• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.4 s.107
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• pp.351-357
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• 2006

In this paper, a direct $TM_{01}-TE_{11}$ mode converter of circular waveguide which is used the approximated design method of mode conversion between $TM_{01}$ and $TE_{11}$ modes is designed for radiation with the maximum directivity of high power energy into air (rom high power microwave antenna system. The proposed direct $TM_{01}-TE_{11}$ mode converter is calculated and designed with an approximated method for non-linear function about an extended non-constant serpentine type of circular waveguide. Then, the designed mode converter is optimized by length of 200 mm and efficiency above 95% by FIM simulation and achieved short length and high efficiency of the antenna by results of fabricated and measured characteristics.

• Journal of Nutrition and Health
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• v.33 no.7
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• pp.733-738
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• 2000

The purpose of this study was to investigate the effects of green tea on gene expression of superoxide dismutase(SOD) and glutathione peroxidase(GSH-Px) in rat liver exposed to microwave. Sprague-Dawley male rats with 200$\pm$10g body weight were assigned to normal and microwave exposed groups : microwave exposed groups ; microwave exposed groups were divided two groups : microwave(MW) group which was administrated the distilled water and green tea(GT) group which was administrated the green tea extracts. The rats were irradiated with microwave at frequence of 2.45 GHz for 15 min and then the gene expression in the damaged tissue were investigated at 0.1, 3, 4,6 and 8 days after the microwave irradition to compared with the normal group. The level of SOD gene expression in MW group was lower than the normal group within 6 days but that of GT group as higher than MW group. These results may imply that green tea stimulates SOD expression and there by protecting tissues from free radicals. The GSH-Px gene was expressed a little bit lower than the normal group but that of GT group was expressed to higher lever than MW group from 4 days after irradiation. These results suggest that the administration of green tea extract may activate antioxidative gene expressions such as SOD and GSH-Px in rat and that may help to recover liver tissues from microwave damage by removing hazardous free radicals and oxidized by products from cells.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1942_1943
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• 2009

무선통신 시스템의 소형화와 저가격, 고품질, 다기능 재료 및 첨단 가공 기술과 연계된 필터설계 및 제작 기술에 대한 연구가 활발히 진행 중이다. 그러나 무선통신 시스템은 주파수라는 한정된 자원을 사용하기 때문에 주파수 자원의 효율적 관리를 위한 규제나 방안이 필요하고. 이에 따라서 여러 가지 대책과 방안이 필요로 하고 있다. 그래서 필터의 성능개선을 위한 연구가 본질 적으로 중요하게 되었다. 본 논문은 체비세프(Chebyshev)필터와 버터워스(Butterworth)필터를 이용한 대역통과(band pass) 필터를 제안한다. 이 필터는 안정화된 통과대역과 빠른 주파수 응답을 얻기위해 6차 체비세프필터와 8차 버터워스필터를 결합 하였다. 측정된 대역통과 필터는, 차단 영역을 구분하는 스커트(skirt)특성은 날카롭게(sharp) 되었고 통과대역의 평탄도 또한 개선되어짐을 볼 수 있다. 제안된 필터의 중심주파수는 2.5GHz, 대역폭은 200MHz이고, 대역내 평탄도는 0.5dB, 경사도는 오차가 60dB일때 체비세프는 210MHz, 버터워스는 340MHz, 체비세프-버터워스는 290MHz가 되어 버터워스 보다 좋게 되었으며 극점의 배치도 안정적인 결과를 얻었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.423-426
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• 2001

Recently we have reported that the meander-patterned amorphous FeCoSiB films exhibit large change in their high frequency impedance by applying a strain, suggesting that the films are very attractive for making of a highly sensitive strain sensor elements. In this study, the effect of anisotropy on a change in the impedance of sputtered amorphous film patterns was investigated in the frequency range from 1MHz to 1GHz. As a function of applied strains, the high frequency impedance was extremely changed in the case of film patterns with transverse anisotropy due to excellent magnetomechanical coupling properties. As a summary, the maximum figure of merit f has measured about 2600 in the case of transverse anisotropy, and about 500 in the case of longitudinal anisotropy at 500 MHz. These values of F are approximately more than 1000 times higher than that of a conventional metal strain gauge (F 2) and more than 10 times higher than that of a semiconductor gauge (F 200).

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.4
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• pp.483-490
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• 2009

In this paper, a novel low-damage silicon nitride passivation for 100nm InAlAs/InGaAs MHEMTs has been developed using remote ICPCVD. The silicon nitride deposited by ICPCVD showed higher quality, higher density, and lower hydrogen concentration than those of silicon nitride deposited by PECVD. In particular, we successfully minimized the plasma damage by separating the silicon nitride deposition region remotely from ICP generation region, typically with distance of 34cm. The silicon nitride passivation with remote ICPCVD has been successfully demonstrated on GaAs MHEMTs with minimized damage. The passivated devices showed considerable improvement in DC characteristics and also exhibited excellent RF characteristics($f_T$of 200GHz).The devices with remote ICPCVD passivation of 50nm silicon nitride exhibited 22% improvement(535mS/mm to 654mS/mm) of a maximum extrinsic transconductance($g_{m.max}$) and 20% improvement(551mA/mm to 662mA/mm) of a maximum saturation drain current ($I_{DS.max}$) compared to those of unpassivated ones, respectively. The results achieved in this work demonstrate that remote ICPCVD is a suitable candidate for the next-generation MHEMT passivation technique.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.35-38
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• 2005

The Objective of this work was to design Composite Antenna Structures (CAS) and investigate impact behavior of CAS which was various curvature. This term, CAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constants and tangent loss as well as mechanical properties. For the antenna performance, microstrip antenna layers inserted into structural layers were designed for satellite communication at the resonant frequency of 12.5 GHz and final demonstration article was. After making five kinds of curved CAS, which radii of curvature are flat, 200, 150, 100, 50 mm. The antenna performance changed in accordance with variation of curvature. The Reflection coefficient was independent of curvature but the gain decreased with the radius of curvature. The impact test equipment was Dyna-8250 drop weight tester. The impact characteristic in accordance with curvature is maximum absorb energy is same each other. The impact energy was 8.5 J. For various Impact energy test, five energy levels 3 J, 5 J, 7 J, 10 J, 20 J were used. The performance of impact damaged antenna was estimated by measuring the return loss and the radiation pattern. It was revealed that the performance of antenna was not related to the impact damage. Because the impactor did not damage the patch directly. CAS have good impact stability for the antenna performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.3
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• pp.207-214
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• 2001

The conductive polymers, polyaniline (PANI) emeralidin base and 3,4-polyethylene dioxythiophene(PEDOT) were synthesized and coated on the PET film dealt with acryl type primer to study the electromagnetic shielding effectiveness. When both PANI and PEDOT were coated on the PET film dealt with acryl type priemer, their surface properties such as he adhesive increased. For PANI, when blended with the binder such as PMMA, it adhesive and surface hardness increased, too. The visible light transmittance decreased, while the electromagnetic shielding effectiveness increased, when coated thickness of PANI and PEDOT increased. For PANI, the electromagnetic shielding effectiveness increased as its surface resistance decreased. For PANI, when the surface resistance was 140 Ω/$\square$, the shielding effectiveness was found to be 11 dB in the far field, and 13 dB in the near field at 1 GHz. For PEDOT, when the surface resistance was 200 Ω/$\square$, the shielding effectiveness was found to be 3 dB in the far field, and 7dB in the near field.

• Proceedings of the KSRS Conference
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• 2008.03a
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• pp.25-28
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• 2008

본 논문에서는 GB-SAR의 간섭기법을 이용하여 물체의 변위 측정에 대한 정밀도를 조사하였으며, 또한 대기보정을 거친 후 정밀도의 변화에 대해서 확인하였다. GB-SAR 시스템에서 안테나는 중심주파수 5.3 GHz, 밴드 폭 600 MHz인 C밴드 안테나를 사용하였고, 신호의 증폭을 위해 마이크로파 앰프를, 다편파 측정 및 분석을 위하여 스위치를 장착하였다. 레일의 총 길이는 5 m, 이동간격은 5 cm, 최대 관측 거리는 약 200 m이다. 변위 측정에 사용된 이동산란체는 trihedral corner reflector로서, 시스템 전방 약 160 m에 위치하며 시스템 방향으로 1 mm에서 40 mm 전진시켰다. 이동산란체의 실제 변위와 GB-SAR 시스템의 위상변화로 관측된 변위의 상관계수는 편파에 따라 0.9995에서 0.9996으로 나타났다. 마이크로파의 전파과정에서 거리와 습도에 따른 지연 효과를 고려하기 위하여 대기보정식을 구하였으며, 이를 이동산란체의 위상에 적용한 결과 상관계수는 0.9997에서 0.9999의 값을 나타냈고 40 mm 이동시 오차가 1 mm 이내를 나타냄으로서 대기보정을 통한 결과가 더 높은 정밀도를 나타냄을 확인하였다.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.583-590
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• 1997

The effects of Mn2O3 and Y2O3 additives on the microstructure and dielectric properties of Sr(Zr, Ti)O3 have been investigated. Powders with Sr(Zr1-xTix)O3(0$\leq$x$\leq$0.1) composition were prepared by the conventional solid state processing from commercial TiO2 and precipitation-processed ZrO2. The powders containing sintering additives of Mn2O3 and Y2O3 were compacted and then sintered at 1,55$0^{\circ}C$ for 4 h to get>97% relative density. Mn2O3 suppressed the grain growth and Y2O3 enhanced the density of sintered body. The oxidation state of Mn ions were determined by a chemical wet method and EPR spectroscopy. Mn ions were present as Mn2+ and Mn4+ in SrZrO3, while as Mn3+ and Mn4+ in Ti-substituted Sr(Zr, Ti)O3. With the substitution of Ti, the lattice parameters of SrZrO3 decreased and its dielectric constant increased with remarkable decrease in Q value. The dielectric constant of Sr(Zr, Ti)O3 was in the range of 30 to 40, Q values 1,200~5,400 at 6 GHz and temperature coefficient of resonant frequency -67~100 ppm/K.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.3
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• pp.179-192
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• 2008

A multiphase compensation method with mismatch linearization technique, is presented and demonstrated in a $\Sigma-\Delta$ fractional-N frequency synthesizer. An on-chip delay-locked loop (DLL) and a proposed delay line structure are constructed to provide multiphase compensation on $\Sigma-\Delta$ quantizetion noise. In the delay line structure, dynamic element matching (DEM) techniques are employed for mismatch linearization. The proposed $\Sigma-\Delta$ fractional-N frequency synthesizer is fabricated in a $0.18-{\mu}m$ CMOS technology with 2.14-GHz output frequency and 4-Hz resolution. The die size is 0.92 mm$\times$1.15 mm, and it consumes 27.2 mW. In-band phase noise of -82 dBc/Hz at 10 kHz offset and out-of-band phase noise of -103 dBc/Hz at 1 MHz offset are measured with a loop bandwidth of 200 kHz. The settling time is shorter than $25{\mu}s$.