HF near-field power transfer and communications using antiparallel loops

Abstract

Inductively wireless power transfer is used in various applications to charge products including, but not limited to, electric-powered transportation carts, power tools, and cooking appliances. In particular, wireless power chargers for portable electronic devices, such as mobile phones, personal digital assistants (PDAs), or E-readers, have recently entered the market. This can enhance the convenience of charging portable devices without any cumbersome power cord. Although inductively coupled WPT has high efficiency, the spacing between the transmitting and receiving antennas must be very close. To solve this problem, the mid-range WPT technology with a spatial freedom has been required. For efficient non-radiative mid-range WPT, the resonant coupling method which uses resonant transmitting and receiving antennas is being developed. The transfer efficiency of WPT using the resonant coupling method is sensitive to various conditions including a receiving antenna at different operating distances, close proximity of a metallic object, or multiple receiving devices because it is difficult to maintain a high Q-factor. Although several techniques such as automatic impedance matching circuit, frequency tracking, and metamaterials have been studied to obtain the stable efficiency of WPT in the near-field, impedance mismatch has still been a problem when a receiving antenna has been placed at the different operating distance with regard to the transmitting antenna. In this dissertation, the antiparallel loop for the near-field power transfer and communications has been proposed. The first aim is to theoretically analyze the mutual inductance between the transmitting and receiving antennas using a magnetic coupling and the corresponding transfer efficiency with regard to the different operating distance in the near-field. Furthermore, the theoretical analysis related to the loaded Q-factor between the transmitting and receiving antennas in the near-field data co...