Patent ID: 6943970

Claim:
A position demodulating method of a disk apparatus, for calculating a decoded position after position signals of a disk read by a head were demodulated, comprising: a first step wherein after position information of different phases are demodulated from said position signals, they are multiplied by a position sensitivity gain, respectively, and first position information PosN and second position information PosQ are calculated; a second step wherein said first position information PosN and said second position information PosQ are compared and third position information Pos 1 and fourth position information Pos 2 in which influences of an error of the position sensitivity gain appear oppositely are calculated; and a third step wherein a first weight gain G 1 and a second weight gain G 2 are obtained from said third position information Pos 1 and said decoded position is calculated by including an addition value of a multiplication value obtained by multiplying said third position information by said first weight gain and a multiplication value obtained by multiplying said fourth position information by said second weight gain; wherein said first weight gain is a segment primary function which changes like a triangle for a detected position so as to be equal to 1 at a track center and 0 at track boundary positions on both sides.