• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.69-76
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• 2015

This paper presents the results of an investigation into the frequency-dependent electrical parameters for different types of soil as a function of moisture content. The frequency dependence of soil electrical parameters is very important in the design of grounding systems. In fact, the performance of grounding systems is greatly dependent upon various factors such as soil type, particle size, water content, temperature, frequency, and the like. The resistivity and relative permittivity for four different soils were measured and analyzed in the frequency range of 1kHz - 1MHz. Soil resistivity declined as moisture content and frequency increased. In particular, the frequency dependence of soil resistivity was significant as the moisture content was low. In contrast, the relative permittivity of soil dramatically declined at the frequency of 10kHz or below as the moisture content increased, showing the opposite pattern in terms of variation patterns, compared to resistivity.

• Journal of electromagnetic engineering and science
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• v.8 no.3
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• pp.110-113
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• 2008

In this paper, we designed and fabricated an electromagnetic(EM) wave absorber for automotive radar in cars using $TiO_2$ as a dielectric material and chlorinated polyethylene(CPE) as a binder. First of all, we confirmed that the optimum composition ratio of $TiO_2$ was about 70 wt.%. The complex relative permittivity of a sample containing $TiO_2$: CPE=70:30 wt.% was calculated from S-parameter. The EM wave absorption abilities were simulated for the EM wave absorbers of different thickness using the calculated relative permittivity, and the EM wave absorber was manufactured based on the simulated design. A comparison of simulated and measured results is in good agreement. Measurement shows that a 1.85 mm thick absorber has absorption ability higher than 20 dB in the frequency range of $76{\sim}77$ GHz for automotive radars.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1738-1745
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• 2015

Radiation characteristics of a probe-fed rectangular microstrip patch antenna printed on a finite grounded high permittivity substrate are investigated systematically for various square grounded dielectric substrate sizes with several thicknesses and dielectric constants by experiment and full wave simulation. The effect of the substrate size on the radiation characteristics of a rectangular patch antenna is mainly determined by the effective dielectric constant of surface waves on a grounded dielectric substrate. As the effective dielectric constant of surface waves increases, the substrate sizes for the maximum broadside gain and the required onset for a large magnitude of squint angle decrease, while the variations of the broadside gain, the front-to-back ratio, and the magnitude of squint angle versus the substrate size increase due to the increase of the power of the surface wave.

• Journal of Powder Materials
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• v.15 no.1
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• pp.18-22
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• 2008

The electromagnetic (EM) wave absorption properties with a variation of crystallization annealing temperature have been investigated in a sheet-type absorber using the $Fe_{73}Si_{16}B_7Nb_3Cu_1$ alloy powder. With increasing the annealing temperature the complex permeability (${\mu}_r$), permittivity (${\varepsilon}_r$) and power absorption changed. The EM wave absorber shows the maximum permeability and permittivity after the annealing at $610^{\circ}C$ for 1 hour, and its calculated power absorption is above 80% of input power in the frequency range over 1.5 GHz.

• Journal of the Korea Safety Management & Science
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• v.3 no.3
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• pp.231-241
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• 2001

The epoxy resin materials used in outdoor high voltage equipments are required to have the high electric performance because of the miniaturization. The frequence dependence of the permittivity and the loss tangent have important information. In this paper we describe the frequency dependence of the permittivity and the loss tangent for epoxy resin filled with silica and the influence of filler shapes on the dielectric properties. The increment of tan $\delta$ in the low frequency region is caused by the increment of both the electrical conductivity and the polarization due to the shape of filler and the water absorbed in and near the interface between fillers and resins. The result of charge current and discharge measure, electric conduction is increased according to voltage.

• 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.

• Journal of electromagnetic engineering and science
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• v.1 no.2
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• pp.139-145
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• 2001

In this paper, a coaxial sample holder is proposed with its de-embedding and parameter extraction procedure. The S-parameters were measured up to 1 GHz using network analyzer, HP8753D, and N-type connector together with the de-embedding of N-type connector. The proposed de-embedding procedure is performed to extract electrical parameters of blood glucose, which gives the permittivity of blood glucose. We also analyzed the error of extracted parameters, which are caused by instrument error and geometrical error. Using these error analyses, we reduced the error factors of extracted parameters. We extracted electrical parameters of glucose samples through these all extraction procedure and confirmed the possibility of glucose diagnosis system based on microwave system.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.446-449
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• 1988

A spectral inverse technique, which was developed by applying the pulse basis moment method procedure on the direct scattering problem in the reverse sequence for the reconstruction of complex permittivity profiles inside inhomogeneous dielectric objects, is modified to be applicable to the moment method with series-expanded basis. By performing numerical simulations for various type of dielectric objects, it is demonstrated that this inverse technique provides close reconstruction of permittivity profiles. Futhermore, compared to the previous scheme of the pulse basis, the presented method is shown to reduce the computation cost, relative error of reconstructed permittivity profiles by averaging in each cell, and the ill-posedness inherent to this inverse scattering problem.

• Journal of Navigation and Port Research
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• v.34 no.2
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• pp.111-115
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• 2010

In this paper, the electromagnetic (EM) wave absorbers using TiO2 as a dielectric material with chlorinated polyethylene (CPE) were investigated in W-band radio frequencies. We compared the relative permittivity with reflectionless curve and the absorption properties of samples containing 40 wt.%, 50 wt.%, 60 wt.%, 70 wt.%, and 80 wt.% TiO2. It is possible to realize a complex relative permittivity satisfying the reflectionless condition by choosing composition ratio of TiO2. The optimized composition ratio of TiO2 for the maximum absorption property is about 70 wt.%. As a result, we have confirmed the realization of an EM wave absorber with a high absorption property in W-band radio frequencies.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.4
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• pp.11-19
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• 1993

The complex permittivity and the linewidth of microwave ferrites are measured using the well known cavity perturbation method. The cavity perturbation method has been widely used for the measurement of complex permittivity and conductivity of low loss magnetic and dielectric materials at microwave frequencies. TT1-2000, TT73-2200, and G-113 samples ordered from Trans-Tech Inc, are tested. TE$_{103}$ and TE$_{106}$ rectangular waveguide cavities are fabricated and the ferrite sample of cylidrical rod and sphere shapes are prepared. The error between the measurement values and the supplier's data is less than 1 percent in case of $\varepsilon$’ and about 10 percent in case of linewidth ($\Delta$H). Worst case error analysis shows that our measured results are well within the error bound calculated from the accuracy specification of the measuring instruments.