• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.187-190
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• 2004

Transducer for ultrasonic linear motor with the symmetric and anti-symmetric modes was studied. The ultrasonic liner motor consists of two Lngevin type piezoelectric vibrators that cross at right angles with each other in tip. In order to excite symmetric and anti-symmetric mode, the transducer must have a 90 degree phase difference of voltage. Therefore, the tip of transducer moves on an elliptical motion. In this paper, the finite element analysis was used. The ultrasonic motor was fabricated using the simulated result and the driving characteristics were measured.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1950-1953
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• 1996

A $1\;{\times}\;4$ micro mirror array is designed and fabricated. In contrast to other micro mirrors which utilize torsional flexure hinges or cantilevers for restoring torque and supporting purpose, we have placed a substrate hinge structure under each mirror. Each micro mirror consists of address electrode, substrate hinge consisting of pin and staple, supporter post, and mirror plate. Electrical connection between mirror plate and ground electrode is established by substrate hinge. Mirror undergoes a rotational motion due to electrostatic force when voltage difference is applied between address electrode and mirror plate. Micro mirrors with two different types of staple shape and two different pin sizes are designed and fabricated. Each mirror is designed to have ${\pm}\;10^{\circ}$ of deflection angle and have $100\;{\times}\;110\;{\mu}m^2$ of size.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.10
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• pp.1061-1067
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• 2004

In this study, ferroelectric (Ba,Sr)TiO$_3$ and high temperature superconductor YBCO thin films were fabricated by PLD (Pulsed Laser Deposition) method and tuneable bandstop filters were implemented with two different IDC(Interdigital Capacitance) gap patterns, 20${\mu}{\textrm}{m}$ and 30${\mu}{\textrm}{m}$ using these two thin film layers. The resonant frequency was changed by DC bias voltage. By comparing measured results with simulation, the dielectric properties of ferroelectric thin film have been extracted. The permittivity was 820 ～ 900 at 30 K and had an acceptable error range but the loss tangent had a great difference, 0.018 in 30${\mu}{\textrm}{m}$ IDC gap pattern and 0.037 in 20 ${\mu}{\textrm}{m}$.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.333-339
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• 2000

This study was performed to investigate the performance of heat recovery device attached to exhaust gas funnel connected to combustion chamber of greenhouse heating system. The experiment heat recovery system is mainly consisted of LPG combustion chamber and two heat recovery units; unit-A is attached directly to the exhaust gas funnel, and unit-B is connected with unit-A. Heat recovery performance was evaluated by estimating total energy amount by using enthalpy difference between two measurement points together with mass flow rate of gas and/or air passing through each heat recovery unit depending on 5 different flow rates controlled by voltage meter. The results of this experimental study, such as heat exchange behavior of supply air pipes and exhaust air passages crossing the pipes, pressure drop between inlet and outlet, heat recovery performance of exchange unit, etc., will be used as fundamental data for designing optimum heat recovery device to be used for fuel saving purpose by reducing heat loss amounts mostly wasted outside of greenhouse through funnels.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.587-590
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• 2000

For high-accuracy signal processing of differential capacitance transducers, an interface circuitry based on a switched-capacitor sample/hold circuit is developed. Driven by nonoverlapping two-phase clocks, the interface produces the output voltage which is proportional to the ratio of difference-to-sum of two capacitors of a differential transducer. Performances of a prototype chip fabricated using 0.6 $\mu\textrm{m}$ n-well CMOS process were measured and compared with those simulated by HSPICE. The measured results indicate that 0.1% resolution is achievable with the proposed interface and the temperature-dependence of the interface is small enough fur practical applications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05a
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• pp.28-31
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• 2004

A Quadrature phase detector for high-speed delay-locked loop is introduced. The proposed Quadrature phase detector is composed of two nor gates and it determines if the phase difference of two input clocks is 90 degrees or not. The delay locked loop circuit including the Quadrature phase detector is fabricated in a 0.18 urn standard CMOS process and it operates at 5 ㎓ frequency. The phase error of the delay-locked loop is maximum 2 degrees and the circuits are robust with voltage, temperature variations.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.1
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• pp.61-70
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• 2016

This paper describes a new PMU(parametric measurement unit) design technique for automatic test equipment(ATE). Only one DDA(differential difference amplifier) is used to force the test signals to DUT(device under test), while conventional design uses two or more amplifiers to force test signals. Since the proposed technique does not need extra amplifiers in feedback path, the proposed PMU inherently guarantees stable operation. Moreover, to measure the response signals from DUT, proposed technique also adopted only one DDA amplifier as an IA(instrument amplifier), while conventional IA uses 3 amplifiers and several resistors. The DDA adopted two rail-to-rail differential input stages to handle full-range differential signals. Gain enhancement technique is used in folded-cascode type DDA to get open loop gain of 100 dB. Proposed PMU design enables accurate and stable operation with smaller hardware and lower power consumption. This PMU is implemented with 0.18 um CMOS process and supply voltage is 1.8 V. Input ranges for each force mode are 0.25~1.55 V at voltage force and 0.9~0.935 V at current force mode.

• Journal of the Korean Institute of Navigation
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• v.12 no.2
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• pp.33-42
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• 1988

As a basic study for enhancing the sensitivity of the follow-up system of the marine gyrocompass, the geometric characteristics of the deflection sensor were investigated and the theoretical model of it was formulated. The output signal voltage of the deflection sensor was esamined by changing the attitude of gyrosphere against follow-up container. The characteristics of the output are found to be indentical with those of the distance difference versus the relative azimuthal deflection of the gyrosphere against the follow up container. On the base of the theoretical model, some useful points for the design of the deflection sensor are suggested as following : 1. When the difference between semidiamter of gyrophere and that of the follow-up container decreases, the sensitivity of deflection sensor increases. 2. If the semidiameter difference of two spheres is constant, the sensitivity of deflection sensor is proportional to the magnitude of the semidiamter of each sphere. 3. The farther the gyrosphere is deviated from the center of follow-up container, the higher the sensitivity of deflection sensor is. 4. It is recommendable that the value of the datum deflection of the electrodes on the gyrosphere should be within the range between $4^{\circ}$ and $16^{\circ}$deviated from north-south line.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.399-402
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• 1997

It is important to find a accurate root canal length or successful endodontic therapy. By X-ray method takes a long time and difficult in a curved canal. After developed electronic apex locator has allowed to measure the root canal length with easy, in a short time also in a curved canal. But most electronic apex locators have the disadvantage which is too short reading or sometimes the measurement itself becomes impossible if there are electrolytes in the canal. To overcome this drawback, impedance ratio method has been developed. In this study, we have developed frequency dependent electronic apex locator to minimize the interference of electrolytes. And based on that also some error in clinic use, we added the other method. Difference of two signals which are used in calculation of impedance ratio was can be represent the status of root canal fluid. As a result, using impedance ratio method and auto-calibration by voltage difference method can reduce the measurement error.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.9
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• pp.56-63
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• 1997

There generally exists a large variation in the thereshold voltages of the flash EEPROM cells after they are erased by using th fowler-nordheim tunneling, thereby getting some cells to be overeased. If the overerased cells are programmed with the conventional one-step programming scheme where an 12-13V pulse with the duration of 100.mu.S is applie don the control gate for the programming, they can suffer from the significant degradation of the reliability of the gate oxide. A two-step programming schem, where an 8/12 V pulse with a duration of 50.mu.S for each voltage is applied on the control gate for the programming, has been studied to solve the problem. The experimental results hav eshown that there is little difference in the programming characteristics between those two schemes, whereas the degradation of the gate oxide due to the programming can be significantly reduced with the two-step programming scheme compared to that with the one-step programming scheme. This is possibly because the positive charge stored in the floating gate of the overerased cells is compensate dwith the electrons injected into the floating gate while the 8V pulse is applied on the control gate, which leaves the overerased cells in the normally erased state after the duration of the 8V pulse.