• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.434-442
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• 2003

Taking advantage of the probability function, we have analyzed the localization phenomenon of the solution of a propagating function under the condition that the propagation constants are randomly distributed. For example, we have investigated the localization phenomenon of the voltage wave for a transmission line in which the characteristic impedance is randomly distributed. We have confirmed that the localized solution is in existence on the random lossless transmission line. Even in the case that the voltage wave is impulsively excited by the current source, the voltage wave is localized. Because the light wave is seriously affected at the localized position in the lossy transmission line, we have determined that the light wave localization phenomena are generated by multi-reflection.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.6 s.121
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• pp.680-688
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• 2007

Time domain closed-form analytical solutions to the coupled telegrapher's equations for the voltage and current on a lossless multiconductor transmission line are presented. The resulting expressions are obtained in the form of exact time domain propagators operating on the line voltage and current. Time domain numerical methods are developed and examples showing exceptionally accurate results are obtained for uniform and nonuniform; symmetric and asymmetric strip lines.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.328-332
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• 2000

본 논문에서는 기생 패치 구조와 적층 구조의 광대역 마이크로스트립 안테나에 평행 결합 선로 형태의 광대역 임피던스 정합 회로를 결합하여 쉽게 추가적인 임피던스 대역폭 개선을 얻을 수 있음을 제안하였다. 평행 결합 선로 형태의 광대역 임피던스 정합 회로 설계를 위하여 분포 회로 방식의 반복적인 방법을 제시하였고. 설계\ulcorner제작 결과 기생 패치 구조와 적층 구조에서 각각 56.23%와 16.45%의 추가적인 임피던스 대역폭 개선을 이룰 수 있었다. 그리고 방사 패턴과 측정된 이득을 보면 평행 결합 선로의 결합으로 인한 방사 패턴에서의 큰 변화는 보이지 않았고, 이득에서는 평행 결합 선로 부분의 커플링 손실로 인해 최대 이득이 약 1 dB 정도 감소하는 것을 확인할 수 있었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.761-770
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• 2008

Impedance or admittance inverter is a conceptual 2-port device frequently used in microwave filter design. In this paper, the equivalent circuit using inverter for general loss less 2-port circuit is presented. Our equivalent circuit can be directly and easily represented with z- or y-parameters compared with the conventional methods. Based on the representation, the derived results for various coupled lines such as parallel coupled line and anti-parallel coupled lines are compared ours. In addition, the results of other workers for improvement of the distortion in frequency response of microstrip coupled line filter are derived using our representation and compared. The proposed equivalent circuit shows the difference with conventional equivalent circuit so the conventional design method can not be applied to parallel coupled line filter with our representation. So in this paper the novel design method is proposed and we showed the method yields more accurate design results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.3
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• pp.231-240
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• 2005

Recently, the needs and concerns for the power loss are increasing according to the energy conservation at the level of the national policies and power utilities's business strategies. Especially, the issue of the power loss is the main factor for the determining the electric pricing rates in the circumstances of the deregulation of electrical industry. However, because of the lacking of management for power loss load factors (LLF) it is difficult to make a calculation for the power loss and to make a decision for the electric rates. And loss factor (k-factor) in korea, which is a most important factor for calculation of the distribution power loss, has been used as a fixed value of 0.32 since the fiscal year 1973, There(ore, this study presents the statistical calculation methods of the loss factors classified by load types and seasons by using the practical data of 65 primary feeders which are selected by proper procedures. Based on the above the algorithms and methods, the optimal method of the distribution loss management classified by facilities such as primary feeders, distribution transformers and secondary feeders is presented. The simulation results show the effectiveness and usefulness of the proposed methods.

• Journal of the Korean Society for Railway
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• v.15 no.4
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• pp.357-363
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• 2012

This paper presents a new operation method for the single phase PWM(Pulse Width Modulation) converter train. Recently, the trains adopting the PWM converter have become the majority in the electric locomotives since there are distinct advantages over the predecessors, which can be operated at near unity power factor. However, a slight modification of the control scheme makes this kind of vehicles run in the region of leading power factor. Although this feature seems to be of no significant use by itself, the leading phase operation can improve the voltage profile and the line loss of the feeding systems is decreased by compensating the reactive power loss along the line when it considered together with the feeding systems. This method is even more economical and efficient comparing with the installation of SVC that is mainly used for this purpose since the train can become a movable compensator. With the conditions and some essential formula for the leading phase operation, a new power factor control algorithm has been proposed to implement this scheme. The results of simulation through SIMULINK model show that the proposed method is suitable enough for practical use.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.9
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• pp.1729-1733
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• 2007

In this paper, we have carried out some tests for analyzing the effects of optical fiber characteristics and piping structures in designing a Customer Cabling System with optical fibers. In this tests, the loss characteristics due to the number of curvatures and the radius of curvature with bending to establish an optical fiber have analyzed particularly. We can confirm that the test results satisfy the current technical regulations in both cases of the number of curvatures and the radius of curvatures. Also, in particular, since there is no loss in an optical cable under the current radius of curvature, that is 30mm, the radius criteria of curvature needs to be revised. These tests results will be so useful to revise and establish a customer cabling system for FTTH.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.2
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• pp.95-103
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• 2019

In this paper, we present a microstrip-to-substrate integrated waveguide(SIW) transition and microstrip-to-hollow SIW(HSIW) transition for Ku-band satellite communication systems. For the complete utilization of the HSIW, a structure filled with air instead of a dielectric material, a microstrip-to-HSIW transition is designed, fabricated, and compared with a microstrip-to-SIW transition. A back-to-back microstrip-to-SIW transition is measured in the range 12~18 GHz; it exhibits a return loss ${\geq}20dB$ and an insertion loss of $1.5{\pm}0.2dB$. In contrast, a back-to-back microstrip-to-HSIW transition exhibits a return loss of at least 15 dB and an insertion loss of $0.55{\pm}0.2dB$ in the same frequency range.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.5
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• pp.444-449
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• 2009

This paper presents the design of a dual band branch line hybrid coupler(BLHC) with different power division ratios at two bands. In the proposed design, transmission lines of the BLHC are transformed to $\pi$-type equivalent circuits which represent different impedances and $\lambda/4$ electrical length at two frequency bands. In order to verify the proposed method, a dual band coupler with different power division ratios is designed for 0.9 GHz and 2 GHz applications. The desired power division ratios are 1:1 and 1:3 at the two operating frequency bands. The measured results show excellent performance with an insertion loss of less than 0.33 dB, a return loss of less than -18.07 dB, and good isolation characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.307-314
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• 2010

In this paper, a novel ultra-wideband microstrip-to-suspended stripline(SSL) transition is proposed, and SSL filters with low-loss and high selectivity have been realized using this transition. Since the proposed transition has low-loss and wide bandwidth characteristic, the design procedure of SSL filters become simplified. Additionally, the designed filters do not require extra time-consuming tuning. As design examples, SSL low-pass and high-pass filters have been implemented, and a implemented bandpass filter with connection of the low and high-pass filters performs 2.3~10.5 GHz bandwidth with less than 1.2 dB insertion loss and high selectivity.