Wireless power transfer (WPT) or “wireless power” is the transmission of electrical energy from a power source transferred to an electrical load (such as an electric or electronic device) through-the-air and without the use of wires. Wireless power is a generic term that refers to a number of different power transmission technologies that transfers energy over a specific medium such as radio frequencies, coupled magnetic fields, and or other electromagnetic waves. In wireless power transfer, a wireless transmitter connected to a power source conveys the energy across an intervening space to one or more receivers, where it is then converted back to an electrical current and utilized by the host device. Wireless transmission is useful to charge or power electrical devices in cases where interconnecting wires are inconvenient, hazardous, or prohibitive.
Wireless power techniques fall into two general categories: The first is comprised of the more mature near field or “coupled” technology, which allows non-radiative transfer of energy over coupled magnetic fields and was originally pioneered by Nikola Tesla, more than 100 years ago.
The second and newer technology consists of far field or “uncoupled” energy transfer which includes radiative electromagnetic transmission such as radio frequency, light wave(s) and or ultrasonic vibration.