• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1994.06a
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• pp.264-269
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• 1994

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2225-2227
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• 2001

A wireless communication module for multiple nearfiled measurement and control module was developed. The function of the developed system are dual communication, concurrent multiple communication, PLC control, and A/D, D/A converting. The multiple communication approach is based on master-slave with sub-polling scanning concept.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3487-3494
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• 2013

Diverse application service such as mobile payment, access control or smart poster have been provided by using smart devices with built-in Near Field Communication technology. Especially, a mobile payment system can provide convenience to its users, but it also can poses including data disclosure while transmitting. There are vulnerabilities while generating session keys used to encrypt data in transaction processes as proposed in KS X 6928, the standard for mobile payment system. Therefore, in this thesis, I analyzed weaknesses of session keys used to encrypt transaction data and proposed a more secure mobile payment system based on NFC to enhance security. The proposed system will provide security functionalities such as key freshness, mutual authentication and key confirmation.

• Journal of Industrial Convergence
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• v.16 no.3
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• pp.33-40
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• 2018

Near Field Communication has been emerged as a spectacular phenomenon. The aim of this study is to determine the factors influencing the adoption of NFC-enabled mobile payment. In order to analyze, this study proposes a research framework based on Technology Acceptance Model. 353 valid data were collected through the Internet who has used NFC technology. Results show that relative advantage, social influence, and technology availability have a significant effect on perceived usefulness ($0.190{\ast}{\ast}{\ast}$, $0.211{\ast}{\ast}{\ast}$, $0.227{\ast}{\ast}{\ast}$respectively). However, for perceived ease of use, only relative advantage and social influence were verified to have significant influence. Perceived ease of use significantly influence perceived usefulness ($0.348{\ast}{\ast}{\ast}$), and both of them significantly affect the NFC-payment adoption intention ($0.199{\ast}{\ast}$, $0.361{\ast}{\ast}{\ast}$). The results also verified the moderator variable of personal innovativeness ($0.20{\ast}{\ast}{\ast}$ and $0.297{\ast}{\ast}{\ast}$respectively).

• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.18-24
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• 2010

A Ka-band microstrip array antenna for wide-range detection of moving targets is analyzed through a photonicassisted reactive-near-field characterization technique. The antenna array employs a 3-dB-tapered feed network to suppress the sidelobe level while retaining a wide azimuth beamwidth for a wide detection range. The relative nearelectric field patterns of the array and its 3-dB-tapered feed lines have been measured using an electro-optic fieldmapping technique for minimally invasive millimeter-wave sensing. A number of typical limitations on the technique, involving bandwidth, low signal-modulation depth, and high laser-induced noise in high-frequency applications, have been overcome by suppressing the carrier portion of the optical interrogation beam.

• The Journal of the Acoustical Society of Korea
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• v.36 no.2
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• pp.100-107
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• 2017

The focused MVDR (Minimum Variance Distortionless Response) can be applied for source localization in near field. However, if the number of sensors are increased, it requires a large amount of calculation to obtain the inverse of the covariance matrix. In this paper we propose a focused MVDR method using that beam space is formed from output of far field beamformer at the subarray. The performances of the proposed method was evaluated by simulation. As a result of simulation, the proposed method has the higher spatial resolution performance then the conventional delay-and-sum beamformer.

• Journal of Powder Materials
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• v.21 no.6
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• pp.429-433
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• 2014

This study investigated the magnetic properties and frequency dispersion of complex permeability of Ni-Zn-Co ferrites used for magnetic shielding in near field communication (NFC) system. The sintered specimens of $(Ni_{0.7}Zn_{0.3})_{1-x}Co_xFe_2O_4$ composition were prepared by the conventional ceramic processing. The coercive force and saturation magnetization were measured by vibrating sample magnetometer. The complex permeability was measured by RF impedance analyzer in the range of 1 MHz~1.8 GHz. The coercive force increased and saturation magnetization decreased with increasing the Co substitution. The real and imaginary parts of complex permeability decreased and the resonance frequency increased with Co substitution, which was attributed to the increase in crystal anisotropy field and reduction in saturation magnetization. The effect of Co substitution could be found in reducing the magnetic loss to nearly zero at the operating frequency of NFC (13.56 MHz).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.2
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• pp.43-50
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• 2022

In this paper, we designed and verified a Far-field measurement system for measuring the performance of an antenna operating in millimeter wave(W-band). For the antenna test, a measurement system should be selected according to the type of antenna, measurement items, measurement environment and period, etc. In the case of near-field measurement, it takes a lot of time because the number of measurement items increases when the antenna has multiple channels or various beams. Such an antenna can reduce the measurement time through Far-field measurement, and only necessary measurement items can be measured. Therefore, this study secured precise alignment of the far-field measurement system using a high-power laser and improved the measurement accuracy by applying a double amplifier system. The designed system was built in the anechoic chamber and verified by comparison with the verified Near-field measurement system.

• Journal of IKEEE
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• v.24 no.4
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• pp.1064-1068
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• 2020

For LW-TLM antenna of 65 kHz, Near-field propagation characteristics due to wave propagation obstacle are analyzed in this paper. The simulation modeling for propagation effects are based on the model of actual LW-TLM antenna which utilizes the frequency of 65 kHz, and the model expressed as propagation obstacle at a mountain height and a proximity of antenna and mountain. The near-field performance are analyzed based on the parameters of simulation model. In case of a normal mountain height and distance between the adjacent mountain and antenna site, a field strength change of about 1.7 dB has occurred. Above the constant distance of propagation obstacle and antenna, the wave propagation characteristics of disregarding the effects of propagation obstacle are shown. The results of this paper can be used to design and build a transmitting antenna site with 65 kHz operating frequency.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.11
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• pp.28-33
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• 2002

In this paper, the impedance-tuned monopole microstrip antenna designed for PCS is analyzed using finite difference time domain(FDTD) method. The perfectly matched layer(PML) absorbing material condition proposed by Berenger is used for the truncation of finite difference time domain lattice. A Gaussian pulse is selected as an excitation signal and a resistive voltage source model is used to reduce the error caused by the reflection waves. The FDTD method is inherently a near field technique. Therefore, the near field to far field transformation is need to compute far field antenna parameters such as radiation patterns and gain. The near field to far field transformation can be done both in the time domain and the frequency domain. We use the frequency domain transformation to compute the far field radiation patterns at single frequency. All the numerical results obtained by the FDTD method are compared with simulation results using the HFSS software. Good agreements are obtained in all cases.