A method of determining the phases of a multitude of transmitting elements of an RF power generating unit, includes, in part, activating one of transmitting element during the first time period, turning off the remaining transmitting elements during the first time period, transmitting an RF signal from the activated transmitting element to a device to be charged during the first time period, detecting a first phase value associated with the RF signal at the device during the first time period, transmitting the detected first phase value from the device to the generating unit during the first time period, and adjusting the phase of the activated transmitting element in response to the detected first phase value.