Antenna Characterization for Wireless Power-Transmission System Using Near-Field Coupling

A fundamental study was focused on the investigation of wireless power transmission by near-field coupling from the view point of the antennas. Two types of antennas - dipole and loop antennas - were used as the transmitting antenna and the receiving antenna for electrical near-field coupling and for magnetic near-field coupling, respectively. The relationships among the power-transmission efficiency and the antennas´ geometries, the antennas´ electrical sizes, the impedance matching of the antennas, and the ohmic losses in the antennas and the impedance-matching circuits were clarified. Several observations were obtained, demonstrating the influence on the power-transmission efficiency of the impedance matching and ohmic losses in the wireless power-transmission system associated with near-field coupling.