Table 2.

Power transmission characteristics [58].

Features	Resonant Coupling	Inductive Coupling	Far-Field Transfer
Field	Resonance	Magnetic method	Electromagnetic
Scheme	Resonator	Coil	Antenna
Efficiency	High	High	Low to high
Distance	Medium	Short	Short to long
Frequency	KHz to MHz	KHz to MHz	GHz
Power	High	High	Low to high
Typical load	Fixed impedance	Varying impedance	Fixed impedance
Regulation	Under discussion	Under discussion	Radio wave
Pros	Medium efficiency in a short distance	High efficiency	Long distance
Cons	Difficulties in preserving high Q	Very short distance	Low efficiency and safety issues