As the interest in wireless power transmission (WPT) grows, the research and development of a wireless charging system that can be applied to real life have been in progress. WPT is implemented in three methods. One is way through magnetic induction. This method involves transmitting power through the current generated in two coils. It is used for the electric toothbrushes and electric shavers, and it is also fabricated as a wireless vehicle charger of prototype. If the arrays of transmitting and receiving coils do not match, however, the efficiency will decrease rapidly, and the transmission distance will be shortened. The second WPT method is way through microwave. This method involves transferring energy to radiate the electromagnetic wave of high frequency in the air. As long-distance transmission is possible through this method, it is being studied as a technology for renewable-energy-source applications such as power transmission and space-solar power satellites. Due to the use of a high frequency, however, the transmission efficiency is influenced by the surrounding environment, and the method is harmful to the human body. The last WPT method is way through magnetic resonance. It overcomes the disadvantages of the magnetic-induction and microwave methods and can transfer power within a few meters. Also, the power-transfer does not affect the environment because it uses a low frequency. In this method, however, it is difficult to reduce the size of the transmitting and receiving coils with a high Q-factor, and how to improve the efficiency to enable it to transmit power beyond a few meters has yet to be studied.
In this paper, we analyzed the transmission characteristics of WPT system using a superconducting resonant coil. WPT of magnetic resonance was implemented at a frequency of 12MHz. The superconducting coil was applied for resonance. A resonance coil was wound 8.5 times using a superconductor with a 300 mm diameter. For comparison, a resonance coil was designed using a copper coil. In order to analyze the transmission characteristics, the simulation was performed using the high frequency structure Simulator (HFSS). We analyzed the transmission characteristics through experiments using network analyzer. As a result of the simulation, the S11 values of the superconductor and copper were respectively -8.7dB, -23.1dB and the resonance frequency was 9,6MHz. S11 the value of the superconductor and copper in the experimental was respectively -9.1dB, -21.65dB and resonance frequency was 12MHz. Through simulations and experiments, the transmission efficiencies of the superconducting resonance coil were confirmed higher than that of the copper resonance coil.