Table 12.

Summary of WPT regimes.

WPT regime	Technology	Types of RF wave	Frequency	Transfer dis tance in aira)	Attenuation in tissue	Transfer distance through tissuea)	Directivity[468]	Receiver	Common target location
	Inductive coupling	Magnetic field	Hz–MHz	Short	Low	Short	Low	Coil	Subcutaneous space
Near-field	Capacitive coupling	Electric field	Hz–MHz	Short	Low	Short	Low	Metal plate electrode	Subcutaneous space
Mid-field		Electromagnetic radiation	MHz–GHz	Mid–long	Mid	Mid–long	Mid	Antenna (dipole, monopole, etc.)	Deep implant location (GI tract, brain, heart, etc.)
Far-field		Electromagnetic radiation	>GHz	Long	High	Short	High	Antenna (dipole, monopole, etc.)	Eyes

^a)Definition of distance range: short (distance < a wavelength & distance < size of transmitter), Mid (distance < a wavelength & distance < 10 × size of transmitter), and long (distance > a wavelength).^[469]