Decision-directed digital phase locked loop

A decision-directed digital phase-locked loop, comprising:

• (a) instantaneous phase detecting means for obtaining an instantaneous phase digital value of a current zero cross point of a reproduced signal from a partial response channel based on a plurality of sampled values of said reproduced signal;
• (b) a digital loop filter for obtaining and outputting a phase value of a current data existing point of said reproduced signal in response to the instantaneous phase digital value obtained by said instantaneous phase detecting means;
• (c) phase value predicting means for obtaining a phase value of a future data existing point based on the phase value output by said digital loop filter of the current data existing point of said reproduced signal;
• (d) data predicting means for predicting future data of said reproduced signal based on the phase value of said future data existing point obtained by said phase value predicting means as well as on future sampled values of said reproduced signal;
• and
• (e) phase modification control means for determining, based on the future data predicted by said data predicting means, whether the current zero cross point of said reproduced signal is a data existing point, and for allowing said digital loop filter to modify the output phase value thereof using said instantaneous phase value when said current zero cross point is found to be a data existing point.