• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.11
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• pp.954-962
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• 1998

Energy-trapped thickness vibrations of piezoelectric substrates are utilized in fabricating resonators and filters which have their operating frequencies in HF band. Normalized particle displacement distributions of the fundamental thickness shear vibration mode and overtone modes into the thickness direction in energy-trapped resonators and double-coupled filters were obtained by solving the wave equation and calculating the solved equations. These results show that as the number order of the harmonic mode in a energy-trapped resonator becomes larger, the degree of energy-trapping in the resonator increase, and if the conditions for energy-trapping become sufficiently weak, the energy-trapping effect of the harmonic mode which has the lower order disappears the earlier. Above simulation results were proved by the experiments.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.146-148
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• 2009

본 논문에서는 매트릭스 컨버터의 입력 필터 설계를 하고, 시뮬레이션하여 타당성을 검증하고 분석한다. 매트릭스 컨버터는 18개의 양방향 스위치로 구성되어 있으며, 출력 전압을 합성하기 위해 각각의 스위치가 빠르게 온-오프 한다. 이러한 스위칭 과정에서 고차 고조파가 발생하고, 이 고조파는 매트릭스 컨버터 주위에 연결된 각종 기기에 영향을 미친다. 따라서 고차 고조파를 줄이기 위해 계통과 매트릭스 컨버터 사이에 입력 필터를 설치하여 이러한 영향을 줄여야 한다. 입력 필터의 L과 C, 그리고 공진 주파수 근처의 값을 줄이기 위한 댐핑 저항 값을 계산하는 방법을 소개하고, 타당성을 검증한다.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2274-2276
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• 2001

본 논문에서는 미세 구조물 가공 기술(MEMS)로 제작된 실리콘 자이로스코프를 위한 폐루프 제어기를 주파수 가중 $H_{\infty}$ 제어 기법과 주파수 가중 모델 축소 기법을 이용하여 설계하였다. 실리콘 자이로스코프는 수 kHz 대의 공진 특성을 이용하여 각속도를 측정하는 센서로서, 공진 주파수 영역의 특성이 매우 중요하므로 주파수 영역을 고려하고 공정 오차를 감안한 주파수 가중 $H_{\infty}$ 제어기가 필요하다. 본 논문에서는 고차 강인 제어기의 회로적 구현과 ASIC화가 가능하도록 하기 위해, 주파수 가중 모델 축소 기법을 이용하여 공진 주파수 영역에서 성능을 유지하는 저차 제어기를 설계하였으며, 시뮬레이션을 통해 기존의 제어기 및 고차 제어기와 성능을 비교하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.6
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• pp.847-854
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• 1999

In this paper, we have analysed frequency-dispersion characteristics of higher-order modes for uniform planar transmission lines, using the 2-dimensional finite-difference time-domain method. The method presented in this paper uses both informations of amplitude and phase of the electromagnetic spectrum to determine resonant frequencies, while methods previously reported use the magnitude only. This algorithm is very useful when a resonant mode has a relatively small magnitude, where the identification of the resonant mode is quite difficult. Numerical results show that a strip line supports few higher-order modes within the frequency range of 20 GHz, but there occur many higher-order modes in the structure of grounded coplanar waveguide, where resonant frequencies of the first higher-order mode is very close to those of the fundamental mode and there occur lots of very adjacent higher-order modes. As in this example, for the analysis of planar transmission lines which support many resonant modes very close each other, the method presented in this paper can be applied very efficiently.

• Journal of the KSME
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• v.27 no.6
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• pp.478-488
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• 1987

회전기계의 고성능, 고속화에 따라 베어링 유막특성에서 자려진동이 발생하기 쉬운 조건이 되고 더욱이 고압화에 의해 자동유체로부터 불안정한 힘이 증대하게 되었다. 또한, 고속화에 의해 계의 운전속도가 1차 위험속도 이상으로 되어 시동, 정지시에 위험속도를 통과하여야 하며, 고차 위험속도에서의 공진가능성 등을 충분히 검토하여야 한다. 따라서 종래의 실제방법만으로는 회전기계의 진동문제에 충분히 대처할 수 없는 상태이다.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.146-151
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• 1999

We demonstrated a harmonic mode locking scheme that used regeneratie phase modulation to get a high and stable repetition rate in a figure-of-eight fiber soliton laser. From the detected beat spectra of the laser output, a sinusoidal clock freguency tone of 400 MHz, the 96th harmonics of the fundamental mode locking frequency, was extracted with a high Q filter and was used to drive the phase modulator, resulting in stable output of soliton pulse train synchronized with the modulation signal. Generated soliton pulses had FWHM pulsewidth of 930 fs and 3.1 nm linewidth, yielding pulsewidth-bandwidth product of 0.359 that was close to the transform limit. As the modulation frequency always followed the beat frequency of laser modes, stable harmonic mode locking was achieved without the adjustment of the cavity length, which has been commonly required in actively mode-locked lasers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.4
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• pp.616-623
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• 2002

The fractal expanded antenna with the configuration of a triangular microstrip patch antenna is presented and analyzed. In the fundamental and higher mode of TFA(Triangular Fractal Antenna), resonant frequencies are controlled by changing the scaling factor. It is observed that increasing scaling factor makes the resonant frequency be spread, and decreasing scaling factor makes it be concentrated. The scaling factor is varied as the expansion and concentration of resonant frequencies. The resonant frequency in each fractal patch element is observed log -periodically. The TFA can be applied to the multiband system.

• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1288-1296
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• 2009

This paper is for multi-frequency thin film loop antenna used on smart phone, PMP and PDA like as a multi-media devices. We developed a loop pattern folding methods to reduce a thin film antenna dimension using that mutual coupling folding loop occurs the higher frequency resonation. To reduce the thin film size for loop antenna, we fold the loop pattern repeatedly control the coupling coefficient than generate a not only higher mode resonation but also basic resonation from loop pattern. To realization the thin film folded loop antenna, we used a $30mm{\times}9mm$ PI film the thickness is 20um so that we realize the CDMA850, GPS, DCS, PCS, WCDMA antenna simultaneously and it's radiation efficiency is over 50% and gain is 0dBi.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.116-125
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• 1995

Higher order nonlinear transfer functions are applied to model the nonlinear responses obtained Inn dynamic analysis of single degree of freedom systems (SDOF) subjected to wave and current loadings. The structural systems are subjected to single harmonic, two wave combination and irregular wave loading. Three different sources of nonlinearities are examined for each of the wave loading condition and it is shown that the nonlinear response appear at the resonance frequencies of the SDOF even when virtually no wave energy exists at those resonance frequencies. Higher order nonlinear transfer functions based on Volterra series representation are used to model the nonlinear responses mainly f3r the flexible systems and clearly shows the degrees of nonlinearity either as quadratic or cubic.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.5
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• pp.97-102
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• 2012

In this paper, each electrical length and harmonics of the multi-stage SIR are calculated by using the input impedance for the variable application of SIR in the microwave systems. The size reduced ratio of the SIR is slightly reduced as increasing of the number of stage. The impedance ratio between lower and higher impedance of the SIR has the dominant effect on the size reduced ratio and harmonic characteristics. Also the equivalent impedance of the SIR is a geometric mean between lower and higher impedance and the quality factor of the SIR is similar to the half-wavelength resonator's.