Abstract: An apparatus for correcting crosstalk in an array reader magnetic recording system includes an array reader comprising a number of read heads operable to read data from a magnetic storage medium, a preamplifier configured to amplify the signals from the read heads, and a crosstalk correction circuit configured to reduce crosstalk between signals from the read heads.

Abstract: An apparatus for measuring cross-talk in an array reader magnetic storage system includes an array reader with multiple read heads operable to read data from a magnetic storage medium, a first preamplifier connected to a first read head, a second preamplifier connected to a second read head, and a cross-talk measurement circuit connected to the first preamplifier and to the second preamplifier, operable to measure cross-talk between a first signal from the first read head and a second signal from the second read head.

Abstract: An apparatus for measuring cross-talk in an array reader magnetic storage system includes an array reader with multiple read heads operable to read data from a magnetic storage medium, a first preamplifier connected to a first read head, a second preamplifier connected to a second read head, and a cross-talk measurement circuit connected to the first preamplifier and to the second preamplifier, operable to measure cross-talk between a first signal from the first read head and a second signal from the second read head.

Abstract: Two levels of error correction decoding are performed using first and second level decoders. A composite code formed by combining an inner component code and an outer component code can be used to decode the data and correct any errors. Performing two level decoding using a composite code allows the size of the inner parity block to be reduced to a single Reed-Solomon symbol while keeping a good code rate. The first level decoder generates soft information. The soft information can indicate a most likely error event for each possible syndrome value of the inner component code. The soft information can also include error metric values for each of the most likely error events. The second level decoder generates corrected syndrome values based on the soft information using the outer component code. The most likely trellis path that corresponds to the corrected syndrome values is then selected.

Abstract: Two levels of error correction decoding are performed using first and second level decoders. A composite code formed by combining an inner component code and an outer component code can be used to decode the data and correct any errors. Performing two level decoding using a composite code allows the size of the inner parity block to be reduced to a single Reed-Solomon symbol while keeping a good code rate. The first level decoder generates soft information. The soft information can indicate a most likely error event for each possible syndrome value of the inner component code. The soft information can also include error metric values for each of the most likely error events. The second level decoder generates corrected syndrome values based on the soft information using the outer component code. The most likely trellis path that corresponds to the corrected syndrome values is then selected.

Abstract: Two levels of error correction decoding are performed using first and second level decoders. A composite code formed by combining an inner component code and an outer component code can be used to decode the data and correct any errors. Performing two level decoding using a composite code allows the size of the inner parity block to be reduced to a single Reed-Solomon symbol while keeping a good code rate. The first level decoder generates soft information. The soft information can indicate a most likely error event for each possible syndrome value of the inner component code. The soft information can also include error metric values for each of the most likely error events. The second level decoder generates corrected syndrome values based on the soft information using the outer component code. The most likely trellis path that corresponds to the corrected syndrome values is then selected.

Abstract: An error correction encoder inserts redundant parity information into a data stream to improve system reliability. The encoder can generate the redundant parity information using a composite code. Dummy bits are inserted into the data stream in locations reserved for parity information generated by subsequent encoding. The error correction code can have a uniform or a non-uniform span. The span corresponds to consecutive channel bits that are within a single block of a smaller parity code that is used to form a composite code. The span lengths can be variant across the whole codeword by inserting dummy bits in less than all of the spans.

Abstract: Embodiments of the invention provide techniques for optimizing the detector target polynomials in read/write channels to achieve the best error rate performance in recording devices. In one embodiment, a method of obtaining a detector target polynomial of a read/write channel to achieve best error rate performance in a recording device comprises: providing an initial detector target for the read/write channel; measuring a noise autocorrelation of the read/write channel at the output of equalizer using channel hardware; computing a noise autocorrelation at the output of the 1st stage target based on the measured noise autocorrelation of the read/write channel at the output of equalizer; calculating optimal coefficients for the noise whitening filter; and obtaining the optimal detector target polynomial of the read/write channel using the calculated coefficients for noise whitening filter.

Abstract: A data storage system includes an encoder subsystem comprising an error correction code encoder, a modulation encoder, and a precoder, and a decoder subsystem similarly comprising a detector, an inverse precoder, a channel decoder, and an error correction code decoder. The error correction encoder applies an error correction code to the incoming user bit stream, and the modulation encoder applies so-called modulation or constrained coding to the error correction coded bit stream. The precoder applies so-called preceding to the modulation encoded bit stream. However, this preceding is applied to selected portions of the bit stream only. There can also be a permutation step where the bit sequence is permuted after the modulation encoder before preceding is applied by the precoder. The decoder subsystem operates in the inverse manner.

Abstract: Two levels of error correction decoding are performed using first and second level decoders. A composite code formed by combining an inner component code and an outer component code can be used to decode the data and correct any errors. Performing two level decoding using a composite code allows the size of the inner parity block to be reduced to a single Reed-Solomon symbol while keeping a good code rate. The first level decoder generates soft information. The soft information can indicate a most likely error event for each possible syndrome value of the inner component code. The soft information can also include error metric values for each of the most likely error events. The second level decoder generates corrected syndrome values based on the soft information using the outer component code. The most likely trellis path that corresponds to the corrected syndrome values is then selected.

Abstract: An error correction encoder inserts redundant parity information into a data stream to improve system reliability. The encoder can generate the redundant parity information using a composite code. Dummy bits are inserted into the data stream in locations reserved for parity information generated by subsequent encoding. The error correction code can have a uniform or a non-uniform span. The span corresponds to consecutive channel bits that are within a single block of a smaller parity code that is used to form a composite code. The span lengths can be variant across the whole codeword by inserting dummy bits in less than all of the spans.

Abstract: Embodiments of the invention provide techniques for optimizing the detector target polynomials in read/write channels to achieve the best error rate performance in recording devices. In one embodiment, a method of obtaining a detector target polynomial of a read/write channel to achieve best error rate performance in a recording device comprises: providing an initial detector target for the read/write channel; measuring a noise autocorrelation of the read/write channel at the output of equalizer using channel hardware; computing a noise autocorrelation at the output of the 1st stage target based on the measured noise autocorrelation of the read/write channel at the output of equalizer; calculating optimal coefficients for the noise whitening filter; and obtaining the optimal detector target polynomial of the read/write channel using the calculated coefficients for noise whitening filter.

Abstract: A method and apparatus for providing a read channel having imbedded channel signal analysis is disclosed.

Abstract: A method and apparatus for providing a read channel having combined parity and non-parity post processing is disclosed. A post-processor combines parity and non-parity post processing to make both parity and non-parity corrections so that error events that cannot be detected by parity may be corrected. Non-parity detectable error events are only kept for consideration if their likelihood is above a set threshold.

Abstract: Non-uniform modulation encoding techniques are provided to prevent data from containing bit patterns that are prone to errors during read back. Modulation encoding is performed on a data stream to remove error prone bit patterns. Unconstrained data, such as error check parity, that is inserted into the modulated data stream may contain error prone bit patterns. Stricter modulation constraints are enforced on bits that are next to the unconstrained data, than on the remaining bits. By enforcing stricter modulation constraints on these bits, an entire data bit stream can have a desired modulation constraint.

Abstract: Techniques are provided for applying modulation constraints to data streams using a short block encoder. A short block encoder encodes a subset of the bits in a data stream. Then, the even and odd interleaves in a data stream are separated into two data paths. A first modulation encoder encodes the even interleave according to a first modulation constraint. A second modulation encoder encodes the odd interleave according to a second modulation constraint, which in general coincides with the modulation constraint for even interleave.

Abstract: A hard disk drive (HDD) holds data using a biphase scheme. A plurality of matched filters are used to detect binary data represented by the biphase pattern without the need for synchronous sampling or equalization.

Abstract: Techniques are provided for applying modulation constraints to data by using periodically changing symbol mappings to replace certain prohibited error prone data patterns. Initially, user data in a first base is mapped to integers of a second base using a base conversion technique. The integers in the second base correspond to symbols. Subsequently, periodically changing symbol mappings are performed during which prohibited symbols generated during base conversion are mapped to permitted symbols. The periodically changing symbol mappings occur in multiple phases, and the prohibited symbols are different in each phase. The resulting data is processed by a precoder in some embodiments.

Abstract: An apparatus for providing dynamic equalizer optimization is disclosed. The present invention solves the above-described problems by providing equalizer coefficient updates that converge towards the same solution as the direct method without having to first write a known pattern to the disk or requiring any prior knowledge of the data already written on the disk. The adaptive cosine function may be used to modify only a DFIR tap set, only the j and k parameters of a cosine equalizer or to modify both the tap set for a DFIR filter and the j and k parameters of the cosine equalizer. Another algorithm, such as the LMS algorithm, may be used to modify parameters not modified by the cosine algorithm.

Abstract: A data storage system includes an encoder subsystem comprising an error correction code encoder, a modulation encoder, and a precoder, and a decoder subsystem similarly comprising a detector, an inverse precoder, a channel decoder, and an error correction code decoder. The error correction encoder applies an error correction code to the incoming user bit stream, and the modulation encoder applies so-called modulation or constrained coding to the error correction coded bit stream. The precoder applies so-called precoding to the modulation encoded bit stream. However, this precoding is applied to selected portions of the bit stream only. There can also be a permutation step where the bit sequence is permuted after the modulation encoder before precoding is applied by the precoder. The decoder subsystem operates in the inverse manner.