• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.33-35
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• 2003

There are three types that geometrical arrangement of the pulse tube and regenerator - in line type, U type, and coaxial type. The most compact and convenient one practical applications is the coaxial type. It can replace Stirling cryocooler without any change to the Dewar or the connection to the cooled devices. To investigate effects of the inertance tube, we perform experiments with varying inertance tube inner diameter and length. The experimental results show that optimum inertance tube inner diameter and length are 1.3mm, 1900mm respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.187-190
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• 1998

In this paper a probe for the' measurement of dielectric properties of dielectric sheet materials is designed and implemented as a coaxial air line type. Using the broadband impedance method with this measurement probe the dielectric constant and loss tangent of the glass-epoxy and teflon are determined in the frequency range of 0.1 - l.O[GHz] with the temperature variation from $25[^{\circ}C]$ up to $65[^{\circ}C]$. A measured relative dielectric constant of the glass-epoxy is 4.42 and a loss tangents is 0.019 relatively, and the relative dielectric constants of teflon is 2.17 and a loss tangents is 0.002 relatively

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.11
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• pp.874-879
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• 1991

The effect of air gap between specimen and jig on the material constant (permittivity, permeability) and attenuation characteristics of electromagnetic wave absorbers in the coaxial line method was investigated. The presence of a air gap made both permittivity and permeability measured lower than true value, and the tendency was greater in the case of permittivity. An inner gap compared to an outer gop was found to yield a larger difference between measured and true values. The effect of air gap was measured for a Ni0.3Zn0.7Fe2O4, with the gap eliminated by metallizing with Ag-paste. The measured characteristics were in good agreement with corrected values by calculation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.624-627
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• 2000

The shielding effectiveness of materials is determined by measuring the ratio of the incident electromagnetic power which passes through the material under test. To measure the shielding effectiveness materials made by conductive polymer, the flanged coaxial transmission-line holder based in ASTM D4935-89, was fabricated. This apparatus has dynamic range between 95dB and 120dB in frequency range of 50Mhz-2Ghz. Furthermore, this system can be utilized to measure the shielding effectiveness of materials produced by conductive polymer and can be adapted for shielding materials design.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.107-113
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• 2008

In 22.9[kV]-y distribution systems, underground cables are provided with multiple-point ground in which each coaxial-neutral line of the distribution cable lines(A, B, C phases) is 3-wire common grounded. In the underground cable distribution systems, circulating current flows in the coaxial-neutral lines and its magnitude amounts to about $40{\sim}50[%]$ load currents, even though loads are balanced. Power loss due to the circulating current consequently reaches to about 76[%] total losses occurred in all conductor lines. This power loss provokes additional temperature rise of the underground cable lines and finally results in 20[%] reduction of the current capacity of the cables. This paper presents a new ground method to overcome such a problem. The proposed method eliminates the circulating current flowing in the coaxial-neutral line effectively. Measurement results confirmed from the practical site-test show validity and effectiveness of this research.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.8
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• pp.19-26
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• 1999

umerical simulations are performed to estimate how strongly the manufacturing error of an open-ended coaxial probe affects its measured complex permittivity of a contacted medium. The reflection coefficients of several dielectric materials contacted with an open-ended coaxial probe are calculated by employing the FDTD method. And then those complex permittivities are reconstructed by applying the calculated reflection coefficients into a new imaginary transmission-line model, which reveals more physically meaningful than the conventional model. It is found that the reconstructed complex permittivities suffer from significant error in spite of a slight imperfection of open-ended coaxial probe.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.661-668
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• 2012

A coaxial-cable impedance transformer that can be used in high power and wideband frequency range is an arbitrary impedance transformation ratio by an additional coaxial cable. The coaxial-cable impedance transformer to be 50-${\Omega}$ to 25-${\Omega}$ impedance transformation ratio is easily operated an wideband power divider by connecting two 50-${\Omega}$ lines at 25-${\Omega}$ impedance point. This wideband power divider has a poor output matching characteristic and a poor isolation characteristic between two output ports. In this paper, it proposes a coaxial-cable power divider to be a good output matching and isolation characteristics as it uses the singly terminated filter design theory. The odd-mode operation characteristic of the suggested power divider to use singly terminated low pass filter coefficient due to matching order and ripple value is examined by ADS program. And, it fabricates and measures the operation characteristic of 2-way power divider with 2nd-order and 4th-order matching circuit.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.7
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• pp.22-27
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• 2001

In this paper, the complex permittivity of various dielectrics such as powder(sugar and flour) and solid(teflon and acrvl) are measured by using an open ended coaxial-line probe, which is self designed and manufactured, The probe is connected to a vector network analyzer(VNA) through a coaxial cable, The end of the cable is corrected by using an OSL(open, short, and load) calibration kit, The phase difference, which is produced by inserting the probe at the end of the line. is compensated by using the numerically calculated reflection coefficient of distilled water, The complex permittivity is reconstructed by inserting the measured reflection coefficient, which is produced at the interface between the probe and measuring material, into ,an virtual conical cable conversion model. Over a wide frequency range from 30 MHz to 3 GHz, the measured complex permittivitis of various powder and solid using the our method are compared with the results, which are measured by using an transmission-line method of the Korea Research Institute of Standards and Science(KRISS).

• Journal of Magnetics
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• v.21 no.3
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• pp.450-459
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• 2016

Experimental results and data of numerical simulations are presented, concerning generation of wideband radio frequency (RF) oscillations in a nonlinear transmission line (NLTL) which contains a pre-magnetized core of ferrite material. Emphasis is made on the means for extracting the RF signal from the line, in order to radiate it into free space. Antennas of two types that can be used for the purpose are considered, both featuring a coaxial design. This permits availing of the principal advantages of coaxial systems, such as operation in the mode of a traveling TEM wave; wide range of the transmitted frequencies, and a reasonably simple design. The antennas studied, specifically a disc-cone dipole (DCD) and an impulse reflector antenna ('Half-IRA', or HIRA type) differ significantly in effective width of the radiated spectrum and in spatial characteristics of the radiated field in far region.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.789-794
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• 2011

A coaxial-cable impedance transformer used in wideband frequency range is generally restricted to the fixed impedance transformation ratio as n2:1 or 1:n2(n: the number of coaxial cables). In this paper, we propose a new coaxial-cable impedance transformer to have an arbitrary impedance transformation ratio. We have fabricated three impedance transformers($50-{\Omega}$ to $25-{\Omega}$, $50-{\Omega}$ to $20-{\Omega}$ and $50-{\Omega}$ to $9-{\Omega}$) to confirm the operation characteristic of the suggested impedance transformer. The reflection characteristics (S11) of the fabricated $50-{\Omega}$ to $25-{\Omega}$ and $50-{\Omega}$ to $20-{\Omega}$ impedance transformer were less than -15dB over about 3-octaves frequency range and the reflection characteristic (S11) of the fabricated $50-{\Omega}$ to $9-{\Omega}$ impedance transformer was less than -15dB over about 1-octave frequency range, respectively.