분은 plasma를 사용한 공정이 주를 이루고 있다. 이러한 공정에서 최근 선폭의 초 미세화가 진행되면서 pulse modulation plasma에 대한 관심을 가지게 되고 있다. Pulse modulation plasma는 RF 인가 시 일정 간격으로 on, off 시켜주게 된다. 이 때, chamber 내부에서 발생하는 plasma역시 on, off 되게 되는데 이러한 현상을 이용하면 plasma 내의 전자온도가 떨어져서 식각 공정 시 선택비의 개선을 기대할 수 있다. 실제 장비회사에서는 pulse를 이용하기 위한 장비개선 연구가 한창이다. 본 연구에서는 유도결합플라즈마 chamber에서 source와 bias에 RF pulse modulation plasma를 발생시켜 기존 CW (Continuous wave) 방전시킨 plasma의 밀도와 전자온도를 측정하여 차이를 비교, 분석 해보았다.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.175-183
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• 2003

We obtain a solution of optical parametric amplification using self-phase modulation within the Kerr media in a nonlinear interferometer with two arms. We show that it is equivalent to the solution driven by four-wave mixing and that the solution of parametric amplification is suitable to generate a parametric gain. We obtain a derivative of power gain with respect to the propagation distance and show that gain-saturation can occur as the beam propagates along the nonlinear arms. We also show a bandwidth characteristic of the parametric amplification driven by nondegenerate four-wave mixing. Numerical examples are given to illustrate that the solution of the parametric amplification can be applied to design and analysis of all-optical devices such as all-optical amplifiers.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.5
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• pp.362-369
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• 1989

A method to increase the output voltage of the PWM inverter within linear range is considered. A new modulation wave is used, which is made by injecting the third harmonic wave into the sinusoidal wave. The optimum region for improving the output voltage keeping the linear control characteristic is obtained by digital simulation. Furthermore, the distortion factor in the optimum region is less than that calculated when the maximum output voltage can be obtained in the sinusoidal PWM inverter.

• Journal of Power Electronics
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• v.5 no.4
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• pp.257-263
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• 2005

This paper describes the development and testing results of a high density High Voltage Power Supply (HVPS) that drives microwave Traveling Wave Tubes (TWTs) of phased array transmitters for airborne EW systems. The HVPS is designed to consist of a number of modules connected in series. Among them, especially, the high-density pulse transformer module including the resonant circuit is newly designed to make the HVPS much more reliable. In addition, this paper describes the development of high voltage solid-state modulation using fast switching devices (FETs) and also represents the test results of a modulator module.

• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.943-949
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• 2009

In this paper, the 5.9GHz WAVE(Wireless Access in Vehicular Environments) channel modeling is used by the Jakes channel model for the suitability of the fast wireless channel fluctuation. The performance analysed the fading signal constellation and the spectrum in the IEEE 802.11p spectrum mask, the Doppler effect, the modulation scheme. In addition, the vehicular speed, exactly the performance analysis the WAVE communication systems follow the Doppler effect.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.127-135
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• 2006

We implement numerical simulations for the distributed optical fiber sensor system that uses the spatially-selective Brillouin scattering, by treating the superposition of the optical-frequency-modulated pump/probe waves in the time domain. We obtain temporal and spatial distributions of Brillouin gain for various cases. Simulations are applied to the case of concatenated optical fibers of different kinds and the case of distributed temperature along the fiber, which give reasonable results for the distributed sensor. The result of using a triangular wave instead of a sinusoidal one as a modulation waveform shows that the triangular wave modulation has an advantage in spatial resolution.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.182-185
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• 2003

Error performance of two modulation schemes of millimeter-wave over fiber (MMoF) system i.e., optical double side band (ODSB) and optical single side band (OSSB) modulations is analyzed under Rician fading. Bit error rates (BER) of two detection techniques i.e., coherent and noncoherent detection are also compared in Rician fading. In aspect of error performance, ODSB modulation scheme has better BER than OSSB modulation scheme has under Rician fading. On the other hand, OSSB modulation scheme is advantageous in case of considering high bandwidth efficiency and small power degradation. Coherent detection technique is proper in Rician fading, because coherent detection provides more SNR gain whether fading is serious or not. Noncoherent detection can be applied when we need a simple receiver structure.