The disclosure features wireless power transmitters configured to detect a radio frequency identification (RFID) tag, the transmitters including a transmitter resonator, a transmitter impedance matching network coupled to the transmitter resonator, an amplifier coupled to the transmitter impedance matching network, a detection subsystem connected to the transmitter resonator, and a controller coupled to the amplifier and to the detection subsystem and configured so that during operation of the transmitter, the controller is configured to control the transmitter resonator, the amplifier, and the impedance matching network to cycle the transmitter between a power transmission mode and a RFID tag detection mode.