Patent ID: 6515818
Filing Date: 2003-02-04
Classification: G11B

Abstract:
In a disk drive having a servo control unit for controlling a position of a read/write head with respect to odd and even tracks written to a disk with servo bursts designated as A, B, C, and D in a quadrature A B C D pattern, such that when said head is positioned over the half-track of one of said odd and even tracks, approximately one-half of the amplitude of the A and B bursts will be read and when said head is positioned over the half-track of the other of said odd or even tracks, approximately one-half of the amplitude of the C and D bursts will be read, a method of performing track follow at quarter track positions, comprising:reading, with said read/write head, said servo bursts located on said disk; deriving a position error signal from amplitudes of said servo bursts; positioning said read/write head over said quarter track position in accordance with said position error signal; and wherein said step of deriving a position error signal from amplitudes of said servo bursts comprises: determining one of Câˆ’A and Dâˆ’B when track following at âˆ’Â¼ track positions; and determining one of Aâˆ’D and Bâˆ’C when track following at +Â¼ track positions.