• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.9
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• pp.771-775
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• 2007

In this study, in order to develop low temperature sintering ceramics for thickness vibration mode multilayer piezoelectric transformer, $PbTiO_3$ system ceramics were fabricated using $Na_2CO_3,\;Li_2CO_3,\;MnO_2\;and\;Bi_2O_3$ as sintering aids and their dielectric and piezoeletric properties were investigated according to the amount of $Bi_2O_3$ addition. At the sintering temperature of $900^{\circ}C\;and\;Bi_2O_3$ addition of 0.1 wt%, density, grain size, thickness vibration mode eletromechanical coupling factor($k_t$), thickness vibration mode mechanical quality factor($Q_{mt}$) and dielecteic constant(${\varepsilon}_r$) showed the optimum value of $6.94g/cm^3,\;2.413{\mu}m$, 0.497, 3,162 and 209, respectively, for thickness vibration mode multilayer piezoelectric transformer application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.214-216
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• 2006

In this study, in order to develop the composition ceramics for low loss and low temperature sintering multilayer piezoelectric actuator, PMN-PZN-PZT ceramics were fabricated using two stage calcination method and $Li_2CO_3$, $Bi_2O_3$ and CuO as sintering aids and their piezoelectric characteristics were investigated according to the 2nd calcination and sintering temperature. At the calcination temperature of $750^{\circ}C$ and sintering temperature of $930^{\circ}C$, density, electromechanical coupling factor ($k_p$), mechanical quality factor ($Q_m$), Dielectric constant (${\varepsilon}_r$) and piezoelectric constant ($d_{33}$) of specimen showed the optimum value of $7.94g/cm^2$ 0.581, 1554, 1555 and 356pC/N, respectively for multilayer piezoelectric actuator application.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.3
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• pp.182-188
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• 2001

A solenoid-type MEMS inductor with a quality factor over 10 at 2 GHz has been developed using an electroplating technique. The integrated spiral inductor has a low Q factor due to substrate loss and skin effects. It also occupies a large area compared to the solenoid-type inductor. The direction of flux of the solenoid-type inductor is parallel to the substrate, which can lower the substrate loss and other interference with integrated passive components. To estimate the characteristics of the proposed inductor over a high frequency range, the 3D FEM (Finite Element Method) simulation is used by using the HFSS at the Ansoft corporation. The electroplated solenoid-type inductor is fabricated on a glass substrate step by step by using photolithography and copper electroplating. The fabrication process to improve the quality factor of the inductor is also developed. The achieved inductance varies within a range from 0.5 nH to 2.8 nH, and the maximum Q factor is over 10.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.157-160
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• 2001

We have investigated the Dielectric and Piezoelectric properties of $xPb(R_{1/2}Ta_{1/2})O_3-(1-x)Pb(Zr_{0.52}Ti_{0.48})O_3$ (R=Al,Y) solid solutions in which R ions are substituted for Al and Y ions. The maximum value of electromechanical coupling factor kp of 55% and 51% were obtained at the composition of 5mol% PAT and 5mol% PYT. However mechanical quality factor$(Q_m)$ had a minimum value of 44 and 69 at the composition of 5mol% PAT and 5mol% PYT. Also, the maximum value of piezoelectctric constant of $d_{33}(329[pC/N])$ and $d_{33}(310[pC/N])$ were obtained at the composition of 5mol% PAT and 5mol% PYT.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.356-360
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• 2002

The piezoelectric properties of $0.05Pb(Al_{0.5}Nb_{0.5})O_3-0.95Pb(Zr_{0.52}Ti_{0.48})O_3+0.7wt%Nb_2O_5+o.5wt%MnO_2$ ceramics with the additive of BaCO$_3$were investigated. As the addition of BaCO$_3$increased from 0 to 0.4 wt%, the dielectric constant ($\epsilon^T _{33}$), piezoelectric constant ($d_33$), electromechanical coupling factor ($k_p$), and mechanical quality factor ($Q_m$) increased, while the dielectric loss ($tan\delta$) decreased. The highest piezoelectric and dielectric properties were observed at $1200^{\circ}C$ of the sintered temperature with 0.4 wt% of $BaCO_3$, and the properties of $d_33$, $k_p$, and $Q_m$ were 339 pC/N, 60% and 1754, respectively.

• Progress in Medical Physics
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• v.20 no.1
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• pp.7-13
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• 2009

This work is for the preliminary study for the calibration of an $^{192}Ir$ brachytherapy source based on an absorbed dose to water standards. In order to calibrate brachytherapy sources based on absorbed dose to water standards using a clyndirical ionization chamber, the beam quality correction factor $k_{Q,Q_0}$ is needed. In this study $k_{Q,Q_0}s$ were determined by both Monte carlo simulation and semiexperimental methods because of the realistic difficulties to use primary standards to measure an absolute dose at a specified distance. The 5 different serial numbers of the PTW30013 chamber type were selected for this study. While chamber to chamber variations ran up to maximum 4.0% with the generic $k^{gen}_{Q,Q_0}$, the chamber to chamber variations were within a maximum deviation of 0.5% with the individual $k^{ind}_{Q,Q_0}$. The results show why and how important ionization chambers must be calibrated individually for the calibration of $^{192}Ir$ brachytherapy sources based on absorbed dose to water standards. We hope that in the near future users will be able to calibrate the brachytherapy sources in terms of an absorbed dose to water, the quantity of interest in the treatment, instead of an air kerma strength just as the calibration in the high energy photon and electron beam.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.585-587
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• 2009

A large diameter slot waveguide made backward wave oscillator is investigated experimentally. The parameters of slow wave structure are chosen so that the oscillation frequency is about 20 GHz. Plasma is produced by the beam and it has favorable effects on beam propagation and Cherncov oscillation. The output power strongly enhanced when the guiding magnetic field approaches to the fundamental electron cyclotron resonance.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.547-548
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• 2006

In this paper, cost effective parallel-branch inductor has been proposed and developed in order to increase the quality factor of the conventional spiral inductor. This parallel-branch inductor is composed of only two metals. The presented parallel-branch inductor shows 12% improvement in the quality factor with the same area as the conventional inductor. Also, we improve the parallel-branch inductor for high frequency applications.

• Journal of electromagnetic engineering and science
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• v.14 no.2
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• pp.47-53
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• 2014

This paper presents a high gain and high harmonic rejection low-noise amplifier (LNA) for software-defined radio receiver. This LNA exploits the high quality factor (Q) series resonance technique. High Q series resonance can amplify the in-band signal voltage and attenuate the out-band signals. This is achieved by a source impedance transformation. This technique does not consume power and can easily support multiband operation. The chip is fabricated in a $0.13-{\mu}m$ CMOS. It supports four bands (640, 710, 830, and 1,070MHz). The measured forward gain ($S_{21}$) is between 12.1 and 17.4 dB and the noise figure is between 2.7 and 3.3 dB. The IIP3 measures between -5.7 and -10.8 dBm, and the third harmonic rejection ratios are more than 30 dB. The LNA consumes 9.6 mW from a 1.2-V supply.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.629-632
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• 1998

This paper presents a new and simple technique to realize high Q inductor on low resistivity silicon wafer with 6 $\Omega$.cm. This technique is very compatible with bipolar and CMOS standard silicon process. By forming the deep and narrow trenches on the low resistivity wafer substrate under inductor pattern, oxidizing and filling with undoped polysilicon, the low resistivity silicon wafer acts as high resistivity wafer being suitable for the fabrication of high Q inductor. By using this technique the quality factor (Q) for 8-turn spiral inductor was improved up to max. 10.3 at 2 ㎓ with 3.0 $\mu\textrm{m}$ of metal thickness. The experiment results show that Q on low resistivity silicon wafer with the trench technique have been improved more than 2 times compared to the conventional low resistivity silicon wafer without trenches.