Patent ID: 8027111

Claim:
A word synchronization apparatus for detecting L-bit sync words occurring at N-bit intervals in a pulse-position-modulation encoded (PPM-encoded) servo pattern read signal read from magnetic tape in a tape drive, the apparatus comprising: a soft output detector for processing the PPM-encoded servo pattern read signal to produce a series of soft output samples corresponding to respective bits encoded in the servo pattern; and a sync word detector for producing block correlation values for respective positions of a sliding L-sample block in the series of soft output samples by calculating, at each block position, bit correlation values indicating correlation between respective samples and corresponding bits of the sync word, and summing each bit correlation value minus a predetermined function of the corresponding sample value; wherein the sync word detector is adapted to detect a sync word at the block position with the maximum block correlation value in an (N+L−1)-sample sequence of the series of soft output samples.