Method and apparatus for demodulating a servo burst signal in a hard disk drive

摘要

A hard disk drive system (10) includes a read head (21) for reading information from a rotating magnetic disk (12). The read head outputs a servo burst signal in response to servo information (59) on the disk. An analog-to-digital converter (33) is provided to oversample the servo burst signal during each of a plurality of successive time intervals, in order to obtain a plurality of samples for each such time interval. An accumulator (74) is provided to sum the samples for each time interval, in order to obtain for each time interval a respective accumulation value that represents an integration of the burst signal for that time interval. A filtering circuit (86) is provided to determine a burst value for the servo burst signal, by applying a filtering function to a set of the accumulation values. The filtering function may involve determining a median accumulation value from the set of accumulation values, or determining a mean of the accumulation values in the set.