• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.5
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• pp.487-493
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• 2012

We present interferometric modulators that reproduce RGB colors through the selective actuation of mechanically coupled mirror arrays having identical air gaps. The conventional transmittive interferometric modulators need additional backlights, which leads to high power consumption. The previous reflective interferometric modulators using ambient lights need three different air gaps for reproducing the three RGB colors, thus giving rise to process complexity. For process simplicity, we propose the use of reflective interferometric modulators that are capable of producing green, blue, red, and black colors with the aid of mechanically coupled mirrors with identical air gaps. In an experimental study, the present interferometric modulators reproduce green, blue, and red colors at the switching modes (000), (010), and (101). The spectrum peaks for the colors are measured at the wavelengths $511{\pm}5nm$, $478{\pm}3nm$, and $644{\pm}9nm$, respectively, with the bandwidths being $60{\pm}1nm$, $45{\pm}2nm$, and $105{\pm}4nm$, respectively; further, the maximum intensities of the colors are $77{\pm}5%$, $73{\pm}2%$, and $81{\pm}5%$, respectively. The black spectrum is measured below the intensity of $27{\pm}0%$. Thus, we experimentally demonstrate the color reproduction capability of interferometric modulators fabricated by using a simple process.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.2
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• pp.25-34
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• 2010

This paper proposed a high-speed voltage-controlled ring-oscillator(VCRO) using a frequency doubling technique. The design of the proposed oscillator has been based on TSMC 0.18um 1.8V CMOS technology. The frequency doubling technique is achieved by AND-OR operations with 4 signals which have $90^{\circ}$ phase difference one another in one cycle. The proposed technique has been implemented using a 4-stage differential oscillator compose of differential latched inverters and NAND gates for AND and OR operations. The differential ring-oscillator can generate 4 output signals, which are $90^{\circ}$ out-of-phase one another, with low phase noise. The ANP-OR operations needed in the proposed technique are implemented using NAND gates, which is more area-efficient and provides faster switching speed than using NOR gates. Simulation results show that the proposed, VCRO operates in the frequency range of 3.72 GHz to 8 GHz with power consumption of 4.7mW at 4GHz and phase noise of ~-86.79dBc/Hz at 1MHz offset. Therefore, the proposed oscillator demonstrates superior performance compared with previous high-speed voltage-controlled ring-oscillators and can be used to build high-performance frequency synthesizers and phase-locked loops for radio-frequency applications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.5
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• pp.40-49
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• 2008

A Frequency synthesizer for mobile-DTV applications is implemented using $0.18{\mu}m$ CMOS process with 1.8V supply. PMOS transistors are chosen for VCO core to reduce phase noise. The measurement result of VCO frequency range is 800MHz-1.67GHz using switchable inductors, capacitors and varactors. We use varactor bias technique for the improvement of VCO gain linearity, and the number of varactor biasing are minimized as two. VCO gain deterioration is also improved by using the varactor switching technique. The VCO gain and interval of VCO gain are maintained as low and improved using the VCO frequency calibration block. The sigma-delta modulator for fractional divider is designed by the co-simualtion method for accuracy and efficiency improvement. The VCO, PFD, CP and LF are verified by Cadence Spectre, and the sigma-delta modulator is simulated using Matlab Simulink, ModelSim and HSPICE. The power consumption of the frequency synthesizer is 18mW, and the VCO has 52.1% tuning range according to the VCO maximum output frequency. The VCO phase noise is lower than -100dBc/Hz at 1MHz at 1MHz offset for 1GHz, 1.5GHz, and 2GHz output frequencies.

• The Journal of the Korea Contents Association
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• v.10 no.3
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• pp.294-300
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• 2010

With the development of media technology, UCC actively working through the medium of the Net, the Internet space, which can influence politics instead of TV is drawing attention as the new leading media. As the one-sided media influence of TV is dwindling in the times of the Internet, the hegemony of the media is rapidly changing into UCC marked by two-way interaction. Especially, UCC has the characteristic that it has changed the people performing a role as the receptor of the media into the agent of enormous political influence as well as the freshness specific to its contents. This study was intended to investigate the types of diverse political influences of UCC in political practice as well as daily politics with a focus on the fact that it can newly project the world led by the media and their changes and exercise strong power in changing the society. Therefore, it attempted to investigate the political influence and ripple effect that UCC can exert by attempting to analyze what political influence UCC can exercise at diverse political situations including election. As a result, UCC led to four situations such as incentive-exploding type, issue-leading type, dispersion-switching type, direction-obeying type. This can be said to lead to the positive effect at the political field, such as implementing direct democracy through digital technology.

• Journal of Sensor Science and Technology
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• v.11 no.1
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• pp.48-53
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• 2002

Ferroelectric $Pb_{0.99}[(Zr_{0.6}Sn_{0.4})_{1-x}Ti_x]_{0.98}Nb_{0.02}O_3$(PNZST) thin films were deposited by a RF magnetron sputtering on $(La_{0.5}Sr_{0.5})CoO_3$(LSCO)/Pt/Ti/$SiO_2$/Si substrate using a PNZST target with excess PbO of 10 mole%. The crystallinity and electrical properties of the thin films with various composition ratio were investigated. The thin films deposited at the substrate temperature of $500^{\circ}C$ and the power of 80 W were crystallized to a perovskite phase after rapid thermal annealing(RTA) at $650^{\circ}C$ for 10 seconds in air. A PNZST thin films with Ti of 10 mole% showed the good crystallinity and ferroelectric properties. The remanent polarization and coercive field of the PNZST capacitor were about $20\;{\mu}C/cm^2$ and 50 kV/cm, respectively. The reduction of the polarization after $2.2{\times}10^9$ switching cycles was less than 10%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5541-5549
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• 2015

This paper introduces a safer and more power efficient heater by using induction heating, to apply to the semiconductor wafer fabrication exhaust gas cleaning system. The exhaust gas cleaning system is currently made with filament heater that generates an endothermic reaction of N2 gas for the removal of moisture. Induction theory, through the bases of theoretical optimization and electronic implementation, is applied in the design of the induction heater specifically for the semiconductor wafer exhaust system. The new induction heating design provides a solution to the issues with the current energy inefficient, unreliable, and unsafe design. A robust and calibrated design of the induction heater is used to optimize the energy consumption. Optimization is based on the calibrated ZVS induction circuit design specified by the resonant frequency of the exhaust pipe. The fail-safe energy limiter embedded in the system uses a voltage regulator through the feedback of the MOSFET control, which allows the system performance to operate within the specification of the N2 Heater unit. A specification and performance comparison from current conventional filament heater is made with the calibrated induction heater design for numerical analysis and the proof of a better design.

• Korean Journal of Optics and Photonics
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• v.16 no.3
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• pp.287-294
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• 2005

In this paper, an optical true time-delay (TTD) for two-dimensional (2-D) phased array antennas (PAAs), composed of a multi-wavelength optical source and a fiber optic delay line matrix consisting of $2\times2$ optical switches with optical fiber connected between cross ports, has been proposed. A 2-bit $\times4-bit$ optical TTD for 10-GHz 2-D PAAs has been implemented by cascading a wavelength dependent TTD (WD-TTD) and a wavelength independent TTD (WI-TTD). The unit time delay for WD-TTD and WI-TTD have been chosen as ${\Delta}T=12ps$ and $\Delta\tau=6ps$, respectively. Time delay have been measured at all radiation angles. The maximum delay error for WD-TTD was measured to be 3 ps due to jitter incurred from gain switching. For the case of WI-TTD, error was within ${\pm}\;1\;ps$. The proposed optical TTD for a 2-D PAA has the following advantages: 1) higher gain compared to one-dimensional linear PAAs, 2) stabilization of optical power and wavelength by using a multi-wavelength optical source, and 3) fast beam scan and simple operation due to electronic control of the $2\times2$ optical switches matrix on a column-by-column basis.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.7
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• pp.473-478
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• 2001

Ferroelectric P $b_{0.99}$［(Z $r_{0}$ 6S $n_{0.4}$)/0.9/ $Ti_{0.1}$］0.98/N $b_{0.02}$ $O_3$(PNZST) thin films were deposited by a RF magnetron sputtering on L $a_{0.5}$S $r_{0.5}$Co $O_3$(LSCO)/Pt/Ti/ $SiO_2$/Si substrate using a PNZST target with excess PbO of 10 mole%. The crystallinity and electrical properties of the thin films annealed at various temperature and time were investigated. The thin films deposited at the substrate temperature of 500 $^{\circ}C$ and the power of 80 W were crystallized to a perovskite phase after rapid thermal annealing(RTA). The thin films annealed at 650 $^{\circ}C$ for 10 seconds in air exhibited the good crystal structures. The remanent polarization and coercive field of the PNZST capacitor were about 20 $\mu$C/$\textrm{cm}^2$ and 50 kV/cm, respectively. The reduction of the polarization after 2.2$\times$10$^{9}$ switching cycles was less than 10 %..10 %......

• The KIPS Transactions:PartD
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• v.15D no.6
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• pp.755-766
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• 2008

Recently, NAND flash memory is becoming into the spotlight as a next-generation storage device because of its small size, fast speed, low power consumption, and etc. compared to the hard disk. However, due to the distinct characteristics such as erase-before-write architecture, asymmetric operation speed and unit, disk-based systems and applications may result in severe performance degradation when directly implementing them on NAND flash memory. Especially when a B-tree is implemented on NAND flash memory, intensive overwrite operations may be caused by record inserting, deleting, and reorganizing. These may result in severe performance degradation. Although ${\mu}$-tree has been proposed in order to overcome this problem, it suffers from frequent node split and rapid increment of its height. In this paper, we propose Log-Structured B-Tree(LSB-Tree) where the corresponding log node to a leaf node is allocated for update operation and then the modified data in the log node is stored at only one write operation. LSB-tree reduces additional write operations by deferring the change of parent nodes. Also, it reduces the write operation by switching a log node to a new leaf node when inserting the data sequentially by the key order. Finally, we show that LSB-tree yields a better performance on NAND flash memory by comparing it to ${\mu}$-tree through various experiments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.66-73
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• 2002

This paper presents ZVZCS(Zero-Voltage and Zero-Current Switching) Three Level DC/DC Converter without primary freewheeling diodes. The new converter presented in this paper used a phase shirt control with a flying capacitor in the primary side to achieve ZVS for the outer switches. A secondary anxiliary circuit which consists of one small capacitor, two small diodes and one coupled inductor, is added in the secondary to provide ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages include simple secondary auxiliary circuit topology, high efficiency, and low cost make the new converter attractive for high power applications. Also the circulating current flows through the circuit so that it causes the needless coduction loss to be occurred in the devices and the transformer of the circuit The new converter has no primary auxiliary diodes for freewheeling current. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1[㎾］ 50[KHz］IGBT based experimental circuit.