In one aspect, an apparatus for wirelessly transmitting power to a wireless power receiver comprises a transmitter circuit configured to transmit wireless power via a magnetic field at a first frequency and a second frequency, the second frequency different than the first frequency and is an integer multiple of the first frequency. The apparatus further includes a processor circuit configured to detect a presence of multiple wireless power receivers each being capable of receiving power via the magnetic field over at least one of the first and second frequency and further configured to identify frequency charging capabilities of each of the detected wireless power receivers. The transmitter circuit further configured to concurrently transmit wireless power to first and second wireless power receivers at the first frequency and the second frequency, respectively, based on the respective charging capabilities of the first and second wireless power receivers.
