• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.5
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• pp.889-895
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• 2008

In this paper a Fractional-N frequency synthesizer is designed for UHF RFID readers. It satisfies the ISO/IEC frequency band($860{\sim}960MHz$) and is also applicable to mobile RFID readers. A VCO is designed to operate at 1.8GHz band such that the LO pulling effect is minimized. The 900MHz differential I/Q LO signals are obtained by dividing the differential signal from an integrated 1.8GHz VCO. It is designed using a $0.18{\mu}m$ RF CMOS process. The measured results show that the designed circuit has a phase noise of -103dBc/Hz at 100KHz offset and consumes 9mA from a 1.8V supply. The channel switching time of $10{\mu}s$ over 5MHz transition have been achieved, and the chip size including PADs is $1.8{\times}0.99mm^2$.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.147-148
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• 2008

In this paper two kinds of techniques were compared for localization of PD(partial discharge) in power transformer and more useful method was suggested. Both of them, the time of arrival and the energy content method, were tested in 154kV single phase experimental transformer using UHF signal measurement. The former was using the difference of arrival time of recorded signals from four UHF sensors, the latter was based on the energy content in frequency spectra of signals detected at all sensors.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1655-1657
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• 2002

Ultra-wide bandwidth (UWB), narrow bandwidth (single frequency), and a combination of both technologies have been studied for the ultra-high frequency (UHF) partial discharge (PD) monitoring system as a detection scheme. We have experimentally compared those detection methods using a mock-up of 362 kV class single phase gas-insulated switchgear (GIS) and a stable PD source. A rolling-ball type PD cell that produces PDs of about 10 pC, is placed at one end of the GIS. An internal UHF PD sensor was attached several meters away from the PD source. The PD spectrum was measured up to 3 GHz. A useable bandwidth of more than 1 GHz was used to measure UWB signals from the PD. To simulate the narrow bandwidth scheme a bandwidth of 100 kHz centered at several different frequencies was used.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1915-1917
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• 2000

Laboratory experiments and on site measurements were conducted to detect partial discharges in GIS(Gas Insulated Switchgear) using the UHF(Ultra High Frequency) technique that has been applied many places in the world. Experimental results were in good agreement with calculation in locating a partial discharge source using mock-up GIS. Defect type and its location were inferred after a measurement on 345 kV GIS that showed some abnormal phenomenon. Precise examination inside the GIS coincided with the results inferred from the measurement. High reliability of UHF technique for site application was confirmed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.10
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• pp.1-6
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• 2007

Wireless Self-Powered Temperature Sensor for UHF Sensor Tags which are basic device for construction of ubiquitous sensor network is proposed. The key parameters of the target specification are resolution of $0.1\;^{\circ}C$ per output bit, below 1.5 V of operating voltage and below 5 uW of power consumption during sensing operation. Temperature sensor circuit consists of PTAT current generator, band gap reference circuit generating both reference voltage and current, Sigma-Delta Converter, and Digital Counter. Simulated maximum resolution was $0.23\;^{\circ}C/bit$ in 11-bit output. The proposed temperature sensor was fabricated by using a 0.25 m CMOS process. The chip area is $0.32\;{\times}\;0.22\;mm$ and the operating frequency is 2 MHz. Measured resolution from fabricated temperature sensor was $4\;^{\circ}C/bit$ in 8-bit output for the temperature range from $10^{\circ}C$ to $80^{\circ}C$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.805-810
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• 2011

This paper deals with the method and algorithm used to find fault locations in gas insulated transmission line. The method uses UHF sensors and digital oscilloscope to detect discharge signals emitted to the outside through insulating spacer in the event of breakdown inside GIL. UHF sensors are the external type and installed at outside of insulating spacers of GIL. And we used wavelet signal processing to analyze the discharge signals and confirm the exact fault location findings in the GIL test line. This method can overcome demerit of TDR(Time Domain Reflectometer) method having been applied to detect fault location for conventional underground transmission lines, and Ground Fault Sensors used in conventional GIS systems. TDR method requires high level of specialty and experience in analyzing the measured signals. Ground fault sensors are installed inside GIL and can be destroyed by high transient voltage. This paper's method can simplify the fault location process and minimize the damage of sensors. In addition, this method can estimate the fault location only by the time difference when discharge signals are arrived to detecting sensors at the ends of GIL sections without reasons of breakdown. To test the performance of our method, we installed sensors at the ends of test line of GIL(84m) and sensed discharge signals occurred in GIL, energized with AC voltage generator up to 700kV.

• ETRI Journal
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• v.30 no.3
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• pp.347-354
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• 2008

In this paper, the design of a low-power 512-bit synchronous EEPROM for a passive UHF RFID tag chip is presented. We apply low-power schemes, such as dual power supply voltage (VDD=1.5 V and VDDP=2.5 V), clocked inverter sensing, voltage-up converter, I/O interface, and Dickson charge pump using Schottky diode. An EEPROM is fabricated with the 0.25 ${\mu}m$ EEPROM process. Power dissipation is 32.78 ${\mu}W$ in the read cycle and 78.05 ${\mu}W$ in the write cycle. The layout size is 449.3 ${\mu}m$ ${\times}$ 480.67 ${\mu}m$.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.145-146
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• 2008

OO변전소 154 kV GIS에서 부분방전측정 수행을 하였다. GIS내부 결함유무 및 위치를 판정하기 위해 현장 정밀측정을 한 결과 GIS 내부에서 발생하는 부분방전신호가 아닌 외부노이즈임을 세가지 측정방법을 통해 판별할 수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.6-16
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• 2009

For the application to the direction finding(DF) antenna for V/UHF bands, circular active array composed of 9 dipole element has been investigate. For miniaturization of the overall size array, the element has been chosen to be of the top-hat dipole type. For the broadband operation over 20-1300MHz, some number of pin diodes have been inserted in each arms of each dipole element. By employing this type of each element dipole, the effective dipole length can be increased or decreased according as the inserted pin diodes is on or off. The active array antenna has been design to be directly connected to the balanced push full amplifier such that the amplifier may play a role as a balloon and may improve the sensitivity as a receiver as well. The active array antenna has been designed and fabricated. Some experimental results have been presented in comparison with simulated results.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1835-1837
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• 2004

The UHF electromagnetic waves excited by PD pulses propagate along the GIS busbar not only TEM mode, but also TE and TM mode. Generally the waves detected by the UHF sensors are those of high order modes and such waves can only propagate the higher than cut-off frequency. In this paper, computed cut-off frequency of 362[kV] GIS by each modes and simulated electromagnetic field of each propagation modes by FEM(Finite Element Method) program. Frequency band of each TEmn/TMmn modes were determinated by simulation results and were discussed optimal position of UHF sensor from this results.