A wireless power receiver receives electrical power via electromagnetic field coupling from a wireless power transmitter. During communication time periods, the power receiver alters the electromagnetic field in a manner that the power transmitter can detect as a string of logic bits in a communication bit stream for sending data to the power transmitter. During pause time periods when data is not being sent to the power transmitter, the power receiver alters the electromagnetic field in a manner that the power transmitter does not detect as a string of logic bits (e.g. at a rate outside a communication frequency band). In some embodiments, a ripple is reduced in a voltage produced by the wireless power receiver from the electromagnetic field during the communication and pause time periods.