• Transactions on Electrical and Electronic Materials
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• v.5 no.2
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• pp.76-80
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• 2004

Piezoelectric and dielectric properties as functions of x and y mole ratio in yPb(ZrxTil-x)O$_3$(1-y)Pb(Mn$\_$1/3/Nb/2/3/)O$_3$, ceramics, PZT-PMN, are investigated for large displacement piezoelectric devices. From the experimental results, when y is 0.95 and x is 0.505, the piezoelectric and dielectric properties are maximum, that is, electromechanical coupling coefficient(kp), piezoelectric strain constant(d$\_$33/), permittivity($\varepsilon$$\_$33/$\^$T//$\varepsilon$$\_$0/), and Curie temperature are 58 %, 272 pC/N, 1520 and about 350$^{\circ}C$, respectively. Also, when y is 0.90 and x is 0.50, their properties are 56 %, 242 pC/N, 1220, and 290$^{\circ}C$, respectively. As MgO dopant is added from 0 wt% to 1 wt%, kp increases to 63 % and Qm decreases to 500 at the MgO dopant of 0.1 wt%, and then kp decreases to 57 % as MgO is added.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.59-61
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• 2005

In this paper, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, $Pb[(Mn_{1/3},Nb_{2/3})_{0.07}(Zn_{1/3}Nb_{2/3})_a(Zr_{0.48}Ti_{0.52})_{1-0.07-a}O_3]$ ceramics were manufactured with the variations of PZN from 2 to 14mol% and their dielectric and piezoelectric properties were investigated. Sintering temperature was varied from 910 to $1000^{\circ}C$. At 8mol% PZN substituted specimen sintered at $970^{\circ}C$, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant and peizoelectric constant($d_{33}$) showed the optimal values of 0.536, 1803, 1551 and 328[pC/N), respectively, for multilayer piezoelectric transformer application.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.3
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• pp.31-37
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• 2015

In this paper, newly proposed dual-band microstrip antennas using stacked inverted-L-shaped parasitic elements are presented for GPS $L_1(1.575GHz)$ and $L_2(1.227GHz)$ bands. For making dual band which has large interval, ${\lambda}/4$($L_1$ band) inverted-L-shaped parasitic elements were stacked at both side of radiation apertures on the half-wavelength($L_2$ band) patch antennas. The resonance in the parasitic elements occurs through coupling to the patch. Next, due to using circular polarization at GPS, ${\lambda}/4$($L_1$ band) inverted-L-shaped parasitic elements was stacked using sequential rotation technique on the patch and both side of the diagonal corners of the antenna were eliminated to make dual-band circular polarization. The designed circular polarized antenna's dimensions are $0.43{\lambda}L{\times}0.43{\lambda}L{\times}0.06{\lambda}L$ (${\lambda}L$ is the free-space wavelength at 1.227 GHz). Measured -10 dB bandwidths was 120 MHz(7.6%) and 82.5 MHz(6.7%) at GPS $L_1$ and $L_2$ bands. and 3 dB axial ration bandwidths are 172 MHz(10.9%) and 25 MHz(2.03%), respectively. All of these cover the respective required system bandwidths. Within each of the designed bands, broadside radiation patterns were observed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.6
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• pp.578-583
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• 2016

In this paper, we propose a multi-mode wireless power transfer (WPT) system with a dual loop structure. The proposed multi-mode WPT system consist of outer loop module which can operate at two different frequency bands including 6.78 MHz magnetic resonance WPT mode and 13.56 MHz near field communication (NFC) mode and inner loop module connected with outer loop which can operate at two different frequency bands including WPC mode and PMA mode based on inductive coupling standards. In order to be able to embed this system into smartphone battery back cover, the electrical designs are optimized and then the size was fixed $45{\times}90{\times}0.35mm3$ (including ferrite sheet) which is the same commercial smartphone. The proposed multi-mode WPT module can cover WPC and PMA mode based on inductive coupling. Moreover, it has more than 20 dB return loss characteristics at two different frequency bands including 6.78 MHz and 13.56 MHz, and shows more than 70 % transfer efficiency between resonant coils at 6.78 MHz in magnetic resonant charging environment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.53-58
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• 2008

This paper designs sigma-delta D/A Converter with a high resolution and low power consumption. It reorganizes the input data along LJ, RJ, I2S mode and bit mode to the output data of A/D converter. The D/A converter decodes the original analog signal through HBF, Hold and 5th CIFB(Cascaded Integrators with distributed Feedback as well as distributed input coupling) sigma-delta modulation blocks. It uses repeatedly the addition operation in instead of the multiply operation for the chip area and the performance. Also, the half band filters of similar architecture composed the one block and it used the sample-hold block instead of the sinc filter. We supposed simple D/A Converter decreased in area. The filters of the block analyzed using the matlab tool. The top block designed using the top-down method by verilog language. The designed block is fabricated using Samsung 0.35um CMOS standard cell library. The chip area is 1500*1500um.

• ETRI Journal
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• v.31 no.3
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• pp.254-262
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• 2009

This paper presents a novel simple filter design method based on a parallel short-ended coupled-line structure with capacitive loading for size reduction and ultra-broad rejection of spurious passbands. In addition, the introduction of a cross-coupling capacitor into the miniaturized coupled-line can create a transmission zero at the second harmonic frequency for better frequency selectivity and attenuation level. The aperture compensation technique is also applied to achieve a strong coupling in the coupled-line section. The influence of using the connecting transmission line to cascade two identical one-stage filters is studied for the first time. Specifically, such a two-stage bandpass filter operating at 2.3 GHz with a fractional bandwidth of 10% was designed and realized with low-temperature co-fired ceramic technology for application in base stations that need high power handling capability. It achieved attenuation in excess of -40 dB up to $4f_0$ and low insertion loss of -1.2 dB with the size of 10 mm ${\times}$ 7 mm ${\times}$ 2.2 mm. The measured and simulated results showed good agreement.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.256-259
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• 2003

In this paper, a design of multi-layered BPF(bandpass filter) using LTCC(Low Temperature Co-fired Ceramic) process by a lumped-elements is proposed for SOP(system-on-a-chip) of wireless communication systems. The proposed BPF improved a characteristic of rejection band to build an attenuation pole caused by structurally adjacent co-inductance and coupling. The simulation data shows a bandwidth of 90MHz from a center frequency of 2.4GHz, a return loss of 27dB, an insertion loss of 3.2dB, and an attenuation of at least 20dBc at $f_0{\pm}250MHz$. Simulations have used serenade circuit simulation and HFSS EM simulation.

• Journal of the Korean Institute of Telematics and Electronics
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• v.13 no.1
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• pp.16-22
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• 1976

Broadband operation of Y-junction microstrip circulator withlnonreciprocal device is predicteg by Rosenbaum using Bosma's Green function analysis. The anslysis has been modified to enable the scattering matrix and therefore the circulator bandwidth, to be found. The width of the coupling transmission lines is found to be a significant design parameter${\psi}$. A comparison of experimental and theoretical results for the 3-port junction shows that wide lines and a smaller 7.5U than usual disk radius can be used to obtain broadband operation. Circulator operates in the frequency band 5-11 GHz. The obtained maximum insertion loss is 0.5dB and the isolation is more than 15dB.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.131-134
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• 2001

In this paper, the piezoelectric and dielectric properties as a function of x and a in $aPbZr_xTi_{1-x}O_3-(1-a)Pb(Mn_{1/3}Nb_{2/3})O_3$ + ywt%MgO is investigated. As a results, when a is 0.95 and x is 0.505, electromechanical coupling factor$(k_p)$, permittivity${\varepsilon}_33^T/{\varepsilon}_0$, piezoelectric strain constant$(d_{33})$ and mechanical quality factor$(Q_m)$ are 58 %, 1520, 272 pC/N and 1550, respectively. From XRD analysis, when x is 0.505, it is MPB which present rhombohedral and tetragonal phase in same quantity. Also, From SEM observation, when sintering temperature is $1150^{\circ}C$, grain size is about $2\;{\mu}m$. As a results added MgO dopant in the ternary piezoelectric ceramic, when MgO content is 0.1 wt%, $k_p$ increases to 63[%].

• Design & Manufacturing
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• v.15 no.3
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• pp.7-12
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• 2021

Plastic injection molds used for rapid heating and cooling must minimize surface damage due to friction and maintain excellent thermal and low electrical conductivity. Accordingly, various surface treatments are being applied. The properties of Al₂O₃ coating and DLC coating were compared to find the optimal surface treatment method. Al₂O₃ coating was deposited by thermal spray method. DLC films were deposited by sputtering process in room temperature and high temperature PECVD (Plasma enhanced chemical vapor deposition) process in 723 K temperature. For the evaluation of physical properties, the electrical and thermal conductivity including surface hardness, adhesion and wear resistance were analyzed. The electrical resistance of the all coated samples was showed insulation properties of 24 MΩ/sq or more. Especially, the friction coefficient of high temp. DLC coating was the lowest at 0.134.