• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.1
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• pp.116-119
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• 2010

In this work, we presented the characterization of 3 dB branch type directional couplers by using High-Tc superconducting thin films. To do this, we deposited YBCO superconducting thin films on MgO substrates by using rf-magnetron sputtering techniques. The designed center frequency was 408 MHz and the designed passband was 20 MHz. Also we designed 3 dB Power difference and $90^{\circ}$ of phase difference between port 3 and port 4. The even and odd mode analysis were used to characterize our directional couplers and em Sonnet (full wave analysis program) was utilized to the optimum design. We reported experimental results, including a center frequency, passband, half power characteristics and phase differences. We confirmed that experimental results were in good agreements with characterization by using full wave analysis program.

• ETRI Journal
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• v.27 no.6
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• pp.788-797
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• 2005

This paper describes the design and realization of an extra high frequency band $8{\times}8$ microstrip Butler matrix. Operation at 36 GHz is achieved with a frequency bandwidth exceeding 400 MHz. The circuit is implemented on a bi-layer microstrip structure using conventional manufacturing processes. This planar implementation of a Butler matrix is a key component of a switched beam smart antenna with printed antenna elements integrated on-board. Conception details, simulation results, and measurements are also given for the components (hybrid couplers, cross-couplers, and vertical inter-connections) used to implement the matrix.

• ETRI Journal
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• v.27 no.6
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• pp.697-707
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• 2005

This paper proposes a new design of directional couplers with high directivity for personal communication services (PCS) and International Mobile Telecommunications-2000 (IMT-2000). The directional coupler is used to check and verify the power, frequency, and antenna reflection of a signal at transmission stations for mobile communications. The performance requirements of directional couplers are a strong coupling to reduce the effect on the transmitted power and high directivity to suppress the interference of the reflected signals and reduce the errors in communication. So far, various architectures have been proposed to gain high directivity, and there have been many studies used to obtain a strong coupling. However, conventional architectures for high directivity and strong coupling have a directivity of only about 20 dB, and there have been difficulties to achieve the higher directivity of 30 dB suitable for PCS and IMT-2000. This paper proposes a new architecture of directional couplers based on a grounding composed of strip lines, and compares the test results of this directional coupler with conventional ones. The results show that the proposed directional coupler has a directivity of more than 30 dB and is adequate for PCS and IMT-2000.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1996.09a
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• pp.89-94
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• 1996

In this paper A methode for design of hybrid-ring couplers having sections of lenth λ/n is proposed. Assuming only one - axis symmitry and isolation of output arms general expressions for the scattering parameters are obtained. The new design method using λ/n sections for 3 dB couplers is derived, . The calculated frequency reponse of the new design has been compared with that of conventional ones, . A new design using λ/5 section and having an overall length 13λ/10 is found to be superior to the 7λ/6 design is expected to have a low insertion loss by virtue of its shorter length.

• Journal of the Korean Ceramic Society
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• v.36 no.6
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• pp.583-589
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• 1999

In the fabrication of ceramic chip couples for high frequency application such as the mobile communication equipment the formation of electrode lines and Ag diffusion were investigated with heat treatment conditions for removing organic binders. The deformation and densification of the electrode line greatly depended on the binder burnout process due to the overlapped temperature zone near 400$^{\circ}C$ of the binder dissociation and the solid phase sintering of the silver electrode. Ag ions were diffused into the glass ceramic substrate. The Ag diffusion was led by the glassy phase containing Pb ions rather than by the crystalline phase containing Ca ions. The fact suggests that the Ag diffusion could be controlled by managing the composition of the glass ceramic substrate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.921-928
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• 2003

This paper propose a new design of directional couplers with the high directivity. The directional coupler is used to check and verify the power, frequency and antenna reflection of a signal at transmission station for the mobile communications. The performance index of the directional coupler is to which the coupling is strong to reduce the effect on the transmitted power and the directivity is high to suppress the interference of the reflected signals and reduce the nor in the communication. Then, the architectures to gain the high directivity and the studies to get the strong coupling have been proposed However, the conventional architectures lot the high directivity and strong coupling have the directivity by about 20㏈ and the difficulty to achieve the higher directivity than 40㏈ suitable for IMT-2000 [1]. This paper proposes an architecture of the directional coupler which is based on the grounding composed of the strip lines and the comparison results with the conventional directional couplers. The comparison results show that the proposed directional coupler has the directivity more than 40 ㏈ and is adequate for the 2.05GHz IMT-2000

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.6
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• pp.409-416
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• 2005

For broadband high-data-rate power line communication with the allocated frequency bandwidth from 2 to 30 MHz on medium voltage (MV) distribution power lines, a signal coupling unit is developed. The coupling unit is composed of a coupling capacitor for coupling communication signal, a drain coil, and an impedance matching part. The coupling capacitor made of ceramic capacitor is designed for transmission property of better than 1 dB in the frequency range. The drain coil is used for preventing low frequency high voltage from junction of medium voltage power line in case that a coupling capacitor is not working properly any more. Also, using ferrite core, a novel broadband impedance matching transformer is developed. A complete coupling unit with a coupling capacitor, a drain coil, and a matching transformer is housed by polymer for good isolation and distinguishing from high voltage electric facilities. Each is fabricated and its frequency behavior is tested. Finally, complete signal couplers are equipped in a MV PLC test bed and their performance are measured. The measurement shows that the coupling capacitor works excellently.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.12
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• pp.1618-1623
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• 2019

In this paper, inductive couplers realizing broadband powerline communication (PLC) are fabricated using Fe-based nanocrystalline alloy and their performance is analyzed. As a result of the field tests using the distribution automation system (DAS), the couplers achieve comparatively excellent data communication in the principal frequency band of broadband PLC although there is a difference in communication rate depending on the presence or absence of a branch. In addition, it has been confirmed that the communication speed is maintained for a real-time transmission even in a high current environment although there is a difference in the transmission rate depending on the distance. Hence, it is considered that the inductive couplers can be used as a core device to realize the intelligent power network by exploiting them for the monitoring and remote controlling of the power plant equipments for the DAS located in the inaccessible areas.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1776-1778
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• 2003

Partial Discharge(PD) pulses propagate in gas insulated substation(GIS) with rise time shorter than one nanosecond. Therefore, Ultra high frequency(UHF) couplers which have ultra wide band(UWB) characteristics from hundreds of MHz to several GHz are desirable for the detection of the PB pulses in GIS. In this paper, the authors proposed a log-periodic antenna for GIS PD detection. Various parameters of the coupler such as frequency bandwidth, coupler gain, radiation pattern, coupler geometry were considered through the simulations and the experiments together.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.2
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• pp.69-75
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• 2005

In order to improve the reliability of high voltage rotating machines and mold transformers, it is necessary to understand the breakdown mechanism and life assessment of the high voltage winding parts. Especially the on-line PD test provides the ability to monitor effects, such as slot discharge, internal discharge, and end-winding discharge without interrupting the electrical machines, this method has been proven the major testing technology. Capacitive couplers have been the most widely used sensors for the on-line partial discharge detection in rotating machines nowadays. This paper deals with the electrical characteristics and long-term reliability of a ceramic coupler(CC), which can be easily mounted into high voltage input terminal part, has been developed and tested to continuously measure PD activity during operating condition. This paper presents electrical characteristics (dielectric loss angle, capacitance, PD inception level, breakdown voltage, and frequency response bandwidth) and long-term life test result of the developed 6.6 kV class on-line ceramic coupling sensor. It was found that this sensor had good electrical characteristics to detect PD activity during the operating condition with its detection frequency band is between several and several tens MHz. Also, the voltage life of the 6.6kV class ceramic coupler was calculated over 60 years.