| 摘要 |
Methods and apparatus for detecting L-bit sync words occurring at N-bit intervals in PPM-encoded servo pattern read signals read in magnetic tape drives. A soft output detector processes the PPM-encoded servo pattern read signal to produce a series of soft output samples corresponding to respective bits encoded in the servo pattern. A sync word detector then produces block correlation values for respective positions of a sliding L-sample block in the series of soft output samples by (i) calculating at each block position bit correlation values indicating correlation between respective samples and corresponding bits of the sync word and (ii) summing each bit correlation value minus a predetermined function of the corresponding sample value. The sync word detector then detects 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. |
