Phase error compensation for improved timing recovery

Conventional disk drive channels typically adopt decision directed timing recovery, which is efficient when the excess bandwidth is negligible. The decision-directed phase detector estimates the timing phase error based on correlation between the ideally equalized signal samples and the observation samples. The ideal signal samples are constructed using past decisions. Decision errors due to a large sampling phase error limit the operating range of the timing recovery loop. In this paper, a phase error compensation technique is developed to allow the timing loop to operate on an increased range of phase error. Analyses show that for a threshold detector, the proposed technique increases the operating range by about 30% for the extended partial response class 4 (EPR4) channel without any added latency.