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US 6,115,198 AGranted
PR4 sampled amplitude read channel for detecting user data and embedded servo data
AssigneeCirrus Logic, Inc.
InventorsDavid E. Reed, William G. Bliss
Life of this patent
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AssigneeCirrus Logic, Inc.
InventorsDavid E. Reed, William G. Bliss
Estimating the term…
A partial response class-IV (PR4) sampled amplitude read channel is disclosed for detecting user data and embedded servo data. The detected servo data is encoded using a novel servo code capable of accurately decoding detected codewords representing servo track address during seek operations, even when the recording head flies between two adjacent tracks, and capable of correcting errors in the detected codedwords caused by noise in the read signal, such as inter-symbol interference. In one embodiment, the servo code corrects certain minimum distance error events, such as a bit shift error event, associated with a trellis type sequence detector. To achieve the equivalent effect of a conventional Gray code, the codewords are arranged such that adjacent track addresses differ by a number of bits relative to the minimum distance error events corrected. In this manner, when the recording head spans two adjacent tracks during a seek operation, the ambiguity in the detected codeword will be resolved in favor of one of the adjacent track addresses. To further increase performance, the servo data PR4 sample values are converted into an EPR4 response and detected with a sliding threshold detector. This modification provides the same performance gain as a PR4 sequence detector matched to a d=1 constraint, but at less cost. One of the PR4 sliding threshold detectors for detecting user data can be advantageously shared to detect the servo data-the only additional hardware required is a 1+D filter for converting the PR4 samples of the servo data to EPR4 samples.
A sampled amplitude read channel for reading user data and servo data recorded on a disk storage medium by detecting an estimated data sequence from discrete time sample values generated by sampling an analog read signal emanating from a read head positioned over the disk storage medium, comprising:
A sampled amplitude read channel for reading user data and servo data recorded on a disk storage medium by detecting an estimated data sequence from discrete time sample values generated by sampling an analog read signal emanating from a read head positioned over the disk storage medium, comprising:
A sampled amplitude read channel for reading user data and servo data recorded on a disk storage medium by detecting an estimated data sequence from discrete time sample values generated by sampling an analog read signal emanating from a read head positioned over the disk storage medium, comprising:
Dependencies are inferred from the claim text.