Patent ID: 8294513

Claim:
A demodulator that demodulates a plurality of received symbols having different amplitude in a carrier wave, the demodulator comprising: an amplitude value calculation unit that calculates a received symbol amplitude value by adding an absolute value of an in-phase component and an absolute value of quadrature component determined from an amplitude of the carrier wave in the received symbol; and a demodulation unit that detects a change of the received symbol amplitude value calculated by the amplitude value calculation unit, and demodulates the received symbol based on the detection result, wherein the demodulation unit sets a first threshold between a maximum received symbol amplitude value of a first received symbol output from the amplitude value calculation unit and a maximum received symbol amplitude value of a second received symbol smaller than the maximum received symbol amplitude value of the first received symbol, sets a second threshold between a minimum received symbol amplitude value of the first received symbol and a minimum received symbol amplitude of the second received symbol smaller than the minimum received symbol amplitude value of the first received symbol, and demodulates the received symbol based on a comparison result of the received symbol amplitude value output from the amplitude value calculation unit with the first and the second thresholds.