• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.9
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• pp.800-807
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• 2006

To enhance the conversion speed more fast, we separate the determination process of MSB and LSB with the two independent ADC circuits of the Incremental Sigma Delta ADC. After the 1st Incremental Sigma Delta ADC conversion finished, the 2nd Incremental Sigma Delta ADC conversion start while the 1st Incremental Sigma Delta ADC work on the next input. By determining the MSB and the LSB independently, the ADC conversion speed is improved by two times better than the conventional Extended Counting Incremental Sigma Delta ADC. In processing the 2nd Incremental Sigma Delta ADC, the inverting sample/hold circuit inverts the input the 2nd Incremental Sigma Delta ADC, which is the output of switched capacitor integrator within the 1st Incremental Sigma Delta ADC block. The increased active area is relatively small by the added analog circuit, because the digital circuit area is more large than analog. In this paper, a 14 bit Extended Counting Incremental Sigma-Delta ADC is implemented in $0.25{\mu}m$ CMOS process with a single 2.5 V supply voltage. The conversion speed is about 150 Ksamples/sec at a clock rate of 25 MHz. The 1 MSB is 0.02 V. The active area is $0.50\;x\;0.35mm^{2}$. The averaged power consumption is 1.7 mW.

• Journal of the Korean Ceramic Society
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• v.38 no.4
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• pp.325-330
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• 2001

고상반응법으로 이론 밀도의 약 97%의 소결 밀도를 갖는 N $d_{1-x}$S $r_{x}$G $a_{1-x}$M $g_{x}$ $O_{3{\delta}}$(x=0, 0.03, 0.07, 0.1) 고체전해질을 제조하였다. X선 회절 분석 결과, x=0.03일 때의 X선 회절도는 순수한 NdGa $O_3$와 같았으나, x=0.07, 0.1일 때에는 불순물이 나타났다. 교류 복소임피던스는 4$50^{\circ}C$~90$0^{\circ}C$의 온도 범위에서 공기 중에서 측정하였으며, 각 조성에 대하여 상호 비교 분석하기 위하여 복소비저항 스펙트럼으로 변환하여 해석하였다. 전기전도도는 N $d_{0.93}$S $r_{0.07}$G $a_{0.93}$M $g_{0.07}$ $O_{0.97}$(x=0.07) 시편이 90$0^{\circ}C$에서 6$\times$$10^{-3}$ S$cm^{-1}$ /로 가장 우수하였으며, 활성화 에너지는 저온 영역에서는 1 eV, 고온 영역에서는 0.74 eV이었다.다.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.1
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• pp.10-17
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• 2012

This paper presents a clock regenerator using two $2^{nd}$ order ${\sum}-{\Delta}$ (sigma-delta) modulators for wide range of dividing ratio as defined in HDMI standard. The proposed circuit adopts a fractional-N frequency synthesis architecture for PLL-based clock regeneration. By converting the integer and decimal part of the N and CTS values in HDMI format and processing separately at two different ${\sum}-{\Delta}$ modulators, the proposed circuit covers a very wide range of the dividing ratio as HDMI standard. The circuit is fabricated using 0.18 ${\mu}m$ CMOS and shows 13 mW power consumption with an on-chip loop filter implementation.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.117.1-117.1
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• 2000

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.135-139
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• 2008

In this paper, tunable SC(switched capacitor) 2nd order bandpass $\Sigma-\Delta$(Sigma-Delta) modulator with novel architecture that can adjust the IF band center frequency by one coefficient value is proposed for data conversion in the IF(Intermediate Frequency) band. Its architecture can optionally adjust all the 2nd order noise transfer function in comparison with the conventional architecture. In order to adjust the center frequency, the conventional architecture needs the two variable coefficient values, basic clock and eight clocks. On the other hand, the proposed architecture can adjust the center frequency by one variable coefficient value and basic clock only.

• Journal of Magnetics
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• v.18 no.2
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• pp.150-154
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• 2013

$La_{1-z}Nd_z(Fe_{0.88}Si_{0.12})_{13}$ and their hydrides were investigated to obtain large magnetocaloric effects (MCEs) in a wide temperature range, including room temperature, for applications in magnetic refrigents. Since the magnetization change due to the itinerant-electron metamagentic (IEM) transition for $La_{1-z}Nd_z(Fe_{0.88}Si_{0.12})_{13}$ becomes larger with increasing z, the isothermal magnetic entropy change ${\Delta}S_m$ and the relative cooling power (RCP) are enhanced. In addition, the Curie temperatrue $T_C$ of $La_{0.8}Nd_{0.2}(Fe_{0.88}Si_{0.12})_{13}$ is increased from 193 to 319 K by hydrogen absorption, with the IEM transition. The maximum value of $-{\Delta}S_m$, $-{\Delta}S{_m}^{max}$, in a magnetic field change of 2 T for $La_{0.8}Nd_{0.2}(Fe_{0.88}Si_{0.12})_{13}H_{1.1}$ is about 23 J/kg K at $T_C$ = 288 K, which is larger than that of 19 J/kg K at $T_C$ = 276 K for $La(Fe_{0.88}Si_{0.12})_{13}H_{1.0}$. The value of RCP = 179 J/kg of the former is also larger than 160 J/kg of the latter. It is concluded that the partial substitution of Nd improves MCEs in a wide temperautre range, including room temperature.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.54-61
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• 2009

This paper proposes the 2nd-order SDSDM (Space Dithered Sigma-Delta Modulation) for performance improvement of a buck converter. The PWM (Pulse Width Modulation) has a drawback in that power spectrum tends to be concentrated around the switching frequency. The resulting harmonic spikes cause a EMI(Electromagnetic Interference) and switching loss in semiconductor, etc. The 1st-order SDSDM scheme is a kind of DSDM for reducing these harmonic spikes. In this scheme, a switching frequency is spread through random dither generator placed on input part. In experimental result, the proposed 2nd-order SDSDM is confirmed by applying to a buck converter.

• Progress in Superconductivity and Cryogenics
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• v.11 no.2
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• pp.1-6
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• 2009

We report a successful fabrication of $high-J_c\;NdBa_2Cu_3O_{7-{\delta}}$ (NdBCO) films on $SrTiO_3$(STO) (100) substrates by pulsed laser deposition (PLD) in a relatively wide processing window. Under various oxygen pressures controlled by either 1%$O_2$/Ar mixture gas or pure $O_2$ gas, strongly c-axis oriented NdBCO films were grown at the substrate temperature $(T_s)\;of\;800^{\circ}C$ in 800 mTorr with 1%$O_2$/Ar gas and also in 400 and 800 mTorr with pure $O_2$ gas. These samples exhibited $T_c$ values over 90K and $J_c$ values of $2.8-3.5MA/cm^2$ at 77K in self-field (77K, sf). On the other hand, $J_c$ values over $1A/cm^2$ were obtained at the temperature regions of $700-830^{\circ}C$ in 800 mTorr with 1%$O_2$/Ar gas at those of $750-830^{\circ}C$ in 800 mTorr with pure $O_2$ gas. Unlike previous reports, resent results support that the PLD processing window for high-Jc NdBCO films is not narrow.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.121-123
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• 2002

Fast response characteristics of twisted nematic liquid crystal display (TN-LCD) cell with different nematic liquid crystals (NLCs) and cell gap on a rubbed polyimide (PI) surface were studied. High transmittance and fast response time of the TN-LCD on the rubbed PI surface were achieved by using high birefringence ($\Delta$ n) and low cell gap. It is considered that the transmittance and response time of the TN-LCD on the rubbed PI surface decreased as $\Delta$ nd decrease.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.514-517
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• 2002

We investigated response characteristics of twisted nematic (TN) cell with different nematic liquid crystals (NLCs) and cell gap d on a rubbed polyimide (PI) surface. High transmittance and fast response time of the TN cell on the rubbed PI surface were achieved by using high birefringence (${\Delta}n$) and low cell gap d. The response time of TN cell on the rubbed PI surface was measured 5.1 ms. The transmittance and response time of the TN cell on the rubbed PI surface decreased with decreasing ${\Delta}nd$.