• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.1
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• pp.35-43
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• 2022

In this paper, a study was conducted to produce 20W by combining a 10W MMIC and raising the unit power amplifier to 100W SSPA by combining the 8-way spatial coupler. SSPA requires low-loss, high-efficiency coupling techniques to meet high output with the output of a single element relatively low compared to TWTA. Designed and produced in this paper, the SSPA was manufactured as a 100W SSPA by mounting eight 20W high-power amplification modules in an 8-way spatial coupler with a reflection loss of 20dB or more and an excellent coupling efficiency of 94% or more. When -10dBm was applied, it was 112.2~169.8W at 20kHz 20%, 125.9~173.8W at 400kHz 40%, 117.5~162.2W at 800kHz 40%, showing performance of over 60dB and over 100W in all three PRF conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.1
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• pp.35-39
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• 2006

In this study, in order to develop the multilayer piezoelectric actuator and ultrasonic resonator, PMN-PNN-PZT ceramics were fabricated by sintering with $Li_2CO_3-Na_2CO_3$ as sintering aids at $950^{\circ}C$ and their piezoelectric and dielectric characteristics were investigated as a function of PNN substitution. With increasing PNN substitution, dielectric constant(${\epsilon}_r$), electromechanical coupling factor(kp), and piezoelectric d constant($d_{33}$) were increased to $12 mol\%$ PNN substitution and then showed a tendency to decrease rapidly With increasing PNN substitution, crystal structure changed from tetragonal to rhombohedral at $12 mol\%$ PNN substitution and then secondary phase was appeared and its intensity was increased. At the $12 mol\%$ PNN substituted PMN-PZT composition ceramic sintered at $950^{\circ}C$, density, kp, $d_{33}$ and Qm showed the optimum value of $7.79 g/cm^3$, 0.599, 419 pC/N, and 894, respectively for multilayer piezoelectric actuator application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.63-67
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• 1996

In this paper, effect of MnO$_2$ addition(0, 0.1, 0.2, 0.3, 0.5wt%) on the microstructure, dielectric and piezoelectric properties of [xPMW - (0.15-x) PNN] - [yPT-(0.85-y)PZ] (x=0, 0.01, 0.02, 0.03, 0.05, y = 0.35, 0.40, ().425, 0.45, 0.5) were investigated. When Ti/Zr ratio was 1.0, dielectric and piezoelectric properties were highest value. With PMW 2mol%, dielectric constant, dielectric constant (d$\_$33/, d$\_$31/) and electromechanical coupling factor (kp, k$\_$31/) were highest values of 1995, 479, 186(x10$\^$-12/C/N), 0.61, 0.36, respectively. With the addition of MnO$_2$, dielectric constant, electromechanical coupling factor (kp, k$\_$31/) were decreased, but with 0.3wt% MnO$_2$, eletromechanical coupling factor was highest value of 0.63. With the addition of MnO$_2$, mechanical quality(Q$\_$m/ was increased.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.7 no.4
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• pp.188-194
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• 2014

In this paper, an antenna which has quad band in LTE (0.746 ~ 0.798 GHz), GSM(0.824 ~ 0.960 GHz), DCS(1.71 ~ 1.88 GHz), WCDMA(1.91 ~ 2.17 GHz) is proposed. An antenna size is $122mm{\times}50mm{\times}0.8mm$ on FR4(${\epsilon}_r=4.4$) ground substrate. In the proposed antenna, branch line is applied to the conventional PIFA architecture to achieve multi-bandwidth. Coupling power supply is applied for a wide bandwidth. Result of the measurement is as follows. When the low frequency, the antenna presents gain of 0.93 ~ 1.92dBi, and radiation efficiency of 49.60 ~ 76.35 %, and When the high frequency, gain is 2.19 ~ 4.66dBi, and radiation efficiency is 60.40 ~ 80.01 %, and with a VSWR < 2 (${\leq}-10dB$)measurement results for standard satisfies all band. Judging from the result, proposed multiband antenna is expected to be applied. B4G mobile terminals since the antenna shows an outstanding performance.

• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.257-262
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• 2007

The efficient synthesis of a tetrasaccharide, the suitably protected form of the repeat unit, →2)-α-D-Manp-(1→2)-β-D-Manp-(1→3)-α-D-GlcpNAc-(1→6)-α-D-Manp-(1→, of the O-antigen polysaccharide of the lipopolysaccharide from E. coli O77 has been accomplished. Glycosylation reactions for the coupling of four monosaccharide building blocks of the tetrasaccharide were carried out employing the CB glycoside method, the mannosyl 4-pentenoate/PhSeOTf method, and the glycosyl trichloroacetimidate method with complete stereoselectivities in excellent yields.

• International Journal of Advanced Culture Technology
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• v.7 no.1
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• pp.225-230
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• 2019

In order to improve performance for the size of the rat-race ring coupler, the CCL is used for the realization as the delay line. As realizing lower coupling coefficient, the ratio of the size-reduction for the CCL is enhanced. The CCL is alternated with ${\lambda}_g/4$ of the rat-race ring, and optimized two CCLs are inserted for the size-reduction. the coupling coefficient is 0.2, and electrical lengths of each CCL are $28.2^{\circ}$ and $21.7^{\circ}$. Designed rat-race ring using the CCL has the size of $18.76{\times}20.45mm^2$ and the size-reduction ratio of fabricated rat-race ring using the CCL has 76.8%. Also, fabricated rat-race ring is measured the insertion loss of 3.20dB at the center frequency of 2.45GHz and the 20dB bandwidth is 24.04%. Differenced magnitude and phase between threw port and coupled port are measured 0.1dB and $177.4^{\circ}$, respectively. These performances are almost same compared with the conventional rat-race ring. Suggested application of the CCL can be used various devices and circuits for the size-reduction.

• Progress in Superconductivity
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• v.1 no.1
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• pp.1-8
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• 1999

The magnetization and/or resistivity of high $T_c$ superconductors ($YBa_2Cu_3O_{7-\delta}$(YBCO) single crystal, $Bi_2Sr_2CaCu_2O_8$ (Bi-2212) single crystal, $Tl_2Ba_2CaCu_2O_8$ (Tl-2212) film, $HgBa_2Ca_2Cu_3O_8$ (Hg-1223) film) have been measured as a function of magnetic field H and temperature T. The extracted fluctuation part of the magnetization and conductivity exhibits a critical behavior consistent with the three-dimensional XY model. The dynamic critical exponent z does not sensitively vary with a type of the superconductors. The value of z ranges from 1.5 to $1.8{\pm}0.1$. However, the static critical exponent ${\nu}$ is the most largely increased in Tl-2212 that has a weaker interlayer coupling strength than YBCO; the value of ${\nu}$ is 0.669, 0.909, 1.19, and 1.338 for YBCO, Bi-2212, Hg-1223, and Tl-2212 respectively. The results indicate that the weak interlayer coupling along the c-axis of high $T_c$ superconductors near $T_c$ does not influence the dynamic critical exponent z (the same value of superfluid $^4He$), but significantly increases the static critical exponent ${\nu}$.

• Journal of the Korean Ceramic Society
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• v.32 no.3
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• pp.378-384
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• 1995

Effects of $La_2O_3$, $MnO_2$ on the dielectric and piezoelectric properties of $0.02Pb(Y_{2/3}W_{1/3}O_3-0.98Pb(Zr_{0.52}Ti_{0.48})O_3$ system were investigated. The addition of La2O3 to the system enhanced electromechanical coupling factor (kp), piezoelectric constant (d33), but hardly changed mechanical quality factor (Qm). On the other hand, the addition of $MnO_2$ increased Qm significantly, but did not degrade kp and d33 so much. The piezoelectric properties of $0.02Pb(Y_{2/3}W_{1/3}O_3-0.98Pb(Zr_{0.52}Ti_{0.48})O_3$ containing 0.1wt% $La_2O_3$, 0.4wt% $MnO_2$ were very good and kp, d33, Qm were 55%, 350$\times$10-12C/N, 780, respectively. The size of the grains was proportional to the change of c/a (tetragonality) ratio caused by the addition of $La_2O_3$ and $MnO_2$, and dielectric, piezoelectric properties were sensitive to the amountof pyrochrole phase.

• Journal of the Korean Magnetic Resonance Society
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• v.25 no.1
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• pp.1-7
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• 2021

Employing of 13C stable-isotopes in NMR metabolomics can give unique splitting patterns and coupling constants information originated from 13C-13C coupling interaction that provide an important structural information regarding the cellular metabolic process. But it has been known that an undesirable signal distortion in 2D heteronuclear correlation study, due to 13C-13C interaction, hampers an analysis of the coupling information. Recently, we proposed J-scaled distortion-free heteronuclear single-quantum coherence (HSQC) sequence which provides a distortion-free 13C-13C coupling information with a selective resolution enhancement of JCC splitting. In this paper, we dicuss theoretical aspect and practical feature of J-scaled HSQC pulse sequence. The conceptual explanation of orgin of the signal distortion by 13C-13C coupling interaction and design of J-scaled HSQC through exemplified results are provided in brief.

• Bulletin of the Korean Chemical Society
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• v.17 no.5
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• pp.452-457
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• 1996

The effects caused by the ionization on the electronic structure and geometry on C60 are studied by the modified Su-Schriffer-Heeger (SSH) model Hamiltonian. After the ionization of C60, the bond structure of the singly charged C60 cation is deformed from Ih symmetry of the neutral C60 to D5d, C1, and C2, which is dependent upon the change of the electron-phonon coupling strength. The electronic structure of the C60+ cation ground state undergoes Jahn-Teller distortion in the weak electron-phonon coupling region, while self-localized states occur in the intermediate electron-phonon region, but delocalized electronic states appear again in the strong electron-phonon region. In the realistic strength of the electron-phonon coupling in C60, the bond structure of C60+ shows the layer structure of the bond distortion and a polaron-like state is formed.