ASK Modulation & Demodulation System

In an embodiment method, an envelope voltage of a resonant capacitor of a wireless power receiver in a wireless charging system may be detected at an output node. One or more parameters of the wireless power receiver may be adjusted in order keep the envelope voltage within a pre-determined voltage range. The one or more parameters includes a capacitance across a receiving coil and the resonant capacitor, or a current of a sub-circuit connected between the output node and a ground. An amplitude shift keying (ASK) carrier signal may be detected at a wireless power transmitter of the wireless charging system and attenuated. A demodulated ASK signal may be generated from the attenuated ASK carrier signal based on peak values of the attenuated ASK carrier signal and a zero-crossing signal generated from the attenuated ASK carrier signal.