• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1083-1090
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• 2004

In this paper, a meander-type microstrip patch antenna for application in 5GHz-hand is designed and fabricated To obtain enough bandwidth in VSWR≶2, the foam is inserted between substrate and ground plane, the coaxial probe source 1S used Antenna is simulated varing the length and width of meander line, the position of probe feeding and the thick of airgap. Later antenna is fabricated with optimizated antenna parameter. The measured result of Fabricated antenna obtained IGHz(l7.5%) bandwidth in VSWR≶2, the gain of 7.3-9.5dBi, Unidirectional pattern.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.7
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• pp.71-78
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• 2010

The objective of this research is to investigate the influence of material characteristic and design on to the electromagnetic interference (EMI) shielding characteristics. Basalt glass fiber reinforced composite specimens with stainless fiber conductive filler were manufactured to perform the electromagnetic interference shielding effectiveness(SE) experiments. In order to reflection and absorb the specimen in electromagnetic fields, flanged coaxial transmission line sample holder was fabricated according to ASTM D 4935-89. Electromagnetic shielding effectiveness(EMSE) was measured quantitatively to examine the electromagnetic shielding characteristics of designed specimens. The result of EMI shielding experiments showed that maximum EMSE value of sandwich type specimens with GSG(basalt glass fiber/stainless fiber/basalt glass fiber) and SGS(stainless fiber/basalt glass fiber/stainless fiber) were 65dB and 80dB at a frequency of 1,500MHz, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.619-626
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• 2000

The electromagnetic fields of the corrugated annular feed-horn antenna have been analyzed exactly by using the finite-difference time-domain (FDTD) technique. The radiation pattern and return loss characteristics of the antenna were obtained as a function of the impedance of feeding coaxial line at 11.8GHz. The return loss was determined to be less than -25dB at 30$\Omega$. It was confirmed that the phase error is less compared to that of the antenna without corrugation, but the directivity of the radiation pattern needs to be improved.

• Journal of the Korea Society of Computer and Information
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• v.13 no.6
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• pp.211-216
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• 2008

Gap fillar antennas are needed for serving the high quality of DMB through the cellular phone by eliminating the shadow regions among buildings or underground. We implement Quadrifilar Helical Antenna using phase difference with PCB feeding lines without coaxial cables and four impedance matching circuits. It is shown that the antenna characteristics is affected by the size and diameter through the simulation process using MicroWave Studio and it is applied for implementing QHA. Experiment results confirm that the performance can be gained as same as the simulation data by using the phase difference with PCB feeding lines without additional impedance matching circuits.

• Journal of Magnetics
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• v.21 no.1
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• pp.61-64
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• 2016

In this study, we report the as-prepared MgO-doped $BaFe_{12}O_{19}$, which was prepared by calcination technique and high-energy ball milling process, as an electromagnetic wave absorber. The phase analysis of $BaFe_{12}O_{19}$ and the as-prepared MgO-doped $BaFe_{12}O_{19}$ was detected utilizing X-ray Diffractometer (XRD). The microstructure was characterized using Scanning Electron Microscope (SEM). By means of the transmission/reflection coaxial line method, the electromagnetic properties and microwave absorbing properties of the as-prepared electromagnetic wave absorber were studied. It is found that the electromagnetic wave absorber has a minimum reflection loss value of -41 dB at 4.27 GHz with a matching thickness of 2.6 mm. The experiment results revealed that the as-prepared electromagnetic wave absorber could find potential applications in many military as well as commercial industries.

• Journal of electromagnetic engineering and science
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• v.14 no.4
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• pp.360-366
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• 2014

A single-feed composite cavity-backed four-arm curl antenna is presented for use in global positioning systems (GPS). Its primary radiating element is fed by a vacant-quarter printed ring, which helps the antenna directly match to a $50-{\Omega}$ coaxial line and produce a good circular polarization (CP). The cavity-backed reflector is employed to improve the CP radiation characteristics in terms of 3-dB axial ratio (AR) beamwidth and minimum AR value. The optimized design with an overall size of $90{\times}90{\times}25mm^3$ ($0.4725{\lambda}_o{\times}0.4725{\lambda}_o{\times}0.13{\lambda}_o$ at 1,575 MHz) results in a ${\mid}S_{11}{\mid}<-10dB$ bandwidth of 8.66% (1,514-1,651 MHz) and a 3-dB AR bandwidth of 2.23% (1,555-1,590 MHz). The antenna radiates a widebeam right-hand circular polarization and operates with a measured radiation efficiency greater than 90% within its impedance matching bandwidth.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.1971-1978
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• 2016

In this paper, electrical and physical characteristics associated with the ionization growth of soil under impulse voltages in a coaxial cylindrical electrode system to simulate a horizontally-buried ground electrode were experimentally investigated. The results were summarized as follows: Transient ground resistances decreased significantly by soil ionization. The voltage-current (V-I) curves for non-ionization in soil lined up in a straight line with the nearly same slope that is the ground resistance, but they showed a 'cross-closed loop' of ${\infty}$-shape under ionization. The conventional ground resistance and equivalent soil resistivity were inversely proportional to the peak value of injected impulse currents. On the other hand, the equivalent ionization radius and time-lag to the maximum value of ionization radius were increased with increasing the incident impulse voltages. An analysis method for the transient ground resistances of the ground electrode based on the ionization phenomena was proposed. The proposed method can be applied to analyze the transient performances of grounding systems for lightning protection in power system installations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4A
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• pp.312-319
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• 2005

In this paper, a meander-type microstrip patch antenna for application in 5GHz-band is designed and fabricated. To obtain enough bandwidth in VSWR<2, the foam is inserted between substrate and ground plane, the coaxial probe source is used. Antenna is simulated varing the length and width of meander line, the position of probe feeding and the thick of airgap. Later anterlna is fabricated with optimizated antenna parameter. The measured result of Fabricated antenna obtained $1GHz(17.5\%)$ bandwidth in VSWR<2$, the gain of $.3\sim9.5$dBi, Unidirectional pattern.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.169-174
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• 2012

Electromagnetic interference(EMI) shielding effectiveness(SE) was investigated in of woven fabric made of epoxy/copper-nickel fabrics and nickel coated carbon fiber reinforced acrylonitrile-butadiene-styrene(ABS) composites. The coaxial transmission line method was used to measure the EMI shielding effectiveness of the composites. We designed and constructed a measuring system, consisting of a network analyzer and a device that plays the serves as a sample holder and at the same time as a transmission medium of the incident electromagnetic wave. The measurement of SE were carried out frequency range from 100MHz to 2GHz. It is observed that the SE of the composits is the frequency dependent increase with the increase in nickel coated carbon fibre volume fraction. The nickel coating with 20wt% ABS composite was shown to exhibit up to 60dB of SE. The result that nickel coated carbon fibre ABS composite can be used for the purpose of EMI shielding as well as for some microwave applications.

• Journal of electromagnetic engineering and science
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• v.14 no.3
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• pp.299-305
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• 2014

A wideband circularly polarized (CP) antenna with a single feed is proposed for use in global navigation satellite systems. Its primary radiation elements are composed of two orthogonal bowtie dipoles, which are equipped with double-printed vacant-quarter rings to allow direct matching of the antenna to a single $50-{\Omega}$ coaxial line and to produce CP radiation. The crossed bowtie dipole is appropriately incorporated with a planar metallic reflector to produce the desired unidirectional radiation pattern as well as to achieve a wideband characteristic in terms of impedance matching and axial ratio (AR) bandwidths. The designed antenna was fabricated and measured. The prototype antenna with an overall 1.2-GHz frequency size of $0.48{\lambda}_o{\times}0.48{\lambda}_o{\times}0.25{\lambda}_o$ produced a measured ${\mid}S_{11}{\mid}$<-10 dB bandwidth of 1.05-1.79 GHz and a measured 3-dB AR bandwidth of 1.12-1.64 GHz. It also showed right-hand CP radiation with a small gain variation (${\pm}0.3dB$) and high radiation efficiency (>93%) over the operational bandwidth.