• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10A
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• pp.1223-1229
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• 2004

A variable-gain low-voltage low noise amplifier MMIC operating at 5GHz frequency band is designed and implemented using the ETRI 0.5$\mu\textrm{m}$ GaAs MESFET library process. This low noise amplifier is designed to have the variable gain for adaptive antenna array combined in HIPERLAN/2. The feedback circuit of a resistor and channel resistance controlled by the gate voltage of enhancement MESFET is proposed for the variable-gain low noise amplifier consisted of cascaded two stages. The fabricated variable gain amplifier exhibits 5.5GHz center frequency, 14.7dB small signal gain, 10.6dB input return loss, 10.7dB output return loss, 14.4dB variable gain, and 2.98dB noise figure at V$\_$DD/=1.5V, V$\_$GGl/=0.4V, and V$\_$GG2/=0.5V. This low noise amplifier also shows-19.7dBm input PldB, -10dBm IIP3, 52.6dB SFDR, and 9.5mW power consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.458-465
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• 2004

To reaffirm the use of a mainstream CMOS process for designing passive-like attenuator structures, a linearly controlled variable attenuator is realized with 0.35${\mu}{\textrm}{m}$ 2-poly 4-metal CMOS process. It uses the П configuration for large attenuation range and suitable matching property. Compared to conventional passive-like CMOS attenuators, it is demonstrated that this work advances the frequency band from MHz to ㎓ (DC- l㎓), and reduces the size to 700${\mu}{\textrm}{m}$${\times}$300${\mu}{\textrm}{m}$.. Both simulation results and test results are provided. They show the improved linear relation between attenuation and control voltage. It is very useful in CDMA or GSM band, which uses under 1㎓ frequency band. An alternative topology, Bridged-T configuration, is proposed to get over the limit of applications by elevating operation bandwidth. The proposed topology covers over DC-2㎓ frequency band, which means that the proposed architecture can cover the tripleband (800MHz CDMA/GSM, 1.5㎓ GPS, 1.9㎓z PCS system) in applications as well. The simulation results are provided.

• Journal of Navigation and Port Research
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• v.30 no.10 s.116
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• pp.847-853
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• 2006

In this paper, we designed VCO(voltage controlled oscillator} that is composed of a dielectric resonator and a varactor diode, and the PLDRO(phase locked dielectric resonator oscillator) that is combined with the sampling phase detector and loop filter. The results at 12.05 GHz show the output power is 13.54 dBm frequency tuning range approximately +/- 7.5 MHz, and power variation over the tuning range less than 0.2 dB, respectively. The phase noise which effects on bits error rate in digital communication is obtained with -114.5 dBc/Hz at 100 kHz offset from carrier, and The second harmonic suppression is less than -41.49 dBc. These measured results are found to be more improved than those of VCO without adopting PLL, and the phase noise and power variation performance characteristics show the better performances than those of conventional PLL.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.2
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• pp.128-134
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• 2008

The variable speed engine generator set is interested for an isolated power system due to reduced fuel consumption and less emission. However, because of sluggish dynamic behavior of the internal combustion engine the power quality would be degraded during the sudden load power surge, where the power required by the load is not available by the engine due to the reduced engine speed. An isolated power system based on variable speed engine with a super-capacitor bank can improve dynamic characteristics under such a sudden load change, and power quality, fuel consumption, and pollutants can be improved remarkably. Also, it is verified by the computer simulation that the inverter of 3phase-4leg is compatible to the isolated power system with unbalanced load. In this paper, the feasibility of the system has been verified based on a 26kw commercial diesel engine system.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.6
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• pp.432-440
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• 2010

In this paper, a LC series resonant boost converter using a single switch is proposed. The proposed topology contains additional passive elements in the conventional boost converter and performs Zero Voltage Switching(ZVS) without an additional auxiliary switch when a main switch turned on and off. The switch off time of the proposed system determined by LC series resonance, thus a on-time variable Pulse Frequency Modulation(PFM) method is adapted to control output voltage in the proposed converter. Operational modes of the proposed topology are divided with respected to the current conduction paths and then through the theoretical analysis and experimental results, operational modes and characteristics of the proposed converter are verified.

• Journal of the Korean Vacuum Society
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• v.8 no.1
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• pp.75-82
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• 1999

Ion energy is one of the crucial property in thin film deposition by internal ICP assisted I-PVD. As ion energy is determined by the difference between the plasma potential and the substrate bias potential, ICP excitation frequency was tested with medium frequency of 4 MHz and two types of tuning circuits, alternate and floating LC network with a biasing resistor, were tested. The results showed that plasma potential was less than 5 V in a range of Ar pressures, 5mTorr to 30 mTorr, at 4 MHz RF 600 W and 60 V of maximum RF antenna voltage was maintained either at RF input or output terminal. By proper control of RLC circuit installed after after RF antenna, 50V of RF induced voltage on RF antenna was obtained at 500W input power. The total impedance of RF antenna and plasma was around 10$\Omega$, and minimum RF voltage was obtained with a condition of lowest reactance at most 0.05$\Omega$.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.262-264
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• 2007

최근 전압 및 주파수 가변을 이용하여 전동기의 속도를 제어하여 전동기 경부하시 베인에서 소모되는 에너지 절감효과를 얻을 수 있는 인버터 시스템이 널리 사용되고 있다. 이에 전력연구원은 6.6kV, 1MVA급 인버터 개발 및 동해화력 발전처에 설치, 보일러 점화 전/후 시험, 계통 병입 후 부하 시험 등을 국내 최초로 성공적으로 완료하여 현재 이차 공기 송풍기 구동용 인버터는 상업 운전 중이다. 본 논문에서는 기존 동해화력 발전 설비와 신규 인버터 시스템의 인터페이스 부분에 해당하는 보일러 DCS 로직과 계통 병입 후 시운전 결과에 대하여 상세히 기술하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.871-876
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• 2011

In this paper, a voltage-controlled frequency tunable current-mode integrator and a 3rd-order current-mode Chebyshev filter in 1.8V-$0.18{\mu}m$ CMOS is realized for software radio applications in system-on-chips. This filter is used for reconstruction purposes between a current-steering DAC and a current-mode mixer. Power consumption of the designed filter can be reduced by using a current-mode small size integrator. And also, cutoff frequency of this filter is variable between 1.2MHz and 10.1MHz, the power consumption is 2.85mW. And the voltage bias compensated circuit is used to control the voltage variation.in the designed filter.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.3 no.2
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• pp.25-30
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• 2010

In this paper, a novel notch resonator is proposed based on Rectanglar Split Ring Resonator (R-RSS) element. We represented the electrical characteristics for R-SRR elements coupled with microstrip line, and measured result is compared with electromagnetic simulation (HFSS) result. We also solved equivalent circuit for R-SRR element, and also discussed influences of change structural parameters of R-SRR. the size of R-SRR is the most important parameters for frequency tuning. Also we can make tunable resonator form the basic structure. This novel resonator can apply to design of tunable bandpass filter and voltage control oscillator.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1348-1354
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• 2015

In this paper, chaotic circuit of the voltage controlled Lorentz system for engineering applications has been designed and implemented in an electronic circuit. The proposed circuit consists of MOS variable resistor, multipliers, capacitors, fixed resistors and operational amplifiers. The circuit was analysed by PSPICE program. PSPICE simulation results show that chaotic dynamics of the circuit can be controlled by the MOS variable resistor through time series analysis, frequency analysis and phase diagrams. Also, we implemented the proposed circuit in an electronic hardware system with discrete elements. Measured results of the circuit showed controllability of the circuit using the MOS resistor.