System and method for compensating for radial incoherence associated with reading servo sectors

A system for compensating radial incoherence while reading servo data from a rotating storage medium, the system comprising:

• an equalizer comprising a filter and a plurality of phase rotators, wherein the filter is to (i) receive a digital signal comprising a bit sequence of the servo data read from the rotating storage medium, and (ii) filter the digital signal, and wherein at least some of the plurality of phase rotators are to phase rotate an output of the filter to provide a respective one of a plurality of phase rotated signals;
• a Viterbi detector to operate based on a trellis state machine, wherein the trellis state machine comprises a plurality of main branches, wherein each of the plurality of main branches comprises a plurality of sub-branches, wherein each of the plurality of main branches is to receive the plurality of phase rotated signals respectively at corresponding ones of the plurality of sub-branches, and wherein the Viterbi detector is to (i) determine branch metrics for each of the sub-branches, (ii) determine a minimum branch metric among all the branch metrics of the plurality of sub-branches for each of the plurality of main branches, and (iii) process the minimum branch metric as a representative of a corresponding branch using an add-compare-select process of the Viterbi detector to determine a most likely received bit sequence;
• and
• a servo control module to adjust a location of a read/write head of the rotating storage medium based on the most likely received bit sequence.

A method for compensating radial incoherence while reading servo data from a rotating storage medium, the method comprising:

• receiving a digital signal comprising a bit sequence of the servo data read from the rotating storage medium;
• equalizing the digital signal via at least one filter;
• rotating the digital signal or at least one output of the at least one filter to generate a plurality of phase rotated signals, wherein the plurality of phase rotated signals are generated concurrently;
• receiving at each of a plurality of main branches of a Viterbi detector the plurality of phase rotated signals, wherein the Viterbi detector is to operate based on a trellis states machine, wherein the trellis state machine comprises the plurality of main branches, each of the plurality of main branches comprises a plurality of sub-branches, and wherein the plurality of phase rotated signals are received respectively at corresponding ones of the plurality of sub-branches,
• determining branch metrics for each of the sub-branches;
• determining a minimum branch metric among all the branch metrics of the plurality of sub-branches for each of the plurality of main branches;
• processing the minimum branch metric as a representative of a corresponding branch using an add-compare-select process of the Viterbi detector to determine a most likely received bit sequence;
• and
• adjusting a location of a read/write head of the rotating storage medium based on the most likely received bit sequence.