Abstract: Example channel circuits, data storage devices, and methods for using zero force adaptation to equalize a read data signal based on known data are described. A known user data signal may be determined during prior read operations and used with a residue term from the equalized read data signal to adapt the tap weights for an equalizer filter using a zero force adaptation algorithm. For example, the known user data signal may be determined by a soft output detector (e.g., SOVA detector) or full or partial decoding by an iterative decoder (e.g., LDPC decoder) and fed back for adapting the equalizer.

Abstract: Example channel circuits, data storage devices, and methods for using zero force adaptation to equalize a read data signal based on known data are described. A known user data signal may be determined during prior read operations and used with a residue term from the equalized read data signal to adapt the tap weights for an equalizer filter using a zero force adaptation algorithm. For example, the known user data signal may be determined by a soft output detector (e.g., SOVA detector) or full or partial decoding by an iterative decoder (e.g., LDPC decoder) and fed back for adapting the equalizer.

Abstract: Example systems, read channels, and methods provide bit value detection from an encoded data signal using a neural network soft information detector. The neural network detector determines a set of probabilities for possible states of a data symbol from the encoded data signal. A soft output detector uses the set of probabilities for possible states of the data symbol to determine a set of bit probabilities that are iteratively exchanged as extrinsic information with an iterative decoder for making decoding decisions. The iterative decoder outputs decoded bit values for a data unit that includes the data symbol.

Abstract: Example systems, read channels, and methods provide bit value detection from an encoded data signal using a neural network soft information detector. The neural network detector determines a set of probabilities for possible states of a data symbol from the encoded data signal. A soft output detector uses the set of probabilities for possible states of the data symbol to determine a set of bit probabilities that are iteratively exchanged as extrinsic information with an iterative decoder for making decoding decisions. The iterative decoder outputs decoded bit values for a data unit that includes the data symbol.

Abstract: A method and apparatus for generating a laser signal for driving a laser used in thermal-assisted recording. A channel of a hard drive generates a high-frequency component of the laser signal—e.g., a periodic wave or series of pulses—and synchronizes the phase of the laser signal with a corresponding write data signal which controls the magnetization of data bits within the magnetic disk of the hard drive. The channel may be connected to a read/write integrated circuit via a channel interconnect. The read/write circuit may include a second phase control to compensate for any phase shift and an adder circuit to combine the transmitted high-frequency laser with a DC bias. Further, the read/write circuit may include a feedback loop for adjusting the DC bias based on environmental parameters of the hard drive such as temperature.

Abstract: A method and apparatus for generating a laser signal for driving a laser used in thermal-assisted recording. A channel of a hard drive generates a high-frequency component of the laser signal—e.g., a periodic wave or series of pulses—and synchronizes the phase of the laser signal with a corresponding write data signal which controls the magnetization of data bits within the magnetic disk of the hard drive. The channel may be connected to a read/write integrated circuit via a channel interconnect. The read/write circuit may include a second phase control to compensate for any phase shift and an adder circuit to combine the transmitted high-frequency laser with a DC bias. Further, the read/write circuit may include a feedback loop for adjusting the DC bias based on environmental parameters of the hard drive such as temperature.

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: 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 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: 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.