A system, a circuit, and a method of wireless power transfer using a transmitter and a controller coupled to the transmitter. The controller is configured to perform operations including causing the transmitter to scan a frequency range that includes a maximum frequency and a minimum frequency. The operations further include determining one or more detections based at least on the scan of the frequency range. The detection may include a presence of one or more receivers, an absence of one or more receivers, and/or a presence of a foreign object. The operations include determining one or more further operations based on the one or more detections.