• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2617-2624
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• 2012

Interferential currents (IFC) and transcutaneous electrical nerve stimulation (TENS) are used for pain management. This study compared the analgesic effects of IFC and TENS on experimentally induced ischemic pain in otherwise pain-free subjects using a modified version of the submaximal-effort tourniquet technique. The subjects were 14 volunteers (7 male, 7 female) without known pathology that could cause pain. Their mean age was $26.7{\pm}2.0$ years. A single-blind, sham controlled, parallel-group method was used. The primary outcome measure was the change in the self-report of pain intensity during 1 of 3 possible interventions: (1) IFC, (2) TENS, or (3) sham electrotherapy. The IFC and TENS were administered on the forearm, and the sham electrotherapy group received no current output via a dummy stimulator. The results show that a 2-way repeated-measures analysis of variance revealed that there was no change in pain intensity during treatment when all 3 groups were considered together. The mean to pain intensity with the IFC intervention was no different than with TENS. Thus, Statistical analysis showed that both interventions decreased the pain intensity ratings significantly and the difference between interventions was not simply insignificant. IFC has been shown to be more comfortable than TENS in present studies and is likely to be better accepted and tolerated by patients, clinical investigation is warranted.

• Journal of the Korean Vacuum Society
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• v.21 no.5
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• pp.264-272
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• 2012

In this paper, we report THz generation and detection characteristics investigated by InGaAs semiconductor epilayers, as results of a basic study obtained from the InGaAs-based THz transmitter/receiver (Tx/Rx). High-temperature and low-temperature (LT) grown InGaAs epilayers were prepared by the molecular beam epitaxy technique for the characterization of THz generation and detection, respectively, and the surface emission based on the photo-Dember effect was tried for THz generation. THz wave was generated by irradiation of a Ti:Sapphire fs pulse laser (60 ps/83 MHz), and a LT-GaAs Rx was used for the THz detection. The frequency band shown in the spectral amplitudes Fourier-transformed from the measured current signals was ranging in 0.5~2 THz, and the signal currents were exponentially increased with the Tx beam power. The THz detection characteristics of LT-InGaAs were investigated by using an Rx with dipole (5/20 ${\mu}m$) antenna, and the cutoff frequency was ~2 THz.

• Journal of the Korean Magnetics Society
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• v.18 no.5
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• pp.174-179
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• 2008

The measurement dissolution sensor system using GMR-SV device with magnetic sensitivity of 0.8 %/Oe and Mg-film thick of 200 nm and Mg-foil thick of 50 mm was fabricated and characterized. During the water dissolving process of Mg-film and Mg-foil, the subtle variation of magnetic field by the decrease of current in solenoid was detected by the GMR-SV sensor. The variations of Mg bubble number and ORP as a function of time for three different kinds of edible, tap, and distilled water, are measured and compared. A After 45 min, the speed of fast dissolving Mg was shown the order of edible > tap > DI water. The variation of output magnetoresistance as a function of dissolved time of Mg-film and Mg-foil for edible water, which is composed of mineral content of $0.8{\sim}5.4\;mg/l$ was investigated. The response times for the dissolution in edible water were 5 min and 20 min, respectively. From the measurement of dissolving time and speed for Mg-film and Mg-foil using GMR-SV device, the mineral Mg sensor system in edible water can be possible to develop.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.12
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• pp.75-82
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• 2010

This paper presents a wideband ${\Delta}{\Sigma}$ fractional-N frequency synthesizer for a multi-band single chip CMOS RFIC transceivers. A wideband VCO utilizes a 6-bit switched capacitor array bank for 2340~3940 MHz frequency range. VCO frequency calibration circuit is designed for optimal capacitor bank code selection before phase locking process. It finishes the calibration process in $2{\mu}s$ over the whole frequency band. The LO generation block has selectable multiple division ratios of ${\div}2$, ${\div}16$, and ${\div}32$ to generate LO I/Q signals for T-DMB/DAB/FM Radio systems in L-Band (1173~1973 MHz), VHF-III (147~246 MHz), VFH-II (74~123 MHz), respectively. The measured integrated phase noise is quite low as it is lower than 0.8 degree RMS over the whole frequency band. Total locking time of the ${\Delta}{\Sigma}$ frequency synthesizer including VCO frequency calibration time is less than $50{\mu}s$. The wideband ${\Delta}{\Sigma}$ fractional-N frequency synthesizer is fabricated in $0.13{\mu}m$ CMOS technology, and it consumes 15.8 mA from 1.2 V DC supply.

• Journal of the Korean Electrochemical Society
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• v.12 no.4
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• pp.342-348
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• 2009

Zn/Air secondary batteries are high energy density type and environment-friendly. Also, they have safer properties than batteries of other type by low manufacturing cost and using the electrolyte solution. But, they have a weak concerning large output discharge. Oxygen evolution reaction(OER) and oxgen reduction reaction(ORR) in aqueous solution make a result of a decrease of cell efficiency and life span. Therefore, to minimize the voltage drop from between OCV and charge/discharge voltage is key point. The problem should be solved through developing catalysts of high efficiency. In this study, we synthesized $Pr_{1-x}(Sr,\;Ca)_x\;CoO_3$ powders by citric method and then measured physical characteristics of each powder by XRD, SEM, TGA etc. We examined its electrochemical properties by the cathodic polarization, anodic polarization and cyclic voltammogram. We achieved results that new catalysts showed better performances than existing $La_{1-x}Sr_xCoO_3$, $La_{1-x}Ca_xCoO_3$, ect. catalysts prepared in our lab.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.70-79
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• 2003

In this paper, T5 28-watt fluorescent lamp ballast using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed electronic ballast is composed of basic circuits and blocks, such as rectifier part, active power factor corrector part, frequency oscillation part using microcontroller and feedback control, piezoelectric transformer and resonant half bridge inverters. The fabricated ballast uses to variable frequency methode in external so exciting that the frequency of piezoelectric transformer could be generated by voltage control oscillator using microcontroller(AT90S4433). The current of fluorescent lamp is detected by feedback control circuit. The signal of inverter output is received using Piezoelectric transformer, and then its output transmitted to fluorescent lamp. Traditional electromagnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight. A new electronic ballast is operated at high frequency about 75kHz, and then Input power factor, distortion of total harmonic and lamp current crest factor are measured about 0.9!35, 12H and 1.5, respectively Accordingly, the traditional ballast is by fabricated electronic ballast using piezoelectric transformer and voltage control oscillator because of its lighter weight, high efficiency, economic merit and saving energy.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.5
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• pp.87-93
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• 2010

This paper presents a high resolution, wide input range 2-step time-to-digital converter used in digital PLL. TDC is used to compare the DPLL output frequency with reference frequency and should be implemented with high resolution to improve the phase noise of DPLL. The conventional TDC consists of delay line realized inverters, whose resolution is determined by delay time of inverter and transistor size, resulting in limited resolution. In this paper, 2-step TDC with phase-interpolation and Time Amplifier is proposed to meet the high resolution and wide input range by implement the delay time less than an inverter delay. The gain of Time Amplifier is improved by using the delay time difference between two inverters. It is implemented in $0.13{\mu}m$ CMOS process and the die area is $800{\mu}m{\times}850{\mu}m$ Current consumption is 12 mA at the supply voltage of 1.2 V. The resolution and input range of the proposed TDC are 0.357 ps and 200 ps, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.5
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• pp.71-79
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• 2010

This paper presents a design of a LLC resonant controller IC. LLC resonant controller IC controls the voltage of the 2nd side by adjusting frequency the input frequency of the external resonant circuit. The clock generator is integrated to provide the pulse to the resonant circuit and its frequency is controlled by the external resistor. Also, the frequency of the VCO is adjusted by the feedback voltage. The protection circuits such as UVLO(Under Voltage Lock Out), brown out, fault detector are implemented for the reliable and stable operation. The HVG, and LVG drivers can provide the high current and voltage to the IGBT. The designed LLC resonant controller IC is fabricated with the 0.35 um 2P3M BCD process. The overall die size is $1400um{\times}1450um$, and supply voltage is 5V, 15V.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.12
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• pp.7-12
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• 2004

In this paper, CPW wideband distributed amplifier was designed and fabricated using 0.1 $\mum$ InGaAs/InAlAs/GaAs Metamorphic HEMT(High Electron Mobility Transistor). The DC characteristics of MHEMT are 442 mA/mm of drain current density, 409 mS/mm of maximum transconductance. The current gain cut-off frequency(fT) is 140 GHz and the maximum oscillation frequency(fmax) is 447 GHz. The distributed amplifier was designed using 0.1 $\mum$ MHEMT and CPW technology. We designed the structure of CPW curve, tee and cross to analyze the discontinuity characteristics of the CPW line. The MIMIC circuit patterns were optimized electromagnetic field through momentum. The designed distributed amplifier was fabricated using our MIMIC standard process. The measured results show S21 gain of above 6 dB from DC to 45 GHz. Input reflection coefficient S11 of -10 dB, and output reflection coefficient S22 of -7 dB at 45 GHz, respectively. The chip size of the fabricated CPW distributed amplifier is 2.0 mm$\times$l.2 mm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.897-903
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• 2011

This paper presents a highly linear power amplifier MMIC, having an output power level of about 1 watt, based on InGaP/GaAs hetero-junction bipolar transistor(HBT) technology for the 900 MHz band. The active bias circuit is applied to minimize the effect of temperature variation. Ballast resistors are optimized to prevent a current collapse and a thermal runaway. The fabricated power amplifier exhibited a gain of 17.6 dB, an output P1dB of 30 dBm, and a PAE of 44.9 % at an output P1dB from the one-tone excitation. It also showed a very high OIP3 of 47.3 dBm at an average output power of 20 dBm from the two-tone excitation.