ASK Modulation & Demodulation System

A method comprising:

• detecting, at an output node of a wireless power receiver of a wireless charging system, an envelope voltage of a resonant capacitor of the wireless power receiver, the wireless power receiver comprising a receiving coil and the resonant capacitor connected in series, and a full-bridge rectifier;
• determining whether the envelope voltage at the output node is within a pre-determined voltage range;
• and
• when the envelope voltage is out of the pre-determined voltage range, controlling to adjust one or more parameters of the wireless power receiver based on the envelope voltage, in order for the envelope voltage at the output node of the wireless power receiver to fall within the pre-determined voltage range, the one or more parameters comprising a capacitance across the receiving coil and the resonant capacitor, or a current of a sub-circuit connected between the output node and a ground.