• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.5
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• pp.9-15
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• 2001

This paper describes measurement method of dielectric properties of dielectric materials using cylindrical cavity resonator's. Dielectric properties of concern here are relative permittivity, loss- tangent, quality factor and so on. An analysis of $TE_{011}$mode in dielectric properties of concentric dielectric-rod inserted cylindrical cavity resonator is presented. The frequency variation by the air gap at $TE_{011}$ mode turns out to be the least sensitive. A technique using a $TE_{011}$ mode of concentric dielectric-rod inserted cylindrical cavity resonator and an exact field representation of neo non-decaying mode are introduced for measurement of dielectric properties.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.9
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• pp.872-879
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• 2004

The TX/RX broadband L-type circular polarization antenna using LTCC(Low Temperature Co-fired Ceramic) for satellite communication at K, Ka band(20～21 GHz/30～31 GHz) has been presented. This antenna has been analyzed in compensation for LTCC with relative permittivity 5.2 and could have been integrated with RF component. Also antennas on LTCC enable :o reduce loss of RF system due to integrate with RF circuits and to light weight, and thus, generally one can reduce size of the RF system. As the geometry of this antenna presented is made simple by L type of monopole antenna, it is easily manufactured by LTCC progress and enables to reduce loss.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.1023-1029
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• 2010

In this paper, we proposed the broadband polarization diversity antenna operating in the PCS, WCDMA and WiBro band for mobile base station. We designed the antenna using the dipole antenna of the square loop type and microstrip feeding structure. Additionally, we used the choke box to remove the distortion of radiation patterns by the reflector structure when operating broadband. The simulation was performed using MWS in a commercial tool of CST company and the antenna was fabricated on a teflon substrate with 3.33 of the relative permittivity. The proposed antenna has the bandwidth of 640 MHz(from 1.75 to 2.39 GHz) when VSWR is below 1.5. At the operating bands, the interisolation between the cross-pair radiators is less than -25 dB and the maximum gains for PCS, WCDMA and WiBro band are 8.9, 8.2 and 8.6 dBi, respectively.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.543-548
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• 2011

In this paper, H-polarized electromagnetic scattering problems by a resistive strip grating over a grounded dielectric plane according to the strip width and grating period, the relative permittivity and thickness of a dielectric layer, and incident angles of a TE (transverse electric) plane wave are analyzed by applying the FGMM (Fourier-Galerkin Moment Method). The tapered resistivity of resistive strips in this paper varies from finite resistivity at one edge to zero resistivity at the other edge, then the induced surface current density on the resistive strip is expanded in a series of Jacobi polynomials of the order ${\alpha}=1$, ${\beta}=0$ as a kind of orthogonal polynomials. The numerical results of the normalized reflected power show in good agreement with those of existing papers.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.371-375
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• 2014

In this paper, the solutions of TE(transverse electric) scattering problems by a resistive strip grating over a grounded dielectric layer are analyzed by applying the PMM(point matching method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients and the resistive boundary condition is used for the relationship between the tangential magnetic field and the induced surface current density on the resistive strip. The induced surface current density of resistive strip is obtained by difference of the up and down of the magnetic field in two boundary areas of the resistive strip. The numerical results for reflected power of zeroth order mode analyzed by according as the resistivity, the width and spacing of resistive strip, the relative permittivity and thickness of dielectric layer, and incident angles. The numerical results shown in good agreement compared to those of the existing papers using FGMM(fourier galerkin moment method).

• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.838-845
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• 2009

In order to obtain magneto-dielectrics with various permmittivity and permeability which could be used as the antenna substrate, various magneto-dielectrics compounded of dielectric materials(such as silicon and epoxy resin) and magnetic materials(such as carbonyl iron, barium and strontium powder) were fabricated. The relative permittivity and permeability of those were measured by use of HP 4291B impedance analyzer. Based upon the measured results, inverted-F meander monopole antennas(IFA) which were printed on the magneto-dielectric substrates fabricated as film type were designed and fabricated to investigate into variations of antenna characteristics such as the resonant frequency and impedance bandwidth in comparison with use of dielectric substrate. Some simulated and measured results for the designed IFA were presented. Characteristics of magneto-dielectrics which are different according as the choice of magnetic material or the composition ratio between magnetic material and dielectric material is different have been discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.884-890
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• 2003

In order to reduce the specific absorption rate(SAR) in a human head exposed to electromagnetic fields radiated by a cellular phone, we have analyzed an electromagnetic wave absorber attached to the handset. A manufactured electromagnetic wave absorber was composed of Mn - Zn, which had complex relative permittivity of 7.30-j0.05 and permeability of 2.20-i1.55. The SAR value from the electromagnetic wave absorber attachment was calculated by using the nonuniform finite difference time domain(FDTD) algorithm and measured by phantom model at 835 MHz. The SAR reduction due to the electromagnetic wave absorber are about 18 % at 835 MHz. The V.S.W.R and radiation pattern of antenna are good agreement with the normal antenna. The gain reduction due to the electromagnetic wave absorber are only 0.3 dB at 835 MHz. But the sensitivity of cellular phone generally improves about 1 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.277-290
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• 1999

A simulation using the finite-difference time-domain method to analyze the electromagnetic interactions between a cellular phone and the human body was conducted, and a synthesis of a bone-equivalent material to make a human head phantom was performed. A test model of the cellular phone was fabricated to measure its reflection coefficient and radiation pattern in the free space. Various effects of the human body on the characteristics of the phone, such as input impedance, reflection coefficient, radiation pattern, and radiation efficiency are analyzed as the distance between the head and the phone antenna varies. When the phone was operated close to the head, the resonant frequency of the antenna decreased by up to 12%. With the output power of 0.6W, as long as the distance was larger than 30mm, the 1-g averaged peak SAR was below the ANSI/IEEE safety guideline, 1.6 W/kg. To synthesize the bone-equivalent material, an epoxy with hardener and a graphite powder were used as basis ingredients, and a small amount of a conducting epoxy was added to control the conductivity of the material. A material having a relative permittivity of 18.04 and a conductivity of 0.347, which are close to those of the bone at 850 MHz, was synthesized.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.1
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• pp.286-290
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• 2017

In this paper, we have proposed a hexagonal patch UWB antenna with a band notch characteristic where the notch band of 5.15 ~ 5.85 GHz band of WLAN was induced by inserting a circular slit in the patch. The impedance bandwidth of the proposed antenna meet the band width criteria of UWB communication system where is mentioned as frequencies range form 3.1 ~ 11.8 GHz. The characteristic band at 5.2 ~ 5.8 GHz notch band was observed. The radiation pattern of the antenna shows a directinal radiation pattern at $0^{\circ}$ and $180^{\circ}$ in XZ-plane and YZ-plane is an omni-directional pattern, respectively. In addition, it is observed that increase in frequency results in increases of the antenna gain whereas the notch band section is decreased. The proposed antenna was designed TRF-45 substrate with thickness of 1.62 mm, a loss tangent of 0.0035, a relative permittivity of 4.5 and designed were used Ansys Inc. HFSS.

• Journal of the Korean Ceramic Society
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• v.39 no.7
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• pp.628-634
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• 2002

Formation rate of tetragonal BaTiO$_3$powder by hydrothermal synthesis and its dielectric property were studied. Submicron tetragonal BaTiO$_3$ powders were prepared hydrothermally, using Ba(OH)$_2$.8$H_2O$, TiO$_2$(anatase) and KOH as starting chemicals. Characterization via X-ray diffractometry, field emission scanning electron microscopy confirmed that increasing calcination temperatures(from 1100 to 130$0^{\circ}C$) promotes the formation of tetragonal BaTiO$_3$. Tetragonal BaTiO$_3$ ceramics, obtained by calcining at 1200 for 3 h after hydrothermal synthesis at 200 for 168 h, exhibited submicron size of 0.5 ~ 0.7 ${\mu}{\textrm}{m}$ and high relative permittivity.