MODULATED SIGNAL DETECTING APPARATUS AND MODULATED SIGNAL DETECTING METHOD

A phase difference error detecting unit (8) detects a phase difference error component included in a phase difference component; a phase difference correcting unit (3) corrects a first signal having the phase difference component as an angle of a cosine function and a second signal whose angle of the cosine function differs from that of the first signal by approximately À/2 based on the detected phase difference error component; a phase operating unit (6) operates a phase difference component from the first signal and the second signal corrected by the phase difference correcting unit (3); and the phase difference correcting unit (6) obtains the corrected first signal and the corrected second signal by rotating a coordinate point represented by the first signal and the second signal on a polar coordinate plane by an angle corresponding to the phase difference error component.