Methods and circuitry for calibrating inductive-capacitive resonant circuits are disclosed. An example of the circuitry includes an inductive-capacitive (L-C) resonant circuit operable to receive signals in response to induced electromagnetic signals transmitted on a carrier frequency. A demodulator has a signal source and is operable to demodulate signals generated by the L-C resonant circuit. Switching circuitry is operable to inject signals generated by the signal source into the L-C resonant circuit during a calibration mode. The calibration mode is for adjusting the capacitance in the L-C resonant circuit to tune the L-C resonant circuit to the carrier frequency.