• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1558-1559
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• 2006

펨토세컨드 원적외선 가속장치(Femtosecond Far-infrared Accelerator)에는 5 밴드의 클라이스트론이 사용되고 있으며, 이를 구동시키기 위하여 신뢰성이 높고 컴펙트하며 효율성이 좋은 펄스 모듈레이터가 필요하다. 전통적인 방식의 라인타입 공진충전 펄스 모듈레이터는 직류전원을 만들기 위하여 많은 고전압 소자들을 사용한다. 이러한 소자들로는 SCRs, 3상 트렌스포머, 정류 다이오드, 필터 초크, 필터 커패시터, 충전 인덕터, 충전 다이오드, deQing 회로, de-spiking 초크 둥으로 구성된다. 펨토세컨드 원적외선 가속장치의 펄스 모듈레이터에는 이러한 소자들을 사용하는 대신에 고전압 인버터전원장치를 사용함으로써 신뢰성이 높고 컴펙트하며 효율성이 좋은 펄스 모듈레이터를 제작하였다. 전통적인 방식의 라인타입 공진충전 펄스 모듈레이터는 deQing 회로를 사용해야만 하지만, 펨토세컨드 원적외선 가속장치의 펄스 모듈레이터의 빔 전압의 변동폭은 deQing 회로를 사용하지 않고도 0.5 % 범위안에서 동작하기 때문에 출력이 매우 안정적이다. 고전압 인버터전원장치의 사양은 10 KJ, 50KV, 200mA의 전원장치 4개를 병렬로 사용하여 30 Hz로 운전하고 있다. 본 논문에서는 펨토세컨드 원적외선 가속장치의 펄스 모듈레이터의 디자인개념과 출력전압의 변동폭에 관하여 논의하고자한다.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.175-183
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• 1999

Recently, problems related to vibrations of decomposed granite soils have acquired increasing attention in Korea because those soils cover approximately one third of the country. Both resonant column and cyclic triaxial test were performed to investigate deformation characteristics of unsaturated and cement-mixed decomposed granite soils in Suwon region. The important soil parameters in this respect are the shear moduli, dynamic moduli of elasticity and damping ratios. The dynamic parameters are influenced by variables such as strain amplitude, ratio of loading cycles, and degree of saturations, etc. Test results and data have shown that the optimum degree of saturation to the maximum shear modulus due to a capillary menisci effect was about 17~18 % at low strain amplitude and 10~15 % at intermediate strain amplitude. This paper suggests the range of threshold strain and mean shear modulus of decomposed granite soils in Suwon region. It also proposed the empirical relationship between the dynamic parameters for cement-mixed and non-mixed decomposed granite soils.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.786-795
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• 2011

This paper described the characteristic of vibration in wind turbine system including gearbox housing, gear drive, blade, generator. Especially, in planetary gear set, planet gears are supported by flexible pin. So, in planet gear, to consider not only torsional movement but also lateral movement. And include housing movement, because wind turbine system is supported by mount. To find out the characteristic of vibration, take the excitation source and study campbell diagram in operating range. Results of campbell diagram, resonances are occurred at 81.2HZ, 104.7Hz by 2nd tooth passing frequency. And resonance are also occurred at 264.5HZ, 377Hz, 424.6Hz by 3th tooth passing frequency. From the result, take vibration reduced measures.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.739-745
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• 2006

This paper presents a method to control group delay tine using a resonance circuit. The group delay time adjuster(GDTA) that can control signal group delay time comprises a variable capacitance and a variable equivalent inductor. These are coupled in parallel at a node and also controlled by two bias voltages separately, A variable equivalent inductor is realized a transmission line terminated a variable capacitor. Group delay time can be controlled by change of capacitance and inductance, but the resonating frequency is fixed. When the proposed GDTA is fabricated on RFID Korean frequency band$(908.5{\sim}914 MHz)$, a group delay variation is obtained about 3 ns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.8
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• pp.684-692
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• 2016

In this paper, a non-offset longitudinal shunt slot excited by an asymmetry compound iris on the broad wall of a rectangular waveguide is presented as an element for a waveguide slot-array antenna(WSAA). By properly adjusting the iris dimension, a resonance of the slot at a desired frequency can be achieved. The proposed resonant slot has some advantageous properties, such as a wide range of normalized resonant conductance, and minimum change of phase in the waveguide at the resonance. In addition, when the slots are arrayed for a waveguide slot antenna, the unwanted cross-polarization level can be reduced because each slot is placed in a straight line. A $8{\times}1$ WSAA with -20 dB side-lobe level(SLL) is designed, fabricated, and tested experimentally. The measured results are well agreed with the simulated ones and have an SLL of -18.13 dB and a cross-polarization level of -48.85 dB at 9.41 GHz, which was improved by about 15 dB of that of the conventional longitudinal slot array antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.813-819
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• 2011

In this paper, a new design method of a tunable oscillator using a suspended-stripline resonator is presented. The negative resistance of an FET mounted on microstrip line(MSL) is combined with a high Q suspended-stripline(SSL) resonator to produce a tunable oscillator with good phase noise. The new MSL-SSL transition facilitates the easy connection between the MSL-based circuits and the SSL module. The proposed oscillator is also frequency-tunable using a tuner located on the top of the SSL housing. The measured phase noise of the implemented oscillator at 3.37 GHz is -108.03 dBc@100 kHz and -135.09 dBc@1 MHz with 50 MHz of frequency tuning.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.398-402
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• 2003

In this paper, a VCDRO(Voltage Control Dielectric Resonator Oscillator) applied to FMCW(Frequency Modulated Continuous Wave)Radar as stable source is implemented and constructed with a MESFET for low noise, a dielectric resonator of high frequency selectivity, and high Q varator diode to obtain a good phase noise performance and stable sweep characteristics. The designed circuits is simulated thrash harmonic balance simulation technique to provide the optimum performance. The measured result of a fabricated VCDRO shows that output is 2.22dBm at 12.05GHz, harmonic suppression -30dBc, phase noise -130dBc at 100kHz offset, and sweep range of varator diode $\pm$18.7MHz, respectively. This oscillator will be available to FMCW Radar.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.386-393
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• 2000

This paper presents an improved ZVS partial series resonant DC/DC converter (PSRC) with low conduction losses, suitable for high power and high frequency applications. The proposed PSRC have advantages of zero-voltage-switching (ZVS) of main switches for entire load ranges low conduction losses of main switches by decreasing current stresses. Also the reduction of the effective duty cycle is not occurred during the resonant period of the main circuit because the auxiliary circuit of the proposed converter is placed out of the main power path. The auxiliary circuit is composed with passive components, which are an inductor, two capacitors, two diodes, and a saturable inductor. An improved ZVS PSRC has so much characteristics with respect to the overall system efficiency and to the reduction of current stresses. The operation principles of the proposed converter are explained in detail and the various simulated and experimental results show the validity of the proposed converter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.214-217
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• 2004

In this paper, a Ka-band LTCC (low temperature co-fired ceramic) narrow bandpass filter (BPF) is firstly presented. This BPF shows very narrow 3dB fractional bandwidth of 4.5 ％ centered at 28.7㎓. The advantages of multi-layered LTCC technology such as high integration and vertical stacking capabilities were employed to design three-dimensional interdigital end-coupled embedded microstrip narrow BPF. The difficulties in controlling the precise distance between two adjacent resonators in LTCC end-coupled BPF were overcome by locating the resonators on different layers. The measured insertion loss is 3dB at 28.7㎓, pass band is from 27.9 ㎓ to 29.2 ㎓, and the return loss in the pass band is less than 10 dB.

• Korean Journal of Optics and Photonics
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• v.17 no.6
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• pp.544-547
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• 2006

A time-domain modeling approach is used to study characteristics of a widely tunable coupled-ring reflector (CRR) laser diode(LD). The CRR consists of a bus waveguide and two coupled ring resonators coupled to the bus without resorting to distributed Bragg grating structure. The tuning range can be a few tens of nanometers with a side mode suppression ratio exceeding 35dB through the adjustment of currents into the phase control sections in the rings. The CRR laser diode has long effective cavity length compared to conventional laser diodes. Accordingly, a broad additional resonance peak in the amplitude modulation characteristics is observed between 20 to 30 GHz, implying the extension of amplitude modulation bandwidth.