• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.436-444
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• 2016

The primary windings of the main transformer for rolling stock have several natural frequencies that can occur internal resonance with transient voltages induced on a high voltage feeding line. Factory testing is limited in its ability to determine whether or not transient voltage with various shape and duration can be excitable. This study presents the design of a high voltage windings model and simulation and analysis of the internal resonant characteristics in terms of the initial voltage distribution and voltage-frequency relationship using the electromagnetic transients program (EMTP). Turn-based lumped-parameters are calculated using the geometry data of the transformer. And, sub-models, being grouped into the total number of layers, are composed using a ladder-network model and implemented by the library function of EMTP. Case studies are used to show the layer-based voltage-frequency relationship characteristics according to the frequency sweep and the voltage escalation and distribution aspects in time-domain simulation.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.8
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• pp.9-16
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• 2000

MOS transistors are fabricated and evaluated for RF IC applications such as mobile communication systems using 0.35m CMOS process. Characteristics of MOSFETs are analyzed at various channel length, width and bias conditions. From the analysis, cut-off frequency ($f_T$) is independent on channel width but maximum oscillation frequency ($f_{max}$) tends to derease as the channel width increases. As channel length increases, $f_T$ and fmax decrease. $f_T$ is 22GHz and fmax is 28GHz at its maximum value. High frequency noise performance is improved with larger channel width and smaller channel length at same bias conditions. NFmin at 2GHz is 0.45dB as a minimum value. From the evaluation, MOSFETs designed using 0.35m CMOS process demonstrated a full potential for the commercial RF ICs for mobile communication systems near 2GHz. And optimization methods of the CMOS transistors for RF applications are presented in this paper.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1591-1592
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• 2006

이동 및 정보통신 시스템이 소형화 및 고성능화됨에 따라 System OR Package (SOP) 기술의 연구개발이 주목을 받고 있다. 저가형 SOP를 위하여 가장 많은 연구가 다층인쇄회로 기판에 수동소자 및 전송선로를 내장시키는 것이다. 본 논문에서는, 8층 KB 기판에 Meander line과 Radial/T Stub 패턴을 Advanced Design System(ADS) simulation을 이용하여 설계 및 제작하고 분석함으로써 정확한 SOP 디자인 및 설계 방향을 제시하고자 한다. 설계변수-패턴의 length, width, spacing, 각도와 공정변수-1층/3층, 기판 재질(prepreg(PP)과 resin coated copper(RCC))을 두어 제작하여 그 특성을 비교하였다. Meander Line는 PP보다 RCC에서의 인덕턴스가 크고 높은 자가 공진주파수를 가졌고, 3층보다 1층에서의 인덕턴스가 안정적이었다. Radial/T Stub는 PP보다 RCC에서의 커패시턴스가 작으나, 높은 자가 공진 주파수로 커패시턴스가 안정적이었다. Meander Line은 RCC, 병렬 전송선로 간격-400um, 병렬 전송선로 길이-500um, 1층 설계 시, 인덕턴스-1.60nH, 자가 공진주파수-9.21GHz 특성이 가장 우수하고, Radial Stub는 RCC, $60^{\circ}$, 1층 설계 시, 커패시턴스-0.62pF, 자가 공진주파수-9.06GHz의 특성이 나타났고, T Stub는 RCC, Stub 길이-600um, Stub 너비-150um, 1층 설계 시, 커패시턴스 -0.38pF, 자가 공진주파수-10GHz이상으로 우수한 특성을 나타냈다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2330-2334
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• 2014

In this study, we confirmed the frequency characteristics of planar spiral inductor based on non-contact method AC coupling for wireless signal transmission. The dielectric constant variation of the substrate does not directly effect the inductance of device but effect the electrostatic capacity of device. Therefore, its change self-resonance frequency. The thickness increment of the substrate increase inductance but decrease self-resonance frequency. Because, the thickness decrement of the substrate make the inside electrostatic capacity increment.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.132-135
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• 2001

본 논문에서는 SAR를 저감시킬 수 있는 IMT-2000 단말기용 PIFA의 설계에 대한 내용을 다루었다. 안테나의 설계 파라미터에 따른 공진 특성을 분석하고, PIFA와 동일한 공진 주파수를 갖는 모노폴 안테나와 Side-mounted PIFA를 설계하여 공진 특성과 SAR를 비교\ulcorner분석하였다. 그 결과 중심주파수에서 PIFA의 대역폭은 213MHz로 Side-mounted PIFA보다 50MHz로 증가하였고, 모노폴 안테나와 비교시에는 87MHz정도 감소하였다. 또한, 1g 및 10g SAR 평균 첨두치는 PIFA가 0.9869, 0.453 으로 Side-mounted PIFA, 모노폴 안테나에 비해 각각 10.3 %, 50% 감소하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.12
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• pp.1044-1049
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• 2015

In this paper, isolation enhanced antenna using isolating resonator was proposed. Two loop type antennas were designed to operate at Wi-Fi band(2.4~2.5 GHz), in symmetry to the center, and are closely located to each other. In order to enhance isolation characteristics at Wi-Fi bands, isolating resonator was designed between the two loop type antennas. The proposed isolating resonator is a slot type antenna that enhances isolation with the control of the size, and by adjusting the value of capacitor($C_D$) the resonant frequency of the isolating resonator can easily be adjusted to enhance isolation characteristic at the target frequency.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.6
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• pp.77-82
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• 1999

대형 화물트럭의 차실 내에 높은 수준의 차바닥 진동을 수반한 높은 소음이 발생하였다. 측정 및 분석결과 문제의 진동 소음은 추진축의 회전 1차 및 2차 성분으로 나타났다. 진동 전달경로상의 구성계 및 구성요소들에 대해 모드해석과 실차 주행 모드 해석시험을 실시한 결과 드라이브라인 및 프레임의 공진주파수가 문제가 되는 소음진동 주파수와 거의 일치하였으며, 또한 캡의 실내음향 공진 모드가 문제되는 주파수에서 존재하였다. 실험결과에 따라 액슬과 액슬간의 축의 장착각도를 변경하여 가진력을 줄이고, 비틀림 동흡진기를 추진축에 장착하여 드라이브라인계 공진을 제어함으로써 문제의 시내진동소음을 현저히 개선하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.15-27
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• 2008

In this paper, an EBG(Electromagnetic BandGap) resonator antenna with a stripline type FSS(Frequency Selective Surface) superstrate for PCS-band base station antennas is proposed. The characteristics of resonant frequency and -3dB bandwidth of a unit cell of a superstrate are first analyzed by varing several design parameters such as a strip width and a unit cell width in order to design an EBG resonator antenna satisfying the required antenna gain and bandwidth for PCS-band base station antennas. Among various unit cell shapes, strip dipole and stripline are considered and their characteristics are compared. It was found that a resonant length of the EBG resonator antenna becomes smaller when the stripline shape is used and the control of the bandwidth is also much easier. By using the unit cell simulation results, planar and cylindrical EBG resonator antennas at PCS-band are designed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.997-1002
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• 2009

This Letter presents a wideband ENG(Epsilon Negative) ZOR(Zeroth-Order Resonant) antenna designed on a microstrip line. It has a mushroom structure and its size is only $7.65{\times}1.31{\times}2.37\;mm$(or $0.306{\times}0.053{\times}0.095\;{\lambda}_0$ at 12 GHz) owing to zeroth-order resonance. The design procedures with closed form solutions are provided using transmission line theory considering radiation loss. The measured antenna bandwidth is about 20.0 % at 9.2 GHz and antenna gain is 7.1 dBi despite the compact size.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.663-669
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• 2016

A terahertz asymmetric split-loop resonator (ASLR) was analyzed for use in high-sensitivity sensing applications. Its structural asymmetricity induces an asymmetric Fano resonance which has a high quality factor compared to the symmetric eigen-resonance. The variations of the resonant frequency, transmission coefficient, and quality factor of the ASLR in the eigen and Fano resonances are analyzed as a function of its structural asymmetricity. Also, the surface current densities on the ASLR in both resonances are calculated to analyze the main cause of the variations of its transmission characteristics. The surface current of the ASLR in the eigen resonance shows a dipole resonance, which increases the radiation loss and reduces the quality factor. On the other hand, the surface current of the ASLR in the Fano resonance shows a trapped or quadrupole mode which has a low radiation loss. Therefore, the ASLR operated in the Fano resonance has a high quality factor. Terahertz, high-performance filters and high sensitivity sensors can be developed based on our analysis results of the ASLR having a high quality factor. These high-performance devices based on terahertz metamaterials could increase the adoption of terahertz industrial applications.