• International Journal of Internet, Broadcasting and Communication
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• v.13 no.3
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• pp.25-33
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• 2021

Energy-harvesting wireless sensor networks(EH-WSNs) can collect energy from the environment and overcome the technical limitations of existing power. Since the transmission distance in a wireless sensor network is limited, the data are delivered to the destination node through multi-hop routing. In EH-WSNs, the routing protocol should consider the power situations of nodes, which is determined by the remaining power and energy-harvesting rate. In addition, in applications such as environmental monitoring, when there are urgent data, the routing protocol should be able to transmit it stably and quickly. This paper proposes an adaptive routing protocol that satisfies different requirements of normal and urgent data. To extend network lifetime, the proposed routing protocol reduces power imbalance for normal data and also minimizes transmission latency by controlling the transmission power for urgent data. Simulation results show that the proposed adaptive routing can improve network lifetime by mitigating the power imbalance and greatly reduce the transmission delay of urgent data.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.102-107
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• 2021

In this paper, the measurements of received power was shown and compared in two developed 5.8GHz 25W wireless charging systems. One is the system using commercial transmission antenna, and the other is the system using transmission antenna combined with metamaterial. The system combined with metamaterial shows higher received power due to negative reflective index of metamaterial. In addition, a comparative analysis of the systems shows that the transmission efficiency in the systems can decrease the real gain of transmission antenna due to higher side robe of beam pattern. The side robe beams of transmitting antenna interferes transmitted beam with the reflected beams from the bottom region due to the side robes. The failure problems of the RF wireless charging systems are discussed and proposed in order to charge mobile devices through the RF wireless charging system.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.21-24
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• 2019

In this paper, 5.8GHz 25W microwave wireless power transmission system was developed. The transmission system is composed of a signal generator, a 1W drive amplifier, a 25W power amplifier, and a circularly polarized transmission antenna. The receiving system was fabricated with an integrated receiver that combines a circularly polarized receiving antenna, a pass band filter, and an RF-DC converter. And a multi-integrated receiver had twelve parts, including an integrated receiver. Under the conditions, voltage and current were measured for the system at 5cm intervals from a minimum distance of 5cm to a maximum distance of 80cm. The power was calculated for the system. The results of the system are shown in tables and graphs. The power decreases with distance, but the power does not drop sharply due to a multi-integrated receiver.

• Journal of IKEEE
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• v.21 no.3
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• pp.195-201
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• 2017

High-power wireless transmission system becomes a key technology for the advance of battery-powered devices. The wireless power transfer devices are currently dominated by the inductive and capacitive wireless power transfer systems, which have relatively low power transmission capacity and low efficiency rather than the wired power transmission. The work presented in this paper proposes an alternative method of high-power transmission system, based on a variable speed motor system with a magnetic coupling. It enables high-capacity power transmission, high efficiency, and low possibility of failures, and the performance of the proposed scheme is verified by simulation and experiments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.925-928
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• 2013

In this paper, we propose a relay-based wireless power transmission scheme in order to solve the problems of an existing wired power transmission for energy harvesting system. The proposed scheme can be transferred electromagnetic induction-based wireless power transmission by placing a 4-way coils in the energy block. We confirm the reliability of the electricity transmission through the relay control algorithm. Consequently, the proposed scheme can extend the transmit receive paths of transmission power.

• Journal of Power Electronics
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• v.19 no.1
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• pp.211-219
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• 2019

In magnetically coupled resonant (MCR) wireless power transfer (WPT) systems, the introduction of additional intermediate coils is an effective means of improving transmission characteristics, including output power and transmission efficiency, when the transmission distance is increased. However, the position of intermediate coils in practice influences system performance significantly. In this research, a three-coil MCR WPT system is adopted as an exemplification for determining how the spatial position of coils affects transmission characteristics. With use of the fundamental harmonic analysis method, an equivalent circuit model of the system is built to reveal the relationship between the output power, the transmission efficiency, and the spatial scales, including the axial, lateral, and angular misalignments of the intermediate and receiving coils. Three cases of transmission characteristics versus different spatial scales are evaluated. Results indicate that the system can achieve relatively stable transmission characteristics with deliberate adjustments in the position of the intermediate and receiving coils. A prototype of the three-coil MCR WPT system is built and analyzed, and the experimental results are consistent with those of the theoretical analysis.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.437-441
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• 2012

In this paper, we have designed and manufactured 10MHz power source for the application of short distance wireless power transmission. The designed power source consists of a DDS(direct digital synthesizer) signal generator, a buffer driver and a balanced power amplifier. Short range wireless power transmission is usually carried out by near-field inductive coupling between source and load. The distance variation between source and load gives rise to the change of load impedance of power amplifier, which has effect on the operation of power amplifier. To overcome this problem due to load variation of power amplifier, we have adopted the balanced power amplifier using the quadrature hybrid implemented by lumped capacitors and a mutually coupled coil. The experiment results show the above 40dBm output power, frequency range of 9 to 11MHz, and total DC power consumption of 36W.

• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.88-91
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• 2015

Wireless power transmission (WPT) is a technology using free space as a conductor for transmitting electric power, which aims to transfer not just the transmission signal but also the electrical energy itself. This paper takes issue with the microwave wireless transmission technology utilizing in long-distance transmission. To construct the WPT system, several components are needed, such as RF Oscillator which converts AC power to RF through DC status, high gain antenna and RF rectifier that converts RF back to DC. The array topology is good a candidate for wide use. The objective of this research is to study the efect of the WPT systmem on electric power system.

• Journal of IKEEE
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• v.22 no.1
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• pp.216-222
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• 2018

Long-range wireless power transmission technology goes beyond mere cell phones and small appliances, and is the core technology of 4'th industrial revolution such as robot, electric car, and IoT sensor network. In this paper, we will explore the evolution of long-range wireless power transmission technologies that have already become commercially available, with rapid advances in technology, beyond the traditional short-range technology that has become technologically common. Through this, it is intended to check the domestic research level and progress by identifying core technologies and technical challenge.

• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.676-682
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• 2011

Sybil attack can disrupt proper operations of wireless sensor network by forging its sensor node to multiple identities. To protect the sensor network from such an attack, a number of countermeasure methods based on RSSI (Received Signal Strength Indicator) and LQI (Link Quality Indicator) have been proposed. However, previous works on the Sybil attack detection do not consider the fact that Sybil nodes can change their RSSI and LQI strength for their malicious purposes. In this paper, we present a Sybil attack detection method based on a transmission power range. Our proposed method initially measures range of RSSI and LQI from sensor nodes, and then set the minimum, maximum and average RSSI and LQI strength value. After initialization, monitoring nodes request that each sensor node transmits data with different transmission power strengths. If the value measured by monitoring node is out of the range in transmission power strengths, the node is considered as a malicious node.