• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8A
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• pp.688-696
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• 2005

An antenna was designed and manufactured for the DBS receiver system. This antenna is a planar or flat antenna which shows many advantages over the conventional parabolic antenna such as higher aperture efficiency, easier installation and improved aesthetics to name a few. The antenna is a novel design employing microstrip annular ring resonating antenna elements and a radial waveguide feeder network. The LNB(Low Noise Blockdown Converter) is can integrate with the antenna iしt the back of the radial waveguide. The 35cm diameter antenna works at 31.8dBi minimum gain which implies an aperture efficiency of around $80\%$.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.1
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• pp.60-65
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• 2004

Induction heating system is time varying system around curie point. So, it has many troubles which are system shut down and change the load impedance. In this paper has been designed the parallel resonant inverter which controlling the constant power and tracking the load resonant frequency with PLL is possible, in order to minimize switching losses and solve it's many troubles. The current full-bridge type parallel resonant inverter of an induction heating system was composed of IGBT in switching device. For regulating the output power of an induction heating system, the Fuzzy logic controller is used. The Fuzzy controller makes the control signal for a stable power regulating control and when reference is changed, it is superior to adaptability. It has been evaluated a stable behavior for a noise with switching and a load disturbance.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.54-58
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• 2017

A combustion instability has been one of the most serious problems in the development of combustion devices including rocket engine and gas turbine. In particular, a high-frequency combustion instability generated by resonant coupling between combustion phenomena and acoustic oscillations within thrust chamber causes severe damage to the hardware. Because it is accompanied by high amplitude pressure oscillations and excessive heat flux to the chamber wall. Therefore, combustion instability is one of the difficult problems that must be resolved in developing liquid rocket engine. This paper describes the cases of combustion instability encounted during the development of thrust chamber for KSR-III and KSLV-II.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.4
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• pp.60-67
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• 2008

This paper presents a new full-bridge soft switching PWM DC-DC converter circuit topology that adding two switcher, two lossless snubber quasi-resonance capacity, two diode to power source for general welding machine. This half bridge soft switching Is low voltage hight current output that first coil current is smaller than second coil current in high frequency transformer can be obtained with decreasing path loss in conventional DC bus line switcher. As it operate ZCS/ZVS in full range, high frequency, high efficiency and high output are implemented at low voltage and high DC current switching power supplies. All of this items are got from simulation and the result of experiment. If make up for the weak points of this proposed circuit, it will be used more easily for next generation TIG, MIG and MAG type of arc-welding machine.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.26-33
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• 2008

This paper presents a new full-bridge soft switching PWM DC-DC converter circuit topology that adding one switcher, one lossless snubber quasi-resonance capacity to power source for general welding machine This full-bridge soft switching DC-DC convoter· topology can applicable 600[V] switching device (IGBT)incase of AC 400[V] common power source because the voltage of active switcher is 1/2 of DC bus line voltage. And low voltage hight current out)ut that first coil current is smaller than second coil current in high frequency transformer can be obtained with decreasing path loss in conventional DC bus line switcher. As it operate ZCS/ZVS in full range, high frequency, high efficiency and high output are implemented at low voltage and high DC current switching power supplies. All of this items are got from simulation and the result of experiment. If make up for the weak points of this proposed circuit, it will be used more easily for next generation TIG, MIG and MAG type of arc-welding machine.

• Journal of the Korea Computer Industry Society
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• v.2 no.8
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• pp.1055-1062
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• 2001

Study, it is the purpose to develope a cheap and compact pulsed $CO_2$ laser with pulse repetition rate range of 1 KHz. We used a IGBT switched power supply as a power supply, which is cheap and simple comparing to others. PIC one-chip microprocessor was used for precise control of a laser power supply on the control part. And the laser cavity was fabricated as an axial and water cooled type. The laser performance characteristics as various parameters, such as pulse repetition rate, gas pressure, and gas mixture rate have been investigated. The experiment was done under the condition of total pressure of $CO_2$： $N_2$：He ＝ 1：3：10, 1：1.5：5, 1：9：15 from 6 Torr to 15 Torr and pulse repetition rate from 100 Hz to 900 Hz. As a result, the maximum average outpu was about 20.5 W at the total pressure of 15 Torr, the gas mixture $CO_2$：$N_2$：He ＝ 1：9：15 and the pulse repetition rate of 700 Hz.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.29-35
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• 2018

In this paper, we proposed a high sensitivity sensor that can detect the concentration change of Nacl aqueous solutions by using a slot coupling capacitor resonator in sub-microwave band. The resonator applied to the sensor consists of a parallel plate capacitor connected to an inductive slot utilizing the ground plane of the microstrip line. Based on the measurement data of the dielectric characteristics according to the concentration change, the resonance frequency was determined in the UHF band where the concentration change is evident and the Nacl aqueous solution is inserted into the capacitor. Based on the simulation, the proposed resonator was designed and fabricated. The concentration level was varied from 0 to 400 mg/dl as 100 mg/dl step, and the transmission scattering coefficient ($S_{21}$) was successfully measured. Experimental results show that it is applicable to the concentration detection sensor in Nacl aqueous solution by obtaining minimum 1.8 dB($S_{21}$) at each step.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.2
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• pp.16-23
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• 2006

This paper presents a novel single-stage high frequency resonant inverter link type DC-DC converter using zero voltage switching with high power-factor. The proposed topology is integrated half-bridge boost rectifier as power factor corrector(PFC) and half-bridge high frequency resonant converter into a single-stage. The input stage of the half-bridge boost rectifier works in discontinuous conduction mode(DCM) with constant duty cycle and variable switching frequency. So that a boost converter makes the line current follow naturally the sinusoidal line voltage waveform. Simulation results have demonstrated the feasibility of the proposed high frequency resonant converter. Characteristics values based on characteristics analysis through circuit analysis is given as basis data in design procedure. Also, experimental results are presented to verify theoretical discussion. This proposed inverter will be able to be practically used as a power supply in various fields as induction heating applications, fluorescent lamp and DC-DC converter etc.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.9
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• pp.817-824
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• 2012

Transmission of unwanted vibration to sensitive systems can cause various problems including performance degradation and system malfunction. The most common approach to limit the transmission of harmful vibration disturbances to the sensitive system is adapting passive vibration isolator. The classical passive vibration isolator comprising a viscous damper and spring element in parallel, however, exhibits conflicting performance characteristics in that low amplification at the resonance, which is desirable, can only be achieved at the sacrifice of vibration isolation performance in high frequency region, which is undesirable. In this paper, vibration isolation characteristics of various passive isolator schemes in literature to circumvent this conflict are introduced and compared.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.232-237
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• 2012

Transmission of unwanted vibration to sensitive systems can cause various problems including performance degradation and system malfunction. The most common approach to limit the transmission of harmful vibration disturbances to the sensitive system is adapting passive vibration isolator. The classical passive vibration isolator comprising a viscous damper and spring element in parallel, however, exhibits conflicting performance characteristics in that low amplification at the resonance, which is desirable, can only be achieved at the sacrifice of vibration isolation performance in high frequency region, which is undesirable. In this paper, vibration isolation characteristics of various passive isolator schemes in literature to circumvent this conflict are introduced and compared.