**3. Wireless power transfer (WPT)**

Wireless Power Transfer Systems (WPT) can be classified as far- and near-field WPT systems. The WPT system in far field is divided into LASER, photoelectrical, RF and microwave whereas the inductive, magnetic and capacitive coupling methods are classified as the near-field. WPT is the main alternative to powerimplantable devices by inductive connection and resonant connection [10]. The method is based on an antennas delivering RF power to a charging device. The wireless power transfer approaches are shown in **Figure 1**.

**Figure 1.** *The wireless power transfer methods [10].*
