US Patent 9071289 Transceiver supporting multiple modulation schemes

The present application relates to a transceiver for use in a communications system that uses magnetic field induction to transmit data, the transceiver having an amplifier for driving an antenna, the amplifier forming, with a capacitance and a resistance connected in parallel with the antenna, a parallel resonant circuit. The resistance value of the resistance is adjustable, to permit adjustment of the loaded quality factor of the parallel resonant circuit. The transceiver includes a processing unit configured to determine the signal to noise ratio (SNR) of a signal received by the transceiver, and based on this SNR select a modulation scheme to apply to a data signal to be transmitted by the transceiver. The value of the resistance is adjusted to a level at which the loaded quality factor of the parallel resonant circuit is able to support the bandwidth and data rate required by the selected modulation scheme.