• Composites Research
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• v.33 no.3
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• pp.133-139
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• 2020

In this research, the vibration characteristics of composite quadcopter are analyzed, and avoidance design and analysis are performed to avoid resonance. The full platform of a commercial quadcopter with composite rotor arm is analyzed to see the vibration characteristics using FEM program. The manufactured stacking sequences of rotor arm is used for analysis, and the natural frequencies are compared with experimental results and simple analytic model results. It is also confirmed that the natural frequency of the particular mode is included within the operation range of the motor. The resonance avoidance design is carried out by selecting three variables from the existing model: stacking sequence, rotor-arm pipe length, and pipe thickness.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2397-2402
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• 2010

Dielectric resonator bandpass filters with various time-delay at 800MHz were designed and fabricated in this paper. from the results of this study. first of all, good response. characteristics were measured for all cases. The insertion loss was below 2dB and flatness for ripple was below 0.2dB, whereas return loss was over 20dB, respectively. The measured delay time of the fabricated prototype were 6ns, 12ns and 200s, respectively and the flatness characteristics did not exceeding Ins for all cases. Furthermore, 2~4ns of flatness were measured for 2-hole dielectric block and other dielectric resonator filters with various delay time by combination of each prototypes filters were also implemented.

• Journal of Astronomy and Space Sciences
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• v.18 no.2
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• pp.119-128
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• 2001

The oscillation frequency tuning range of waveguide Gunn oscillator and its stability depend sensitively on the dimensions of the resonator. Therefore the embedding impedances with the various dimensions of the resonator for Q-band (33 ∼ 50 GHz) Gunn oscillator are calculated by using HFSS (High Frequency Structure Simulator). In this paper the comparisons between theoretical results of embedding impedances as a function of frequency and that of experimental results are described. And the oscillation frequency range could be predicted by using the theoretical evaluation methods which were proposed in this paper It shows that post size has an effect on the frequency tuning characteristics of Gunn oscillator.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.625-632
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• 2010

The moduli of concrete has been determined by various testing methods. The impact resonance (IR) method has been shown to be truly a simple nondestructive testing method which produces consistent results. It is possible to determine not only the modulus but also damping ratio from the IR test. However, the values of elastic modulus and damping ratio of concrete from the test is known to be affected by various test conditions including, specimen support condition, impact steel ball size and sampling rate. In this study, the optimum IR test conditions are suggested and validated experimentally. The test results showed that the recommended test conditions yielded a variation of resonant frequency within ${\pm}0.3%$ and damping ratio ${\pm}10.0%$. In addition, the modulus from the IR test was comparable to that from a static test when the effect of strain amplitude was properly taken into account.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.769-772
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• 2002

본 논문에서는 직류 전기아크로의 전원장치로서 AC/DC 공진형 컨버터가 묘사된다. 또한 무효전력을 보상하기 위한 커패시터와 인덕터를 각각 직렬과 병렬로 연결되어 있다. 그러므로 무부하부터 단락회로까지의 범위에서 역률이 매우 높다. 이 컨버터는 직류 아크로의 전원장치로서 매우 적당하다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.188-189
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• 2003

어떤 특정한 주파수 범위 내에서 전자기파의 진행을 차단하는 광자 크리스탈은 광 집적회로에서 빛의 진행을 제어할 수 있는 잠재적인 능력을 가지고 있다. 따라서 최근 몇 년 동안 광자 크리스탈의 특성을 이용한 광 스위치, 광 집적회로, 광섬유, 광 분배기, 공진 캐비티, 도파로 등에 대한 연구가 활발히 이루어지고 있다. 본 논문에서는 광자 크리스탈의 두개의 선 디펙트로 구성된 도파로 사이의 공진 터널링 현상인 채널 드롭 구조를 이용하여, 새로운 1$\times$4 Demultiplexer의 구조를 제안하고 그 구현 가능성을 고찰하였다. (중략)

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.123-124
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• 2016

LLC 컨버터는 동작범위에 따라 특성이 바뀌는 전달함수로 인해 제어기 설계와 최적화에 어려움이 따른다. 본 논문에서는 이를 해결하기 위해 새로운 방식의 전하제어를 제안한다. 먼저, 소신호 등가모델을 분석해 공진 캐패시터 전압이 공진 전류와 같은 위상을 가진다는 것을 보인 후, 캐패시터가 resettable integrator가 될 수 있음을 밝힌다. 이를 바탕으로 디지털 구현에 적합한 전하제어를 제안한다. 그리고 실험을 바탕으로 제안한 제어의 타당성을 검증한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.11
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• pp.60-66
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• 2007

In this paper, a novel voltage-controlled oscillator (VCO) using the microstrip square open loop multiple split ring resonator (OLMSRR) is presented for reducing the phase noise property. The square-shaped multiple split ring resonator (MSRR) having the form of the microstrip square open loop is investigated to realize this property. Compared with the microstrip square open loop resonator and the microstrip square open loop split ring resonator (OLSRR) as well as the conventional microstrip line resonator, the microstrip square OLMSRR has the larger coupling coefficient value, which makes a higher Q value, and has reduced the phase noise of VCO. The VCO with 1.7V power suppIy has the phase noise of $-124.5\;{\sim}\;-122.0\;dBc/Hz$ @ 100 kHz in the tuning range, $5.746\;{\sim}\;5.84\;GHz$. The figure of merit (FOM) of this VCO is $-203.96\;{\sim}\;-201.6\;dBc/Hz$ @ 100 kHz in the same tuning range. Compared with VCO using the conventional microstrip line resonator, VCO using the microstrip square open loop resonator and VCO using microstrip square OLSRR, the phase noise property of VCO using the proposed resonator has been improved in 25.66 dB, 8.34 dB, and 4.5 dB, respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.84-89
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• 2010

In this paper, a novel voltage-controlled oscillator (VCO) using the microstrip square open loop dual split ring resonator is presented for reducing the phase noise. The square-shaped dual split ring resonator having the form of the microstrip square open loop is investigated to reduce the phase noise. Compared with the microstrip square open loop resonator and the microstrip square open loop split ring resonator as well as the conventional microstrip line resonator, the microstrip square dual split ring resonator has the larger coupling coefficient value, which makes a higher Q value, and has reduced the phase noise of VCO. The VCO with 1.7V power supply has the phase noise of -123.2~-122.0 dBc/Hz @ 100 kHz in the tuning range, 11.74~11.75 GHz. The figure of merit (FOM) of this VCO is-214.8~-221.7 dBc/Hz dBc/Hz @ 100 kHz in the same tuning range. Compared with VCO using the conventional microstrip line resonator, VCO using microstrip square open loop resonator, the phase noise of VCO using the proposed resonator has been improved in 26 dB, 10 dB, respectively.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.4
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• pp.100-108
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• 1997

A combined buck and boost push-pull quantum series resonant rectifier(PPQSRR) is newly proposed to achieve a power factor correction without start-up inrush current. Based on the developed dynamic modeling of the proposed rectifier, an inrush current elimination control technique is proposed and the usefullness of the proposed rectifier and control method are verified by computer simulation and experimental results. With the proposed control method, a high power factor and wide range of output voltage can be obtained.