• Journal of IKEEE
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• v.23 no.1
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• pp.306-309
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• 2019

Wireless charging is a technology of transmitting power through an air gap to an electrical load for the purpose of energy dissemination. Compared to traditional charging with code, wireless power charging has many benefits of avoiding the hassle from connecting cables, rendering the design and fabrication of much smaller devices without the attachment of batteries, providing flexibility for devices, and enhancing energy efficiency, etc. A transmitting coil and a receiving coil for inductive coupling or magnetic resonant coupling methods are available for the near field techniques, but are not for the far field one. In this paper, the wireless power transfer (WPT) circuit by using magnetic resonant coupling method with a resonant frequency of 13.45 Mhz for the low power system is implemented to measure the power transmission efficiency in terms of mutual distance and omnidirectional angles of receiver.

• Journal of the Semiconductor & Display Technology
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• v.20 no.2
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• pp.29-33
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• 2021

A 5.8-GHz 1W wireless power transmission system was used for charging a smart phone. The voltage of one RF power receiver with antenna was not enough for charging. Several power receivers for charging a smart phone was connected serially. The voltage of several RF power receivers are highly enough for charging a smart phone within 50cm. However, the lack of current from small capacitances of RF-DC converters is not suitable for charging smart phone. It means very long charging time. In this paper, the voltage multiplier circuits for RF-DC converters were analyzed to increase the current and voltage at the same time to reduce the charging time in smartphone RF wireless charging. Through the analysis of multiplier circuits, the 7-stage parallel multiplier circuit with voltage-doubler units are suitable for charging the smartphone, which supplies 5V and 700mA at 3V@5.8GHz.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.562-568
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• 2013

This paper presents a design of a wireless power transfer system based on magnetic resonant coupling technology with in-band wireless communication. To increase the transmission distance and compensate for the change in the effective capacitance due to the varying distance, the proposed system used a loop antenna with a selectable capacitor array. Because the increased transmission distance enables multiple charging, we added a communication protocol operated at the same frequency band to manage a network and control power circuits. In order to achieve the efficient bandwidth in both power transfer mode and communication mode, the S-parameters of the loop antennas are adjusted by switching a series resistor. Our test results showed that the loop antenna achieved a high Q factor in power transfer mode and enough passband in communication mode.

• Proceedings of the KIEE Conference
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• summer
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• pp.1445-1447
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• 2004

In recent years, the smart card is widely applied for wireless communication, tracking, transportation logistics, diagnostic monitoring, access control and security. RF-ID system is universally applicable. Passive RF-ID system consists of reader and passive tag. The reader transmits energy and simple information to a tag by wireless and the power from the reader is transformed for controller, FRAM and Bluetooth module. In this paper, proposed for the improvement of wireless power transmission and demonstrated the propriety through experiments in several conditions.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.566-572
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• 2020

In a wireless power transmitter, the characteristics and effects of wireless power transmission between two induction coils are investigated, and a power converter circuit and a battery charger/discharger circuit using wireless power transmission technology are proposed. The advantage of wireless power transmitters and wireless chargers is that, instead of the existing plug-in-mounted wired charger (OBC; on-board charger), the user can wirelessly charge the battery without connecting the power source when charging power to the battery. There is. In addition, the advantage of wireless charging can bring about an energy efficiency improvement effect by using the secondary side rectifier circuit and the receiving coil, but the large-capacity long-distance wireless charging method has a limitation on the transmission distance, so many studies are currently being conducted. The purpose of the study is to study the transmitter circuit and receiver circuit of a wireless power transmission device using a primary coil, a secondary coil, and a half bridge series resonance converter, which can transmit power of a non-contact type power transmitter. As a result, a new topology was applied to improve the power transmission distance of the wireless charging system, and through an experiment according to each distance, the maximum efficiency (95.8%) was confirmed at an output of 3 kW at an 8 cm transmission distance.

• Korean Journal of Audiology
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• v.18 no.3
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• pp.105-111
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• 2014

Assistive listening devices (ALDs) refer to various types of amplification equipment designed to improve the communication of individuals with hard of hearing to enhance the accessibility to speech signal when individual hearing instruments are not sufficient. There are many types of ALDs to overcome a triangle of speech to noise ratio (SNR) problems, noise, distance, and reverberation. ALDs vary in their internal electronic mechanisms ranging from simple hard-wire microphone-amplifier units to more sophisticated broadcasting systems. They usually use microphones to capture an audio source and broadcast it wirelessly over a frequency modulation (FM), infra-red, induction loop, or other transmission techniques. The seven types of ALDs are introduced including hardwire devices, FM sound system, infra-red sound system, induction loop system, telephone listening devices, television, and alert/alarm system. Further development of digital wireless technology in hearing instruments will make possible direct communication with ALDs without any accessories in the near future. There are two technology solutions for digital wireless hearing instruments improving SNR and convenience. One is near-field magnetic induction combined with Bluetooth radio frequency (RF) transmission or proprietary RF transmission and the other is proprietary RF transmission alone. Recently launched digital wireless hearing aid applying this new technology can communicate from the hearing instrument to personal computer, phones, Wi-Fi, alert systems, and ALDs via iPhone, iPad, and iPod. However, it comes with its own iOS application offering a range of features but there is no option for Android users as of this moment.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.8 no.1
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• pp.11-17
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• 2008

Typical wireless sensor networks used in structural monitoring are continuous types wherein data transmission is progressive at all time that may include irrelevant and insignificant data and information. Continuous types of wireless monitoring systems often pose problems of handling large-sized data that may deteriorate the performance of the system. The proposed method is to suggest an event-triggered monitoring system that captures and transmits relevant data only. An error signal generated by the Principal Components Analysis (PCA) is utilized as an index for event detection and selective data transmission. With this new monitoring scheme, the remote server is relieved of unwanted data by receiving only relevant information from the wireless sensor networks. The performance of the proposed scheme was verified with simulation studies.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1357-1372
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• 2017

Energy harvesting techniques, particularly radio frequency energy harvesting (RF-EH) techniques, which are known to provide feasible solutions to enhance the performance of energy constrained wireless communication systems, have gained increasing attention. In this paper, we consider a wireless-powered cooperative communication network (WPCCN) for transferring energy in the downlink and forwarding signals in the uplink. The objective is to maximize the average transmission rate of the system, subject to the total network power constraint. We formulate such a problem as a form of wireless energy transmission based on resource allocation that searches for the joint subcarrier pairing and the time and power allocation, and this can be solved by using a dual approach. Simulation results show that the proposed joint optimal scheme can efficiently improve system performance with an increase in the number of subcarriers and relays.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12B
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• pp.1468-1473
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• 2011

With the proliferation of wireless LAN and smart phones, IP local broadcasting technology has been developed, and the new solution should be studied for error corrupted frames in the wireless broadcasting channel. In push service system using point-to-multi-point connection among broadcasting server and receivers, the technology proposed in this paper provides an effective data broadcasting system by employing frame length adjustment, redundant transmission, and repetitive transmission method.

• Speech Sciences
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• v.11 no.4
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• pp.67-73
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• 2004

Packet loss, jitter, and delay in the Internet are caused mainly by the shortage of network bandwidth. It is due to queuing and routing process in the intermediate nodes of the packet network. In the Internet whose bandwidth is changing very rapidly in time depending on the number of users and data traffic, controlling the peak transmission bit-rate of a VoIP. system depending on the channel condition could be very helpful for making use of the available network bandwidth. Adapting packet size to the channel condition can reduce packet loss to improve the speech quality. It has been shown in [1] that a VoIP system with an AMR speech codec provides better speech quality than VoIP systems with fixed rate speech codecs. With the adaptive codec mode assignment. algorithm proposed in [1], in this paper, we performed the voice transmission experiments using the wireless LAN through the real Internet environment. Experimental results are analyzed and discussed with our findings.