• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.468-479
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• 2016

In order to supply power to online monitoring systems that are attached to high voltage catenary or overhead wires, a wireless power transfer system is required that is able to transmit power over the insulation gap. Such wireless power transfer systems have transmitter and receiver coils that have diameters of over 10cm. This paper focused on an investigation of the sources of loss in the coils when the coils are fabricated using printed circuit board technology. Using finite element simulation results, it has been shown that the dielectric loss in the substrate was the dominant source of the total loss. It has been demonstrated that the selection of a proper dielectric material was the most critical factor in reducing the loss. For further reduction of the loss, the distributed tuning capacitor method and the slotting of the inter-turn spaces have been proposed. For the evaluation of the proposed methods, four coils have been fabricated and their equivalent series resistances and quality factors were measured. Measured quality factors were greater than 300, which means that these devices will be helpful in achieving high coil-to-coil efficiency.

• 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.

• Journal of electromagnetic engineering and science
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• v.18 no.3
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• pp.145-153
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• 2018

In this paper, the efficiency of single-input multiple-output (SIMO) wireless power transfer systems is examined. Closed-form solutions for the receiver loads that maximize either the total efficiency or the efficiency for a specific receiver are derived. They are validated with the solutions obtained using genetic algorithm (GA) optimization. The optimum load values required to maximize the total efficiency are found to be identical for all the receivers. Alternatively, the loads of receivers can be adjusted to deliver power selectively to a receiver of interest. The total efficiency is not significantly affected by this selective power distribution. A SIMO system is fabricated and tested; the measured efficiency matches closely with the efficiency obtained from the theory.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.7
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• pp.910-915
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• 2014

Recently, wireless power transfer (WPT) system is widely studied. WPT system is very attractive because it removes power cables from home appliances, office equipment and battery chargers for electric vehicle. However, pickup's posture affects the performance greatly. In this paper a new pickup system whose output voltage is less sensitive to its posture is proposed. The proposed pickup system is composed of three coils perpendicular to each other. A prototype is constructed and tested, and its usefulness is verified.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.4
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• pp.286-289
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• 2018

This paper tests the feasibility of using the transparent electrode as the electrode of the capacitor in order to use the vehicle glass of the electric vehicle for a capacitive coupling wireless transfer (CCWPT). Large coupling capacitance can be obtained due to large area and high permittivity using the glasses of an electric vehicle. However, if an electrode is formed on a metal such as copper, then a view cannot be guaranteed and a transparent electrode can pose a solution. Therefore, the coupling capacitor is implemented by forming a glass dielectric with an ITO transparent electrode on one side through a semiconductor deposition process. The loss of the coupling capacitor is investigated, and a 200 W CCWPT prototype is fabricated and tested for its characteristics and power transfer.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.62-63
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• 2011

The wireless power transfer system using electromagnetic resonance is consists of PFC circuit, LLC resonant converter, high frequency DC-AC inverter and ECR devices for wirelessly transmitting the power. The output voltage of the module with free input voltage is 1MHz, 230Vp-p. As a experimental result, the wireless power transmission is confirmed and it is varified the validity of the experiment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.6
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• pp.1238-1240
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• 2009

In the wireless sensor network, cooperative transmission is an effective technique to combat multi-path fading and reduce transmitted power. Relay selection and power allocation are important technical issues to determine the performance of cooperative transmission. In this paper, we proposed a new multi-relay selection and power allocation algorithm to increase network lifetime. The proposed relay selection scheme minimizes the transmitted power and increase the network lifetime by considering residual power as well as channel conditions. Simulation results show that proposed algorithm obtains much longer network lifetime than the conventional algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.64-69
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• 2009

In this paper, we evaluate a performance on a transmission power control algorithm in a SIR-based wireless networks. We consider the existing iterative power control algorithms into a unified dynamic state system formulation in both continuous-time and discrete-time system. Numerical experiments are performed under the disturbance of sinusoidal. These results indicate that the proposed power control scheme has a performance improvement with a better disturbance elimination in wireless mobile systems.

• Journal of Industrial Technology
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• v.29 no.B
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• pp.145-149
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• 2009

A RF-DC converter is one of the most important components for a wireless power transmission. It has been developed for many applications such as space solar power system, and Radio Frequency Identification(RFID). In this paper, we designed three types of RF-DC converter and compare the performance of each. All types RF-DC convertoer have a maximum conversion efficiency at input power level of 0 dBm~5 dBm and RF-DC converter of third type was the best performance that has a 21.9% of conversion efficiency.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.414-415
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• 2008

In this paper, we consider the development methodology of wireless monitoring system for a distribution transformer. The master/ slave devices are installed in the power distribution feeder and measure the current state of pole or ground transformers. After measuring, the devices send the measurement data to operating room through the wireless network such as RF and CDMA so that the power distribution supervisor can prevent a distribution transformer damaging caused by overloads and imbalance of loads.