• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.5 s.122
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• pp.427-436
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• 2007

The catenary of a high-speed electrical train is modeled by the finite elements with the upper suspension wire, lower contact wire, and droppers, and the dynamic contact between the catenary and the pantograph is numerically analyzed by solving the whole equations of motion of the pantograph and the catenary system subjected to the contact condition. For the stability of the numerical solution, with the cubic spline interpolation of the catenary displacement, the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Through the various numerical examples, it is shown that the dropper positions as well as the static deflection are crucial to determine the contact and separation of the pantograph of a high-speed train.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.2
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• pp.182-191
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• 1988

A log periodic microstrip array antenna using direct coupling feeder is designed at the frequency 7.2-12.4GHz. Transmission line analysis method was used for the design of each antenna element in consideration of the effects of dielectric and conductor loss and the discontinuity, also the optimized feeding points were obtained for the impedance matching between a main transmission line and each antenna element. It is shown that the measured VSWR was less that 2.4 at the frequency 7.2-12.4GHz, and 53% bandwidth was achived.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1273-1274
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• 2015

본 논문에서는 주파수 무관(frequency independence) 특성을 갖는 자기상보 구조(self-complementary structure)로 된 안테나의 급전선로(feed line)로 사용할 수 있는 초광대역 발룬(ultra-wideband balun)을 제안하였다. 발룬을 설계하기 위해 클로펜스타인 테이퍼(Klopfenstein taper)를 사용하여 임피던스 프로파일(impedance profile)을 구하고 이를 평행 스트립 선로(parallel strip line) 구조로 구현하기 위해 등각사상방법(conformal mapping method)을 이용했다. 설계한 발룬을 직접 제작하여 측정한 결과, 대역폭은 반사손실 -10 dB를 기준으로 할 때 0.45~10.53 GHz까지 10.08 GHz로 나타나, UHF(ultra high frequency) 통신대역에서 UWB(ultra-wideband) 통신대역에 이르기까지 매우 넓은 주파수 범위에서 자기상보형 안테나의 입력 임피던스 $188{\Omega}$을 $50{\Omega}$의 특성 임피던스에 정합시킬 수 있음을 확인하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.937-942
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• 2007

A new, systematic, simplified design procedure for quasi-Yagi antennas is presented. The design is based on the simple impedance matching among antenna components: i.e., transition, feed, and antenna. This new antenna design is possible due to the newly developed ultra-wideband transition. As design examples, wideband quasi-Yagi antennas are successfully designed and implemented in Ku- and Ka-bands with frequency bandwidths of 53.2% and 29.1%, and antenna gains of $4{\sim}5 dBi$ and $ 5{\sim}5.6 dBi$, respectively. The design method can be applied to other balanced antennas and their arrays.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.10
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• pp.1086-1095
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• 2008

In this paper, we designed and fabricated the trapezoidal antenna using the CPWG structure for Wibro and WLAN communications. This antenna has broadband characteristics using the basic trapezoidal antenna, and an H-shaped parasitic patch is making an expansion of resonance bandwidth and bringing stability of impedance matching. Especially, CPWG structure is combined two kinds of the structure which of a monopole antenna and a coplanar waveguide antenna. They make up for the weak point of the CPW which is variation of impedance matching according to varying the gap or size of the feed line and the ground. The designed antenna has occurred resonances of which the band of 2.2 GHz to 4.6 GHz(70.5 %) below the return loss of -10 dB($VSWR{\leq}2$) obtained in measurement, and it has an omnidirectional radiation pattern of H-plane. In addition, the changes of impedance matching appear slightly caused by the effects of the ground plane and the feed line.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.973-984
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• 1999

This paper presents a method of moments with the transmission line theory to analyze the sleeve dipole array antennas and analyses characteristics of that. There were several considerations for analysis of the method of moments. First, the method of moments were applied at both of the sleeve dipole elements and the coaxial line because the current flows on both of them. Second, the feed voltages of each sleeve dipole element were obtained by using a transmission line theory because the feeding structure is fed by coaxial line in series. Third, the series reactance between the coaxial line and the open side of the sleeve was considered as impedance loading on the antenna. The radiation patterns and current distributions from the numerical results were considered as variation of the feed distances and frequencies. To verify the validity of our method, 4 elements sleeve dipole array antennas with 1 λg distance were fabricated and measured, and then the measured radiation patterns were compared with the numerical results. The measured results were confirmed a good agreement with the numerical results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.176-179
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• 2006

As spurious emission strength is normally measured at the antenna feeder, It is required that the measurement method on passive Intermodulation occurred on the latter part of antenna feeder be made. through the tests and the analyses of passive Intermodulation between radiostations of adjacent frequency bands, the possibility of occurrence of passive Intermodulation was testified in this study. The purpose of this study is to propose the measurement method of spurious emission strength in order to prevent the bad effect by passive Intermodulation.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1583-1584
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• 2015

최근 철도차량의 고속화와 전력회생을 하는 전기차로 인하여 부하전류와 고장전류 간의 큰 차이가 없으므로 이를 구분할 수 있는 고성능 보호시스템의 중요성이 날로 증대되고 있다. 본 논문은 실계통에서의 전차선로 임피던스를 이용하여 AT급전시스템을 모델링하였으며 변전소와 보조급전구분소사이 단락사고의 과도특성을 분석하였다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.272-273
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• 2015

This paper analyze scenario of feeder wire fault that occurs in the AC feeding system considering train position. The fault location of AC feeding system is calculated by measuring impedance. However, in this way, estimation error can be occurred because of tie connection, boosting current, etc. Therefore, it's hard to find fault location, so that it is required to detailed circuit analysis according to fault location. We analyze the short circuit impedance values with respect to feeder wire fault according to a train position. In this paper, PSCAD is used for modeling and analysis of AC railway feeding system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.1 no.2
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• pp.131-136
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• 1997

In this paper, the input impedance of coaxial fed rectangular microstrip patch antenna located inside rectangular waveguide is calculated by using the cavity model and the mode excited in the waveguide by the patch antenna. The return loss and efficiency of the patch antennas as a function of feed position in. free space and in waveguide are calculated and compared. The maximum efficiency of the antennas in waveguide and in free space are obtained at different feed position.