• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.191-192
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• 2007

This paper presents a 900MHz fractional-N frequency synthesizer for radio frequency identification (RFID) reader using $0.18{\mu}m$ standard CMOS process. The IC meets the EPC Class-1 Generation-2 and ISO-18000 Type-C standards. To minimize VCO pulling, the 900MHz VCO is generated by a 1.8GHz VCO followed by a frequency divider. The settling time of the synthesizer is less than $20{\mu}m$. The frequency synthesizer achieves the phase noise of -105.6dBc/Hz at 200kHz offset. The frequency synthesizer occupies an area of $1.8{\times}0.99mm^2$, and dissipates 8mA from a low supply voltage of 1.8V.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.2
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• pp.124-132
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• 1987

In this paper, a new Open and Closed Loop Alternation(OCLA) frequency synthesizer is developed to eliminate a frequency error occurring in the transition state of a frequency hopping. This frequency synthesizer consists of a phase comparator(PC), two low pass filters(LPF), two voltage controlled oscillators(VCO), switching elements, a programmable divider and frequency hopping controller, and the stabilized output frequency can be obtained by switching performance. In addigion, it can be found that the characteristic of its circuit construction makes it easy to attach an external circuitry to the open loop.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.968-971
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• 1993

Fuzzy inference system which inferences and processes the Fuzzy information is designed using digital voltage mode neural circuits. The digital fuzzification circuit is designed to MIN,MAX circuit using CMOS neural comparator. A new defuzzification method which uses the center of area of the resultant fuzzy set as a defuzzified output is suggested. The method of the center of area(C. O. A) search for a crisp value which is correspond to a half of the area enclosed with inferenced membership function. The center of area defuzzification circuit is proposed. It is a simple circuit without divider and multiflier. The proposed circuits are verified by implementing with conventional digital chips.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.456-459
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• 2004

Generally, instrument transformer of the core type have been used for measuring current. Because instrument transformer has defects, electronic instrument was appeared. Electronic instrument has many merit-linearity, small size, low cost, etc. Rogowski coil is typical electronic CT and R-divider is typical electronic VT. This paper is introduced a basic concept and theory of electronic current transformer, electronic voltage transformer.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2262-2264
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• 2005

지금까지 변전소나 개폐소에서 전류, 전압을 계측하는 수단으로서 주로 철심과 권선으로 구성되어진 변류기(CT), 계기용 변압기(PT, PD)가 사용되어져 왔다. 최근, 2차측의 계측기나 보호 Relay의 Digital화가 진전되어 또한 이것을 Digital Network으로 총합한 Intelligent 변전소의 구축이 검토되어지고 있으며, Digital Network에 대응한 변성기 관련규격인 IEC 60044가 근래 제정되어짐에 따라 이에 적합한 전자식 변성기가 요구되어지고 있다. 상기와 같은 요구로 인해 당사에서는 IEC 60044를 기반으로 한 전자식변성기 Layout을 구성하였으며, CT는 검출부에 Rogowski Coil을 적용하며 그 후단에 적분기를 설치하였으며, VD는 검출부에 중간 전극을 이용해서 분압하는 방식인 Capacitive Voltage Divider를 사용하고 증폭기를 삽입하여, 각각 요구되는 전압 신호를 얻었다. 이러한 신형 CT/VD의 적용으로 종래의 CT/PT가 차지하는 공간이 필요없게 되어 컴팩트한 GIS의 구조가 가능하게 되어 있다.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1711-1712
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• 2007

액체탱크의 레벨을 정밀측정하는 데 FMCW(Frequency Modulated Continuous Wave)를 이용하고자 한다. 우리는 1GHz 대역폭으로 Sweep하는 Frequency Source Module을 개발하여 테스트 중이다. 개발한 송수신 모듈은 주파수의 송수신을 위한 주요부품들로 구성되는데, VCO(Voltage Controlled Oscillator), 서큘레이터(Circulator), 필터(Filter), 전력분배기(Power Divider), PLL(Phase Locked Loop)제어부, 믹서, 증폭기 등이 그것이다. 이들 부품들이 위치한 RF Board와, 패치로 구성한 안테나를 이용하여 마이크로웨이브 신호를 송수신할 수 있으며, 송수신한 신호 간의 차주파수(beat frequency)성분을 측정하면 거리정보를 획득할 수 있다. 차주파수의 아날로그신호는 DSP를 이용하여 FFT를 수행하여 주파수 성분을 찾아 거리계산을 하도록 개발하였다. 거리 측정의 성능에 영향을 미치는 가장 큰 요소는 안정된 주파수를 만들어 낼 수 있느냐 하는 것이다. 본 논문에서는 제작한 VCO 모듈을 비롯한 개발 중인 각 모듈들을 소개하였다. 향후 VCO의 선형성 개선과, 난반사에 대한 Echo Cancel 알고리듬을 적용하여 제품의 상용화를 목표로 한다.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.661-662
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• 2007

We have carried out the construction of the 154kV intelligent substation with KEPRI. The intelligent substation is built in Gochang testing facility of KEPCO and consists of electronic instruments for GIS(gas insulated switchgear), digital control panel, remote monitoring and diagnosis system, and digital relay system. Rogowski coil type CT(RCT) and capacitive voltage divider(CVD) are introduced compared with the instrument transformer of conventional type. Digital control panel(DCP) replaces the LCP(local control panel) which is drived for mechanical operation. For the monitoring of the condition of GIS and TR, various sensors are used. In this paper, we mention the synopsis and report the progress state of project.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.22-24
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• 2002

지금까지 변전소나 개폐소에서 전류, 전압을 계측하는 수단으로서 주로 철심과 권선으로 구성되어진 변류기(CT), 계기용 변압기(PT, PD)가 사용되어져 왔다. 최근, 2차측의 계측기나 보호 Relay의 Digital화가 진전되어, 또한 이것을 Digital Network으로 총합한 Intelligent 변전소의 구축이 검토되어짐에 따라, Digital Network에 대응한 신형 CT, VD가 요구되어지고 있다. 상기와 같은 요구로 인해 당사에서는 CT는 검출부에 Rogowski Coil을 적용하며 그 후단에 적분기를 설치하였으며, VD는 검출부에 중간 전극을 이용해서 분압하는 방식인 Capacitive Voltage Divider를 사용하고 증폭기를 삽입하여, 각각 요구되는 전압 신호를 얻었다. 이러한 신형 CT/VD의 적용으로 종래의 CT/PT가 차지하는 공간이 필요 없게 되어 컴팩트한 GIS의 구조가 가능하게 되어 있다.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.890-893
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• 2003

In this paper, we have designed the fractional-N frequency synthesizer for bluetooth system using 0.35-um CMOS technology and 3.3-V single power supply. The designed synthesizer consist of phase-frequency detector (PFD), charge pump, loop filter, voltage controlled oscillator (VCO), frequency divider, and sigma-delta modulator. A dead zone free PFD is used and a modified charge pump having active cascode transistors is used. A Multi-modulus prescaler having CML D flip-flop is used and VCO having a tuning range from 746 MHz to 2.632 GHz at 3.3 V power supply is used. Total power dissipation is 32 mW and phase noise is -118 dBc/Hz at 1 MHz offset.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.152-156
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• 1989

Parameters of a microstrip patch antenna such as the resonant frequency, radiation conductance, and the bandwidth are calculated. The rectangular microstrip patch antenna fed by a microstrip transmission line is fabricated and its resonant frequency, radiation pattern, and input voltage standing wave ratio are measured. The measured resonant frequency for 13.0mm$\times$9.7mm copper clad woven PTFE/glass laminate plate is 9.06Ghz, where the calculative is 9.00Ghz. And the measured vswr shows that the bandwidth of the antenna is 225MHz for vswr less then 2.0 which the calculated quality factor of the patch gives the bandwidth OF 280ghZ. The measured radiation pattern for 5 element as well as 4 element patch array shows less then 4dB deviation in the first side lobes from the designed values for both E and H plane pattern. This diviation is believed to be the power division errors of the power divider.