Partial-response maximum-likelihood

Abstract: Synchronous detection of fine position servo information within a partial response maximum likelihood (PRML) data channel Servo information (17) is recorded as a pair or series of fractional-track-width sinewave concurrent burst patterns producing an on-track phase generating a position error signal varying linearly about track centerline and at least one off-track phase generating a position error signal related to track boundary Head (26) generates on-track phase and off-track phase analog signals that are gain normalized (40) and synchronously quantized (46) Mulfiplying by a normalization factor from a correlation signal generator (64) during servo sampling intervals provides normalized samples, integrating (66) on-track phase normalized samples provides on-track position error signal (82), and integrating (66) off-track phase normalized samples provides an off-track position error signal (88) A discrete matched filter is also used

Abstract: A serializer/deserializer encoder-decoder for a disk drive achieves increased storage capacity through the use of partial response maximum likelihood class IV (PRML-IV) coding. Reduction of hardware requirements is realized by the integration of similar read and write mode functions into common circuit elements in order to reduce duplication. To this end, a data word selector selectively receives or sends data words in the write/read mode, respectively, from a data sequencer. Dependent upon the mode the data words are either provided to an encoder or received from a decoder for translation to/from code words. The encoder-decoder sends or receives the code words to a code word selector which in turn connects with the serializer-deserializer for coupling with the write or read channel.

Abstract: A method and apparatus are provided for controlling a digital filter function included in a data path within gain and timing control loops of a PRML magnetic recording channel. The digital filter function is removed from the data path during an acquisition mode and the digital filter function is restored to the data path during a tracking mode. A predetermined gain and a quantized delay at a synchronization frequency are provided when switching from acquisition mode to tracking mode. A unity gain and a delay of an integer number of sample periods are provided at a synchronization frequency when switching from acquisition mode to tracking mode.

Abstract: A partial response maximum likelihood (PRML) data detecting in a magnetic recording storage device is carried out with a preliminary measuring of write-read channel responses to all nonzero binary combinations of a given length. Decoding of the user data is performed according to a Viterbi algorithm, where the previously measured responses are used as expected samples for branch metric calculations. The measurement of the write-read channel responses and the decoding of the user data are fulfilled by a self-adjusting PRML receiver that contains a controllable clock recovery, a responses accumulator and an adjustable Viterbi detector. The controllable clock recovery produces a set of read-back signal samples containing exactly one sample per bit with or without phase error correction. The responses accumulator calculates averaged responses of the write-read channel. The adjustable Viterbi detector reconstructs the user data that were written to the disk.