• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.12
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• pp.2241-2248
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• 2017

The coaxial line impedance transformer that performs impedance conversion using the coupling of two or more coaxial lines of the same length is often used for impedance matching in the low frequency region due to many advantages. This paper measures the phase and magnitude characteristics of each coaxial line in a 4:1 coaxial line impedance transformer using two 100mm coaxial lines. This experiment shows that it is more effective to make the length of the auxiliary coaxial line shorter than the main coaxial line by about 5 mm in order to realize a low loss impedance transformer. In addition, it measures the transmission characteristics by directly connecting a 4:1 impedance transformer and a 1:4 impedance transformer. This experiment shows that it is effective to connect a 1pF capacitor between the ground and the outer conductor input point of the main coaxial line in order to increase the operating frequency range.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.1056-1064
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• 2010

This paper presents the approximate analysis method for the symmetric transmission line crossing the aperture in an backplane. The method of moments is used to determine the aperture impedance for the construction of the equivalent transmission line that the aperture impedance apply to the transmission line as the shunt impedance. As the results, the insertion loss increases at the specific frequency range for the impedance matching. In the case of the mismatching, we are confirmed to the insertion gain at the specific frequency. Also the horizontal length of the aperture affects to the transmission line better than vertical length. The measurement of the insertion loss is performed to verify the theoretical analysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.8
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• pp.730-739
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• 2015

In this paper, a wideband circular polarizer operating in the frequency range of 6~18 GHz is designed and fabricated using a multilayer structure with meanderlines. A T matrix expression for the unit structure, which consists of meanderline, dielectric substrate and spacer, was derived using the boundary value solution. A proposed meanderline structure was modeled as an array of unit meanderline cell in order to apply the waveguide model with PEC and PMC boundary conditions. The calculation procedures to obtain an equivalent susceptance of the unit meanderline cell using HFSS was also suggested. Using a hybrid method, which combines the T matrix with the HFSS results, and cut-and-try method, a wideband circular polarizer with low insertion loss and good AR performance was designed. The fabricated polarizer has the return loss less than -10 dB within 92 % bandwidth, the average insertion loss less than -0.24 dB, and the average AR below 2.6 dB for full 3:1 bandwidth.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.503-504
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• 2011

주파수가 다른 계통을 연계하거나, 장거리 선로 운전시 손실이 낮은 HVDC 송전은 환경문제로 인한 민원으로 새로운 선로건설을 위한 부지확보가 전 세계적으로 어려운 실정이다. 이 문제를 해결할 수 있는 방안으로 기존의 AC선로에 DC를 적용하여 동일철탑에 AC와 DC 선로를 같이 설치하는 하이브리드(Hybird) 선로가 제시되었다. 그러나 AC와 DC가 공존한 상태에서의 전기환경기준이 제시되지 못하고 있는 실정이다. 따라서 본 논문에서는 국내에서 운용중인 345kV 2회선 철탑에 DC선로를 적용한 하이브리드 선로의 축소모델을 제작하였고, DC선로의 도체 구성별 하이브리드 선로의 이온류 특성을 시험하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.565-573
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• 2000

In this paper, a interdigital microstrip bandpass filter is designed. A interdigital microstrip bandpass filter has many advantages such as insertion return loss, lower return loss, higher frequency selectivity and smaller in size in comparison with the conventional coupled line filter. A interdigital microstrip bandpass filter consists of quasi TEM-mode strip line resonators between parallel ground plant. Each resonator element is a quarter wavelength long of the center frequency and is short circuited at one end and open circuited at the other end. In the filter design, Ensemble software is used. Experimental results show that the bandwidth of interdigital microstrip bandpass filter is 2.52GHz, insertion loss is -1.8dB and return loss is -17.0dB at 11.20Hz.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.67-71
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• 2008

We report the waveguide to microstrip transition using probe structure for Ka-band transceiver. The waveguide to microstrip transition is composed of probe, inductive line, ${\lambda}/4$ impedance transformer, and $50{\Omega}$ microstrip line. For design of the transition, we optimized the characteristic impedances and the lengths of the component parts. The fabricated transition exhibits an insertion loss of 1.3 dB and the input/output return losses of below 14 dB between 30 and 40 GHz. The insertion loss of each transition is about $0.5{\sim}0.6dB$, considering the losses in the microstrip line and input/output waveguides.

• Proceedings of the KIEE Conference
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• summer
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• pp.227-229
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• 2004

시대가 변화 하면서 선로손실 및 전압강하문제에 많은 관심을 가지게 되면서, 현재 사용중인 선로 정수값에 대한 고찰을 필요로 하게 되었다. 본 논문에서는 배전선로정수에 대한 현황 및 근거를 확인하고, 또한, 선종별로 장주의 배치에 따른 인덕턴스값 및 온도변화에 따른 교류저항값등에 대한 분석 내용을 소개하기로 한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.10a
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• pp.577-586
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• 1998

본 논문에서는 RLCG 전송선로를 가진 Chua 회로에서의 카오스 동기화 방법에 대하여 연구하였다. 두 개의 동일한 Chua 회로에 전송 선로를 두어 RLCG 전송로를 구성한 후 송신부와 전송선로 사이는 구동-결합 동기 이론을, 전송선로와 수신부 사이는 결합 동기 이론을 적용한 동기화 방법을 제시하였으며, RLCG 전송 선로를 가진 Chua 회로의 카오스 동기화는 전송 선로의 L과 C 영향에 의한 시간 지연이 있는 일반화된 동기화가 이루어짐을 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.286-291
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• 2011

Directional couplers are widely used in RF and microwave applications to distribute or monitor signals. This paper presented a new structure of microstrip branch line directional coupler with coupled lines. The loose couplings of microstrip branch line directional couplers are impractical for the high characteristic impedance values required for the shunt branches. To overcome this limitation, the parallel coupled lines with the shorts were used for the high characteristic impedance. The results of the simulations and measurements were presented for the proposed branch line directional coupler. Measurement of the 10 dB branch line directional coupler shows that the return loss is higher than 30 dB over 10 % bandwidth and the isolation is 35 dB or better over 8 % bandwidth.

• KEPCO Journal on Electric Power and Energy
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• v.4 no.1
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• pp.9-12
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• 2018

The use of underground transmission power lines is expanding for the beauty and convenience of the near city. However, there is a lack of research on the losses from underground transmission power lines, especially those that support three-phase cables operating 24 hours a day. Since the supporting the cable is made of a material having a conductivity and a magnetic permeability, an eddy current and a hysteresis loss are generated due to a magnetic field caused by a current flowing in the cable. Losses occurring in this case adversely affect the power energy transfer efficiency, so research on loss is necessary. Therefore, in this paper, we analyzed the eddy currents and hysteresis losses that occur in a supporting a cable through three - dimensional finite element analysis.