• Journal of the Korean Society for Railway
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• v.11 no.6
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• pp.575-580
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• 2008

When constructing a high-speed railroad, the reduction of the distance between track centers and the width of track bed will save the construction cost. However the shortening the distance between track centers may cause the stability problems due to higher wind pressure. Therefore the extensive technical review and aerodynamical study should be performed to determine the adequate distance between track centers. In this study, the impact that the increase in wind pressure due to the change of aerodynamic phenomena with the change of the distance between track centers may have on two trains passing by each other was predicted, and the stability of train operation was analyzed in order to review the distance between track centers suitable to Honam HSR trains. And we estimated the aerodynamical effects by the results of the field test.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.487-491
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• 2007

When constructing a high-speed railroad, the reduction of the distance between track centers and the width of track bed will save the construction cost. However the shortening the distance between track centers may cause the stability problems due to higher wind pressure. Therefore the extensive technical review and aerodynamical study should be performed to determine the adequate distance between track centers. In this study, the impact that the increase in wind pressure due to the change of aerodynamic phenomena with the change of the distance between track centers may have on two trains passing by each other was predicted, and the stability of train operation was analyzed in order to review the distance between track centers suitable to Honam HSR trains. And we estimated the aerodynamical effects by the results of the real train experiments.

• Journal of the Korean Society for Railway
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• v.12 no.6
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• pp.961-966
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• 2009

When constructing a high-speed railroad, the reduction of the distance between track centers and the width of track bed will save the construction cost. However the shortening the distance between track centers may cause the stability problems due to higher wind pressure. Therefore the extensive technical review and aerodynamical study should be performed to determine the adequate distance between track centers. In this study, the impact that the increase in wind pressure due to the change of aerodynamic phenomena with the change of the distance between track centers may have on two trains passing by each other was predicted, and the stability of train operation was analyzed in order to review the distance between track centers suitable to Honam HSR trains. We conducted the parametric study of the effects of train wind on the running stability.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.6
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• pp.598-604
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• 2011

A method of miniaturizing branch line coupler with connected coupled lines is presented. The quarter-wavelength transmission lines in the typical microstrip branch line coupler are replaced with the connected coupled lines with same characteristics of ones for compact size. The connected coupled line is analyzed by T-equivalent circuit and Z parameters based on the even-odd mode analysis. The proposed branch line couplers with connected coupled line are designed and fabricated on FR4 substrate at 2.4 GHz. The measured results show good agreement with theoretical prediction. And the experimental results show that the size of coupler is 37 precent smaller than conventional coupler. This minimized coupler is suitable for Butler Matrix as feeder for mobile communication beam forming antenna.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.556-558
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• 2001

초고속인터넷서비스란 이름으로 국내에 인터넷의 붐을 촉진시킨 ADSL(Asymmetric Digital Subscriber Line) 서비스가 가입자망의 한 형태인 FTTC(Fiber To The Curb)를 이용하여 밀집 주거지역(주로 아파트)을 중심으로 급격히 확산하면서 일부에서는 ADSL의 특성상 건물의 구내통신선로설비 부분이 서비스의 품질을 저하시킬 수 있다는 우려가 대두되었다. 본 논문에서는 아파트의 구내통신선로설비가 어떤 상황인지를 점검해보고 서비스 품질에 영향을 미칠 수 있는 요소가 무엇인지, 영향을 미친다면 어느 정도인지, 그리고 양질의 서비스를 제공하기 위해서 구내통신선로설비 차원에서 사전에 해소되어야 할 요소가 무엇인지를 살펴본다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.3
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• pp.298-306
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• 2014

The railway signalling system for safe train operation regulates the train speed to ensure the safety distance between consecutive trains by using wayside facilities such as track circuits and interlocking systems. In addition, this signalling system controls the trackside equipment such as a railway point along the train line. This ground-equipment-based train control systems require high CAPEX and OPEX. To deal with these problems, the train control system using the on-board controller has been recently proposed and its related technologies have been widely studied. The on-board-controller-based train control system is that the on-board controller can directly control the trackside equipment on the train line. In addition, if this system is used, the wayside facilities can be simplified, and as a result, the efficient and cost-effective train control system can be realized. To this end, we have developed the prototypes of the on-board controller and wayside object control units which control the point and crossing gate and performed the integrated operation simulation in a testbed. In this paper, before the field test of the on-board-controller-based train control system, we perform the preliminary field trial including the installation test, wireless access test, interface test with other on-board devices, and normal operation test.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.3
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• pp.445-450
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• 2017

In this paper, the directional coupler with half-power division is designed and fabricated by using the vertical coupling structure based on the CPW transmission-line. Even-mode and odd-mode of the vertical coupling structure can be analyzed by the conventional CPW-line and the CBCPW-line, respectively, with half thickness of the substrate. The directional coupler is designed by using the tefron substrate with the dielectric constant of 2.55 and the thickness of 0.76mm. Manufactured directional coupler has the center frequency of 2.45 GHz and the bandwidth of 66.1%. Also, the return loss and isolation are 19.52dB and 19.47dB, respectively, at the center frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4A
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• pp.232-237
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• 2003

We present the derivation of the loci of the reflection coefficient of a loaded transmission line on the Smith chart as the length of the transmission line is varied. The results show that the loci constitute a circle when the characteristic impedance of the transmission line differs from the normalizing one, whose center and radius are determined by the impedances of the load and the transmission line. The results can be used in the matching circuit design using microstriplines when line width and length should be compromised.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.5
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• pp.795-801
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• 2001

A method of miniaturizing branch line coupler is presented. The method utilizes the microstrip line with overlay(or superstrate). The frequency dependent characteristics, dispersion and characteristic impedance, of this line are obtained by Immitance method in spectral domain and Method of Line. The relevant spectral domain Green's function is given and used to obtain numerical results. The branch line couplers with overlays are designed and fabricated at 2 GHz. The experimental results show that the size of coupler with overlay(${epsilon}_r$=10.2) is 31.4 precent smaller than conventional coupler. This minimized coupler is suitable for Butler Matrix as feeder for mobile communication beam forming antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.7
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• pp.664-672
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• 2009

In this paper we propose an on-glass antenna which consists of conducting dual center striplines and multi-loaded striplines. Multi-loaded striplines and dual center lines were employed for achieving a broad matching bandwidth and improving a vertical radiation gain, respectively. The detail design parameters were determined using the Pareto genetic algorithm with an full wave EM simulator. The optimized design was built and installed on a commercial vehicle, and the antenna performances such as the return loss and the radiation gain were measured in a semi-anechoic chamber. The measurement results showed the matching bandwidth($S_{11}$<-3 dB) of about 49 % in the T-DMB frequency band, the vertical gain of about -3 dBi along the bore-sight direction, and the average gain of about -10 dBi along the azimuth direction.