In principle, the distance of wireless power transfer (WPT) via radio waves from a transmitting antenna to a receiving one can be extended if the medium of wave propagation is lossless, e.g., vacuum in space. Technically, the distance limitation of WPT via radio waves is dominated by the power required by users as well as the limitation of system size and efficiency in practical applications. It is easy to develop multiuser WPT systems using WPT via radio waves because they are electromagnetically uncoupled and no interference between circuit parameters at a transmitter occurs even with increasing number of users. Besides, since the beam efficiency between a transmitting antenna and a receiving one is not high, multiuser WPT systems are also suitable when WPT systems via radio waves are applied in far field.

Chapter Contents:

• 11.1 Introduction
• 11.2 Long-distance WPT in far field
• 11.2.1 Energy harvesting and scavenging
• 11.2.2 Ubiquitous WPT
• 11.3 Long-distance WPT in the radiative near field
• 11.4 Long-distance WPT in fielded field
• 11.5 Near-field WPT in a cavity resonator
• References

Inspec keywords: radiowave propagation; receiving antennas; transmitting antennas; inductive power transmission; radiofrequency power transmission

Other keywords: WPT system; long-distance wireless power transfer; radio waves; transmitting antenna; system size; receiving antenna; wave propagation

Subjects: Single antennas; Radiowave propagation; Wireless power transmission