• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.531-532
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.519-520
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• 2009

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.2
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• pp.111-117
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• 2019

We investigated the variations in the magnetic-field distribution and power transmission efficiency, resulting from changes in the relative positions of the transmitting and receiving coils, for electromagnetic-induction-type wireless power transmission using an elliptical receive coil. Results of simulations using a high-frequency structure simulator were compared to actual measurement results. The simulations showed that the transmission efficiency could be maintained relatively stable even if the alignment between the transmitting and receiving coils was changed to some extent. When the centre of the receiving coil was perfectly aligned with the centre of the transmitting coil, the transmission efficiency was the maximum; however, the degree of decrease in the transmission efficiency was small even if the centre of the receiving coil moved by ± 10mm from the centre of the transmitting coil. Therefore, it is expected that the performance of the wireless power transmission system will not be degraded significantly even if perfect alignment is not maintained. The results suggested a standardized application method of wireless transmission in the utilization of wireless power for implantable sensors.

• ETRI Journal
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• v.37 no.4
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• pp.727-735
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• 2015

This paper deals with the problem of blind source separation (BSS), where observed signals are a mixture of delayed sources. In reference to a previous work, when the delay time is small such that the first-order Taylor approximation holds, delayed observations are transformed into an instantaneous mixture of original sources and their derivatives, for which an extended second-order blind identification (SOBI) approach is used to recover sources. Inspired by the results of this previous work, we propose to generalize its first-order Taylor approximation to suit higher-order approximations in the case of a large delay time based on a similar version of its extended SOBI. Compared to SOBI and its extended version for a first-order Taylor approximation, our method is more efficient in terms of separation quality when the delay time is large. Simulation results verify the performance of our approach under different time delays and signal-to-noise ratio conditions, respectively.

• Journal of information and communication convergence engineering
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• v.8 no.2
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• pp.150-154
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• 2010

In this paper, the adaptive interference cancellation system (ICS) in order to cancel the feedback signal in the wireless communication system is proposed. We cancel the interference with the attenuation signal corresponding to the feedback signal and estimate the feedback signal by using Normalized Least Mean Square (NLMS) algorithm. The proposed scheme showed a better performance of interference cancellation in the measurement results.

• Journal of Sensor Science and Technology
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• v.15 no.5
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• pp.362-370
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• 2006

The wireless sensor network (WSN) based ECG and body temperature measuring system for ubiquitous health-care were designed and developed. The system was composed of a wireless sensor network node, base station and server computer for the continuous monitoring of ECG signals and body temperatures of patients at home or hospital. ECG signal and body temperature data, important vital signals which are commonly used in clinical and trauma care, were displayed on a graphical user interface (GUI). The data transfer from sensor nodes on patients' body to server computer was accomplished through a base-station connected to a server computer using Zigbee compatible IEEE802.15.4 standard wireless communication. Real-time as well as historical, ECG data of elderly persons or patients, can also be retrieved and played back to assist the diagnosis. The ubiquitous health care system presented in this study can effectively reduce social medical expenses, which will be increased greatly in the coming aging society.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.9-14
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• 2008

Ubiquitous implementation of indoor location-based technology is recognized that one of the important elements of the technology. Specifically, the hospital management of patients, the silver-town management, the implementation of the smart home for the indoors rather than outdoors in a range of broadband users for location-aware technology is needed. This paper in wireless devices with an indoor location awareness shows about the system's technical design and implementation. Location-based technology for wireless LAN users aware of the strength of radio signals (Received Signal Strength Indication, RSSI) using trilateration. Topographic mapping system will be implemented wireless devices and servers, Access Point (AP), which is the system's development and testing throughout the physical environment to determine the potential for real-life applications.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.173-177
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• 1998

Under indoor environment, in case that wireless optical LAN does not obtain the line-of-sight between transmitter and receiver, hemi-spherical lens or reflector must be adopted to get broader beam width. The beam tilt and the fluctuations in amplitude and phase of optical signal through indoor-space occur due to the turbulene. This fading often results in unacceptably large bit error probabilities and thus performance degradation of wireless optical communications. In this paper, when the spherical filter at the front-end of transmitter and receiver is used for wireless optical channel not satisfying line-of-sight, the signal-to-noise ratio as to zenithal angle and the effect from the turbulence due to indoor temperature are investigated.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.1
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• pp.40-47
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• 2013

By virtue of Rec. ITU-R P.1546 and geography information system, interference analysis for the fixed wireless system and radar has been presented based upon the frequency-distance rules with minimum coupling loss, and a comprehensive methodology for assessing interoperability between systems was examined in terms of received signal, protection ratio, frequency dependent rejection. Also to find the antenna gain from a discrimination angle, a useful S-I plane was introduced based on signal and interference vectors derived from the real map with geographic information. To show some computational results, geography information on the map was taken for the given area, and field strength and path profile were illustrated for the radar and fixed wireless system operating at 2.7 GHz, for convenience. In addition the interference effect of receiver was also checked as a function of radar beam direction including protection ratio and frequency dependent rejection. The developed interference analysis can be actually applied to evaluate interoperability for wireless systems in the VHF and UHF bands.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.113-116
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• 2015

This paper presented about the system for controlling a wireless power transmission using bluetooth protocol. Bluetooth protocol has been applied in many fields that communicate with data and audio signal in short range. Recently, however, Bluetooth low energy(BLE) more simple than the existing protocol is standardized and is widely used in medical applications and consumer electronics that handle small amount of sensor data and transmit by the low power control signal. It has also been adopted as the standard for the control in the wireless power transfer system. In this paper, We analysed and described the bluetooth low energy protocol techniques for controlling the wireless power transfer system.