• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.790-794
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• 2012

A output strength is limited according to the frequency used in order to protect other wireless stations from interference caused by radio waves emitted from the low power wireless installations. For receivers, unwanted spurious emission is regulated, and regulations in Korea define that additional spurious emission for receivers in the low power wireless installations under 1GHz should be -54dBm, but no regulations have been established yet for low power wireless installations over 1GHz. It is presently required to set domestic standards for devices over 1GHz on account of the expansion of the communication market and its service.

• ETRI Journal
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• v.34 no.1
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• pp.9-16
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• 2012

Precoding in the multiple-input multiple-output orthogonal frequency division multiplexing system is investigated. In conventional wideband precoding (WBP), only one precoder, obtained from the decomposition of the subcarrier independent channel matrix, is used for all subcarriers. With an investigation of the relationship between the subcarrier independent channel matrix and the temporal/frequency channels, an improved WBP scheme is proposed for practical scenarios in which a part of subcarriers are allocated to a user. The improved WBP scheme is a generalized scheme of which narrow-band precoding and conventional WBP schemes are special modes. Simulation results demonstrate that the improved WBP scheme almost achieves the optimum performance of a single precoder and outperforms the conventional WBP scheme in terms of the bit error ratio and ergodic capacity with slight complexity increase. The largest advantage of the improved WBP scheme on signal-to-noise ratio in simulation results is over 2.1 dB.

• Journal of the Korean Institute of Gas
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• v.3 no.2 s.7
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• pp.17-23
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• 1999

The wire and/or wireless data communication system for anti-disaster system of natural gas governor station was developed. In oder to prevent accidents of governor station, the operator was replaced by RTU(Remote Terminal Unit) which gather and transmit safety situation of governor station. The database and MMI(Man Machine Interface) were also developed to analyze the situation of governor station. The data communication between server and RTU was designed to switch automatically from wire to wireless communication and vice versa when one of them failed communication. We also have developed the patrol car management system which was applied GPS(Global Position System)/GIS(Geometric Information System), and the earthquake detection/transmission system which was adopted three dimension acceleration sensor. When a earthquake may occur, the earthquake detection/transmission system monitors data such as PGA(Peak Ground Acceleration), Sl(Spectrum Intensity) and orders the emergency shutoff valve close immediately.

• Journal of information and communication convergence engineering
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• v.12 no.1
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• pp.1-7
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• 2014

A novel design of a simple circular ring with open-ended monopole antenna for wireless local area network (WLAN) applications is proposed in this article. The proposed antenna consists of an open-ended circular ring and $50-{\Omega}$ microstrip feed-line. The proposed antenna is capable of generating two separate resonant modes with good impedance-matching conditions. A prototype of the proposed antenna is designed, fabricated, and measured. Acceptable agreement between the measurement and simulation results is achieved. Experimental results show that the proposed antenna has operating bandwidths of 1.99-3.04 GHz and 5.08-6.1 GHz with a return loss of less than -10 dB, covering the required bandwidths of the 2.4/5.2/5.8-GHz WLAN standards. This is a microstrip antenna for IEEE 802.11a/b wireless local area networks applications. Meanwhile, the two-dimensional (2D) radiation patterns and three-dimensional (3D) gain performance of the antenna are also observed and discussed.

• Journal of IKEEE
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• v.8 no.1 s.14
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• pp.79-85
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• 2004

In this paper, Sub harmonic mixer using anti-parallel diode pair is designed for 5.8 GHz Wireless LAN. Conventional mixers mix LO with RF and obtain IF signal from the difference between LO and RF. As frequency increase, LO signal is required increasing LO power, better phase noise, stable LO. But, using APDP, the SHP mixer mix the harmonics of LO signal. Therefore, Sub harmonic mixer is advantage that necessary LO signal frequency was used to operate the 1/2. When LO power is 3 dBm, the conversion loss of manufactured SHP mixer is 12.83 dB. The isolation of LO/IF, 2LO/IF, RF/IF and LO/RF is 39.17 dB, 58 dB, 34 dB, 67.9 dB. And IIP3 is 8 dBm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.4
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• pp.27-37
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• 2001

The design, fabrication, and an experimental implementation of the strip patch antenna coupled with a H-shaped aperture arc presented in this paper. The proposed antenna has the wide bandwidth, high gain, and low cross-polarization levels. We measured the VSWR, smith chart impedance characteristic, co/cross polarization pattern, gain, and so on. The measured bandwidth of this antenna is 47.1 %. To reduce the back lobe and increase the gain, when the reflector is used, cross polarization level is below -18.2dB at E-plane and below 25.7 dB at H -plane. The maximum gain at 2.05 GHz is also 10.4 dBi and the 3 dB gain bandwidth with center frequency at 2.17 GHz is 24 %, which is the wide bandwidth. This antenna can find applications in mobile communication, wireless LAN, RF communication system, and so on.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.12
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• pp.1075-1083
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• 2016

Nowadays, the use of wireless input devices has been increasing on the basis of high convenience and portability. In particular the most widely used wireless keyboard and the mouse to use the 2.4 GHz frequency band, but due to the third party receives the electromagnetic wave from leaking when the radio equipment it is easy to obtain the personal information and the vulnerability is also being reported consistently. In this paper, implement a system to analyze and manipulate the packets of 2.4 GHz wireless keyboard and mouse using USRP device and GNU Radio package for verify the vulnerability of 2.4 GHz wireless keyboard and mouse. Using the construction system has attained a equipment specific address and key information by analyzing the communication protocol and the packet structure of the device was proved that a user can operate the PC to send the random key from long distance.

• Journal of Broadcast Engineering
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• v.14 no.1
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• pp.70-80
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• 2009

We propose an ideal line coding for high speed data communication in visible light communication system. B4-HBT line coding is defined as follow. The 1 bit is +V at first though 1 encodes +Voltage and -Voltage doing change of shift each other, then -V newly. V that is been mutually contradictory for 1 bit that exist before that if continuous 0 bits exist 4 here same and reduces mistake because has reverse mark V in 4 continuous last 0 bits and gives half bit variation in 1 bit and made effect of noise low. 2${\sim}$3 dB profit is seen comparing with line coding that exist in simulation result.

• Journal of the Korea Society for Simulation
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• v.15 no.3
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• pp.87-91
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• 2006

With the growth of the internet, the number of wireless internet users has increased continuously up to date. However, mobile communications could not support high speed transmission rate with cheap communication fee and wireless LAN has problems in providing terminal mobility and wide area connectivity, respectively. So the WMAN standard has been newly designed to make up for these limits. The initial 802.16 specification effectively offers a solution for providing fixed users with high speed wireless communication but it does not offer terminal mobility. So the 802.16d and 802.16e have been developed as the next generation solution that can support various PHY layer (SC, SCa, OFDM, OFDMA) and offer the terminal mobility. In this paper, we propose an effective uplink scheduling algorithm for VoIP with using UGS, and we show that our proposed algorithm is superior in view of average delay and management of uplink bandwidth to conventional rtPS algorithm and the scheme in reference, with using NS-2 network simulator.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.3
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• pp.182-188
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• 2004

We demonstrate a $2.1\;{\times}\;1.0\;{\times}\;0.1cm^3$ sized compact transmitter using LTCC System-in-Package (SiP) technology for 60GHz-band wireless communication applications. For low-attenuation characteristics and resonance suppression of the SiP, we have proposed and demonstrated a coplanar double wire-bond transition and novel CPW-to-stripline transition integrating air-cavities as well as novel air-cavities embedded CPW line. The fabricated transmitter achieves an output of 13dBm at a RF frequency of 62GHz, an IF frequency of 2.4GHz, and a LO frequency of 59.6GHz. The up-conversion gain is 11dB, while the LO signal is suppressed with the image rejection mixer below -21.4dBc, and the image and spurious signals are also suppressed below -31dBc.