receivers (Rxs) is shown as overview in Fig. 5. The system is
designed to charge mobile phones with a large freedom of
movement to realize an easy and user-friendly wireless
charging when users are interacting with a phone or leave the
phone on a specific surface. An AC-DC converter supplied by
the US grid is designed to provide a constant voltage to DCAC
amplifier. The amplifier is able to generate a signal with a
frequency of around 6.78 MHz to pro vide the resonator,
which is made up by a Tx coil and an impedance matching
network. A secondary impedance matching network, a
rectifier and a DC-DC converter are connected to a Rx coil to
charge a phone with a constant 5 V power supply.