• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.19-19
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• 2009

TiNxOy/TiNx multilayer thin films with a high resistance (~ k$Omega$) were deposited on SiO2/Si substrates at room temperature by sputtering. The TiNx thin films show island and smooth surface morphology in samples prepared by dc and rf magnetron sputtering, respectively. TiNxOy/TiNx multilayer has been developed to control temperature coefficient of resistance (TCR) by the incorporation of TiNx layer (positive TCR) inserted into TiNxOy layers(negative TCR). Electrical and structural properties of sputtered TiNxOy/TiNx multilayer films were investigated as a function of annealing temperature. In order to achieve a stable high resistivity, multilayer films were annealed at various temperatures in oxygen ambient. Samples annealed at 700 oC for 1 min exhibit a good TCR value and a stable high resistivity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.8 s.99
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• pp.783-789
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• 2005

In this paper, a novel design and implementation of a dual-band directional coupler based on RF IPD(Integrated Passive Device)-on-glass technology is proposed, which can be adopted in GSM/GPRS cellular phones for closed loop power control at the output of the power amplifier. The proposed coupler has a compensation capacitor to improve the directivity, and was designed using a new diplexing structure to minimize the cross-band isolation.

• Transactions on Electrical and Electronic Materials
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• v.15 no.6
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• pp.315-319
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• 2014

In this paper, we investigate visible light stress instability in radio frequency (RF) sputtered a-IGZO thin film transistors (TFTs). The oxygen flow rate differs during deposition to control the concentration of oxygen vacancies, which is confirmed via RT PL. A negative shift is observed in the threshold voltage ($V_{TH}$) under illumination with/without the gate bias, and the amount of shift in $V_{TH}$ is proportional to the concentration of oxygen vacancies. This can be explained to be consistent with the ionization oxygen vacancy model where the instability in $V_{TH}$ under illumination is caused by the increase in the channel conductivity by electrons that are photo-generated from oxygen vacancies, and it is maintained after the illumination is removed due to the negative-U center properties.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.217-218
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• 2008

Since the digital TV signal band is very wide ($54{\sim}806MHz$), the VCO used in the frequency synthesizer must also have a wide frequency tuning range. Multiple LC VCOs have been used to cover such wide frequency band. However, the chip area increases due to the increased number of integrated inductors. A general method for achieving both reduced VCO gain(Kvco) and wide frequency band is to use the switched-capacitor bank LC VCO. In this paper, a scheme is proposed to cover the full band using only one VCO. The RF VCO block designed using a 0.18um CMOS process consists of a wideband LC VCO with reduced variation of VCO gain and frequency steps. Buffers, divide-by-2 circuits and control logics the simulation results show that the designed circuit has a phase noise at 100kHz better than -106dBc/Hz throughout the signal band and consumes $9.5{\sim}13mA$ from a 1.8V supply.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.115-117
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• 2011

포항가속기연구소에서 성능향상사업으로 2.5 GeV에서 3.0 GeV로 에너지를 증강하는 사업을 추진중에 있다. 선형가속기의 전자를 가속하기 위하여 필요한 에너지 공급 장치로서 RF 증복기인 80 MW 클라이스트론과 200 MW 펄스 전원공급장치가 필요하다. 성능향상사업으로 전자를 가속하기 위하여 기존의 12set중 4set는 개조하고 4set는 추가하는 방안으로 16set의 200 MW 펄스 전원공급장치를 설치하여 운전 중에 있다. 그중 8set는 3상 AC/AC 위상제어 방식을 사용한 SCR 제어기의 출력을 승압트랜스퍼머 및 정류회로를 이용하여 고전압의 직류를 피드백 받아 일정한 펄스 전원을 공급하기 위해 설치후 시험중에 있다. 펄스를 부하로 전달시 발생하는 노이즈한 환경에서 SCR Controller의 제어방식과 설치하여 시험한 결과를 검토하고자 한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.990-992
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• 2007

The purpose of this study is to develop a practical gait-event detection system which is necessary for the FES (functional electrical stimulation) control of locomotion in paralyzed patients. The system is comprised of a sensor board and an event recognition algorithm. We focused on the practicality improvement of the system through 1) using accelerometer to get the angle of shank and dispensing with the foot-switches having limitation in indoor or barefoot usage and 2) using a rule-base instead of threshold to determine the heel-off/heel-strike events corresponding the stimulation on/off timing. The sensor signals are transmitted through RF communication and gait-events was detected using the peaks in shank angle. The system could detect two critical gait-events in all five paralyzed patients. The standard deviation of the gait events time from the peaks were smaller when 1.5Hz cutoff frequency was used in the derivation of the shank angle from the acceleration signals.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.721-724
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• 2001

In this paper, we present the effect the length the MSL(Microstrip Line) on the oscillation characteristic of the fabricated VCOs(Voltage Controlled Oscillator) designed and analyzed by RF circuit simulator Serenade(ANSOFT Co.) and fabricated by screen printing method on the alumina substrate. We have fabricated VCOs with 3 different MSL length and each MSL length of the VCO is 140mi1, 280mil and 560mi1. The oscillation frequency of each sample(VCO) was tuned to UHF band(750MHz∼900MHz) varying the capacitance. The experimental result shows the phase noise -82∼-97[dBc/Hz] at a 50 [kHz] offset frequency, the pushing figure 94∼318[kHz] at 3${\pm}$0.15[V] and the harmonics 13∼21 [dBc] between MSL length 140mi1s and 560mi1. The frequency and output variation width are 779∼898[MHz], -36∼-33[dBm] at MSL length 140mi1; 818∼836[MHz], -27.19∼-27.06[dBm] at 280mi1;751.54∼751.198[MHz],-33.44∼ -33.31[dBm] at 560mi1. we examined 3 VCOs oscillation characteristic difference through comparison with phase noise, oscillation power and frequency by control voltage change, harmonics and pushing figure for each sample.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.834-837
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• 2005

In this paper, we describe the method of non-invasive blood pressure measurement using pulse wave transit time(PWTT). PWTT is a new parameter involved with a vascular that can indicate the change of BP. PWTT is measured by continuous monitoring of ECG and pulse wave. No additional sensors or modules are required. In many cases, the change of PWTT correlates with the change of BP. We measure pulse wave using the photo plethysmograph(PPG) sensor in an earlobe and we measure ECG using the ECG monitoring device our made in the chest. The measurement device for detecting pulse wave consists of infrared LED for transmitted light illumination, pin photodiode as light detector, amplifier and filter. We composed 0.5Hz high pass, 60Hz notch and 10Hz low pass filter. ECG measurement device consists of multiplexer, amplifier, filter, micro-controller and RF module. After amplification and filtering, ECG signal and pulse wave is fed through micro-controller. We performed the initial work towards the development of ambulatory BP monitoring system using PWTT. An earlobe is suitable place to measure PPG signal without the restraint in daily work. From the results, we can know that the dependence of PWTT on BP is almost linear and it is possible to monitoring an individual BP continuously after the individual calibration.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1606-1611
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• 2005

The goal of this paper is to develop a self localization of mobile robot using UHF RFID landmark. We present landmark, a location sensing archetype system that uses UHF Radio Frequency Identification (UHF RFID) technology for locating objects inside buildings. The major advantage of landmark is that it improves the overall accuracy of locating objects by utilizing the concept of reference tags. Based on experimental analysis, we demonstrate that passive UHF RFID is a viable and cost-effective candidate for indoor location sensing. We conduct a series of experiments to evaluate performance of the positioning of the landmark System. In the standard setup, we place RF Reader which has two antennas and 25 tags in our lab. This research uses the assumption-based coordinates (ABC) algorithm[3] for determining the localization of robot. Also, we show how Radio Frequency Identification (UHF RFID) can be used in robot-assisted indoor navigation for the visually impaired. The experiments illustrate that passive UHF RFID tags can act as reliable landmark that trigger local navigation behaviors to achieve global navigation objectives.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.594-597
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• 2002

Silicon Oxynitride(SiON) thick films on p-type silicon(100) wafers have obtained by using plasma-enhanced chemical vapor deposition from SiH$_4$ , N$_2$O and N$_2$. Prism coupler measurements show that the refractive indices of SiON layers range from 1.4620 to 1.5312. A high deposition power of 180 W leads to deposition rates of up to 5.92${\mu}$m/h. The influence of the deposition condition on the chemical composition was investigated using X-ray photoelectron spectroscopy. After deposition of the SiON thick films, the films were annealed at 1050$^{\circ}C$ in a nitrogen atmosphere for 2 h to remove absorption band near 1.5${\mu}$m.