• The Journal of Engineering Geology
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• v.15 no.3
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• pp.281-288
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• 2005

To evaluate a property of moisture distribution and volumetric water content on bentonite media the responses of complex dielectric constant were used which are measured by Frequency Domain Reflectometry with Vector Network Analyzer (FDR-V) system. The bentonite is widely used a barrier liner system in the waste disposal site, recently. In case of barrier liner system, generally, the coefficient of permeability should have to less than 10-7cm/sec. According to the results, the complex dielectric constants are increasing with increase the volumetric water content and temperature together. Also the variation of complex dielectric constant due to temperature gradient is confirmed that the moisture movements are increasing with the variations of temperature from high range to low range, which is represented the property of moisture distribution in the bentonite.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.36-41
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• 2005

복소유전율상수인 실수부(Real part)와 허수부(Imaginary part)를 측정하기 위하여 Frequency Domain Reflectometry with Vector Network Analyzer(FDR-V) 측정 장비로 $1{\sim}18GHz$ 범위 내에서 매질의 기본 구성단위인 공기, 물, 흙입자에 대한 기본적인 유전율 특성을 파악하고, 이들로부터 다공질 매질내 유류 오염물질의 함유 특성을 측정할 수 있다. 또한 제작된 시료에 대한 포화도와 1GHz 범위에 분포하는 실수부 유전율상수와의 관계로부터 매질의 공극내 함유된 물질의 유전율상수 특성에 매우 민감한 반응을 보이므로, 이들로부터 매질의 공극률 내지 유효공극률의 측정이 가능할 것으로 사료된다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.11
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• pp.9-19
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• 1990

A theoretical analysis and measurement technique to determine the complex permittivity and permeability of cylindrical and ring type dielectric resonators is given. The resonant frequency, unloaded quality factor and physical dimensions of dielectric resonator placed between two parallel conducting plates are used to evaluate the complex permittivity and permeability. This process is repeated for other higher-order modes to expand the evaluation at higher resonant frequencies. The nature of each mode is identified by measuring the variations of field strength along the azimuthal and longitudinal direction. An error analysis taking into account various error sources reveals that $TE_{0np}$ or quasi-TE modes yield the least amount of measurement error, which is less than $0.5{\%}$for the real part, $4{\%}$for the imaginary part of complex permittivity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.52-59
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• 2006

To construct its complex permittivity from the reflection coefficient of a thin film such as PCB substrate measured by open-ended coaxial probe, an integral equation is formulated using modal analysis and equivalent source. The accuracy of the conversion model based on the integral equation is confirmed in both cases of converted complex permittivities calculated from numerically computed and actually measured reflection coefficients. And the maximum valid frequency of open-ended coaxial probe is limited by the size of its flange.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.5
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• pp.493-498
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• 2004

The complex permittivities of methanol measured from 0.2 to 2.0 ㎓ using an open-ended coaxial probe revealed the large deviation from the given data in literature. In this paper, it was investigated whether the given or measured complex permittivity is similar to the real value of our methanol used for experiment. The FDTD method was applied to confirm the effect of our conversion model excluding the effect of sufficiently small measurement error. The complex permittivities reconverted from the computed reflection coefficient by employing our improved conversion model were not similar to the given value but measured value. These results assured the accuracy and stability of our measurement-and-conversion process.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.5
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• pp.17-24
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• 2000

Complex permittivity of dry sand is measured by using an open-ended coaxial probe, which was self-designed and manufactured. As a simple calibration scheme of the probe, the phase difference between the measured and the calculated reflection coefficients of pure water is subtracted from the phase of the measured reflection coefficient for dry sand. And then the complex permittivity of dry sand is reconstructed by applying its measured reflection coefficient into an improved imaginary transmission-line model. The accuracy of our measurement scheme is verified by showing that its reconstructed complex permittivity approaches the precise value of dry sand.

• Journal of the Korean Magnetics Society
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• v.22 no.6
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• pp.210-215
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• 2012

The absorption performance of a metal-backed single layered electromagnetic wave absorber is optimized at matching conditions of thickness and frequency indicating the maximum returns loss of incidence electromagnetic wave in the contour map. These matching conditions are obtained by applying the electromagnetic impedance to the transmission line theory, which depend on the complex permeability and complex permittivity of absorber material. The magnetic materials with high permeability can enhance the matching thickness condition to the wide frequency range based on the decrease of permeability with frequency and it can be used as a wideband electromagnetic wave absorber material. Therefore, the magnetic materials with higher saturation magnetization and lower permittivity than NiZn ferrite can be applied to the wideband electromagnetic wave absorber in order to satisfy the newly enforcing the electromagnetic compatibility regulation in the future.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.1 s.92
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• pp.33-39
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• 2005

Complex permittivities of material in a wide bandwidth are measured by using an open-ended coaxial probe. To obtain a confident complex permittivity profile, the accuracy of measured reflection coefficients and the stability of the conversion model should be guaranteed in advance. In this paper, the sensitivity of our conversion model is analyzed by employing two instruments with different uncertainties. And various factors effected on the accuracy of measured reflection coefficients are investigated in experiment.

• Polymer(Korea)
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• v.25 no.1
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• pp.98-107
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• 2001

Dielectric properties and shape memory characteristics of SBS composites filled with carbon black as conductive filler and (Ba,Ca)$(Sn,Ti)O_3$ or $SrTiO_3$ as dielectrics were investigated for the development of phantom model. SBS/carbon black composite showed an increment of complex dielectric constant with increasing the content of carbon black and the frequency dependence that the dielectric constant decreases with the frequency. The complex dielectric constant and the conductivity of SBS/carbon black/dielectrics composites increased with the increase of dielectrics and the characteristics of the frequency dependence also occurred by the effect of carbon black. Phantom materials with the dielectric properties and the conductivity corresponding to human tissues for the measurement of specific absorption rate(SAR) within the frequency range of current mobile phones(775MHz~2GHz) could be developed by adjusting the composition ratios of carbon black, dielectrics and SBS and by controlling the characteristic of frequency dependence of composite. From thermomechanical cycling test good shape recoverability could be obtained in SBS composite even though the residual strain was increased by the effect of filler.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.72-75
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• 2000

This paper investigates the complex permittivity of foam materials using the rectangular waveguide. The transmission coefficients of materials inserted in the waveguide are measured with a network analyzer and calculated from the equivalent transmission line model. We use the trial and error method in the acquisition of the complex permittivity.