Investigation of near-field wireless power transfer between two efficient electrically small planar antennas

In this paper, an approximate 50 Ω input impedance and high efficient electrically small planar antenna (named ant1) for near-field wireless power transfer is proposed. The power transfer efficiency and resonant frequency characteristic of a wireless power transfer system, according to different separation distances and orientations between transmitting antenna and receiving antenna, are analyzed and compared. In addition, power transfer efficiency of wireless power transfer systems are investigated using proposed low radiation loss antenna (named ant2) and high dielectric loss antenna (named ant3). It is found that the power transfer system composed of proposed ant1 can achieve an effective power transfer efficiency both in coupled mode region and radiating near-field region without simultaneous conjugate matching at feeding port of the transmitting antenna.