In an example, an integrated circuit includes a communication and control unit. The communication and control unit controls an inverter that applies an alternating current output signal to a transmission coil for reception by a receiver. The communication and control unit causes the inverter to provide a first and second transmit powers to the transmission coil, and the communication unit receives a first and second power received signals from the receiver in response to the first and second transmit powers. The communication and control unit determines a first gain and offset using the first transmit power, the first power. When a third transmit power greater than the second transmit power is transmitted by the transmission coil, the communication and control unit determines a second gain and a second offset using the first transmit power, the first power received signal, the third transmit power and a third power received signal.