Abstract: A receiving device may be configured to derive an oversampled dibit pulse response estimate using symbols sampled at substantially the read channel symbol rate of the receiving device. The receiving device may include a data acquisition circuit configured to digitize data derived from a memory medium, a symbol timing loop and read circuit, as well as a dibit pulse estimation circuit configured to estimate the oversampled dibit pulse response using symbols sampled at the read channel rate of the receiving device without disturbing the symbol timing loop and read circuit.

Abstract: A receiving device may be configured to derive an oversampled dibit pulse response estimate using symbols sampled at substantially the read channel symbol rate of the receiving device. The receiving device may include a data acquisition circuit configured to digitize data derived from a memory medium, as well as a dibit pulse estimation circuit configured to estimate the oversampled dibit pulse response using symbols sampled at the read channel rate of the receiving device.

Abstract: Various embodiments of the present invention provide apparatuses and methods for filtering a digital signal with a Nyquist constrained digital finite impulse response filter. For example, an apparatus for filtering digital data is disclosed that includes a digital finite impulse response filter having a plurality of taps. The apparatus also includes a tap weight controller connected to the digital finite impulse response filter, operable to adjust a tap weight for each of a subset of the taps such that a magnitude of a Nyquist response of the digital finite impulse response filter remains within a constraint range.

Abstract: In one embodiment, a (hard-drive) read channel has a (DFIR equalization) filter, whose tap coefficients are adaptively updated. A reset controller monitors an (LLR) signal generated downstream of the filter to automatically determine when to reset the filter, e.g., by reloading an initial set of user-specified tap coefficients. For LLR values, the reset controller determines to reset the filter when the reset controller detects that too many recent LLR values have confidence values that are too low. When implemented in a hard-drive read channel, the reset controller can reset the filter one or more times during read operations within a sector of the hard drive.

Abstract: Devices, systems, and techniques for equalization and detection include, in at least some implementations, first circuitry configured to produce first equalized data responsive to input data by reducing a first characteristic of the input data wherein the first characteristic is noise, inter symbol interference (ISI) or both, a first detector that produces first output data responsive to the first equalized data, second circuitry configured to reduce a second characteristic different from the first characteristic to produce second equalized data, the second equalized data being generated based on the first equalized data, and a second detector that produces second output data responsive to the second equalized data.

Abstract: Methods and structure described herein provide for adjusting an error correction capability of an LDPC error correction code. For example, the system of one embodiment includes a decoder adapted to decode data that has been encoded with a LDPC error correction code. The system also includes a detector communicatively coupled to the decoder and adapted to estimate bit values in the data prior to decoding by the decoder. The detector is further adapted to change bit values based on bit value estimations to reduce the error correction capability of the LDPC error correction code. The reduction in error correction capability is adjustable such that sector failure rates of storage devices may be incrementally analyzed.

Abstract: A channel decoder including an amplifier configured to amplify a signal; a first summer configured to generate an output signal based on the signal amplified by the amplifier; and a Viterbi detector module configured to, based on the output signal, generate a first estimate signal and a second estimate signal, wherein the first estimate signal and the second estimate signal respectively indicate an estimate of data in the signal. The channel decoder further includes a second summer configured to generate a first error signal indicating a first gradient based on the first estimate signal; and a third summer configured to generate a second error signal indicating a second error gradient based on the second estimate signal. The first summer is configured to generate the output signal based on (i) the first error signal and (ii) the second error signal.

Abstract: Various embodiments of the present invention provide systems and methods for data processing system. As one example, a data processing circuit is described that includes an analog to digital converter, an online timing loop, and an offline timing loop. The analog to digital converter receives an analog input and provides a first series of data samples Each bit of the first series of data samples corresponds to the analog input at a time controlled by an updated sampling clock. The online timing loop modifies the updated sampling clock based at least in part upon a processed version of the first series of data samples.

Abstract: Methods and apparatus are provided for processing a signal in a read channel using a selective oversampled analog to digital conversion. The disclosed selective oversampled analog to digital conversion simplifies the analog design by transferring at least a portion of the equalization and/or filtering processes to the digital domain. An oversampled analog to digital conversion is applied to an analog input signal to generate a plurality of digital samples for a given bit interval. The plurality of digital samples for a given bit interval are applied to a corresponding plurality of data detectors to obtain a detected output. The plurality of digital samples for a given bit interval may have a phase offset relative to one another. The detected output may be obtained, for example, by summing the outputs of the plurality of data detectors or by aggregating weighted outputs of the plurality of data detectors.

Abstract: A system for identifying and compensating for non-linear transition shift in a magnetic medium data storage device is disclosed. The non-linear transition shift compensation system includes a non-linear transition shift estimation module adapted to generate non-linear transition shift estimates for specific bit patterns. The system further includes a pre-compensation module adapted to adjust the temporal spacing of binary transitions written to the magnetic medium based on the non-linear transition shift estimates generated by the non-linear transition shift estimation module for specific bit patterns corresponding to bit patterns appearing in the data being written to the magnetic medium.

Abstract: Various embodiments of the present invention provide systems and methods for out of order memory management. For example, a method for out of order data processing is disclosed. The method includes providing an out of order codeword memory circuit that includes a number of codeword memory locations in a codeword memory area and the same number of index values in an index area. Each of the index values corresponds to a respective one of the codeword memory locations. The methods further include receiving a data set; storing the data set to one of the codeword memory locations; receiving an indication that the data set stored in the one of the codeword memory locations has completed processing; and grouping an index value corresponding to the one of the codeword memory locations with one or more other index values corresponding to unused codeword memory locations.

Abstract: Various embodiments of the present invention provide systems, apparatuses and methods for performing analog to digital conversion. For example, an analog to digital converter circuit is discussed that includes an analog input, a number of analog to digital converters and a generalized beamformer. The analog to digital converters are operable to receive the analog input and to yield a number of digital streams. Each of the analog to digital converters samples the analog input with different phase offsets. The generalized beamformer is operable to weight and combine the digital streams to yield a digital output.

Abstract: Various embodiments of the present invention provide systems and methods for phase offset based spectral aliasing compensation. For example, a circuit for spectral aliasing reduction is disclosed that includes a phase shift circuit operable to phase shift an analog input signal and to provide a phase shifted analog signal; a first analog to digital converter circuit operable to provide a first series of digital samples corresponding to the analog input signal at a sampling frequency; a second analog to digital converter circuit operable to provide a second series of digital samples corresponding to the phase shifted analog signal at the sampling frequency; and an averaging circuit operable to average the first series of digital samples with the second series of digital samples to yield an average output.

Abstract: The present invention is a device for detecting short burst errors. The device includes a first signal input, wherein the first signal input is configured to receive a first signal. The device includes a second signal input, wherein the second signal input is configured to receive a second signal. The device includes a logic gate, wherein the logic gate is operable for receiving the first signal via the first signal input, receiving the second signal via the second signal input, and generating a logic output gate signal based on the received first signal and the second signal. Furthermore, the device includes a filter, wherein the filter is configured for receiving the logic output gate signal from the logic gate and generates a filter output signal based upon the received logic output gate signal, wherein the filter output signal is operable for flagging errors.

Abstract: Various embodiments of the present invention provide systems and methods for data processing system. As one example, a data processing circuit is described that includes an analog to digital converter, an online timing loop, and an offline timing loop. The analog to digital converter receives an analog input and provides a first series of data samples Each bit of the first series of data samples corresponds to the analog input at a time controlled by an updated sampling clock. The online timing loop modifies the updated sampling clock based at least in part upon a processed version of the first series of data samples.

Abstract: Various embodiments of the present invention provide systems and methods for servo data based harmonics calculation. For example, a circuit for determining harmonics is disclosed that includes an analog to digital conversion circuit that provides a series of digital samples corresponding to a pattern within a servo data region of a storage medium, and a harmonic calculation circuit. The harmonic calculation circuit is operable to calculate a first harmonic value for the series of digital samples, calculate a second harmonic value for the series of digital samples, and calculate a ratio of the first harmonic value to the second harmonic value.

Abstract: A system and method are provided to detect defects in a data storage medium by sampling data read from the data storage medium. Time referenced samples of data read from the data storage medium are equalized to mediate the effects of channel noise and the equalized samples are decoded by a decoder, such as a Viterbi decoder. The decoded signal is then reconstructed through a reconstruction filter to approximate the equalized signal. The equalized data signal and the reconstructed data signal are then combined and compared in a bit-by-bit deconstruction scheme to determine, based on a variation between the signal elements, that a defect exists on the data storage medium. Additional action is then taken to mediate the effects of attempting to process corrupted data based on the defect by isolating the defective bit.

Abstract: In one embodiment, a signal processing receiver has a branch-metric calibration (BMC) unit that receives (i) sets of four hard-decision bits from a channel detector and (ii) a noise estimate. The BMC unit has two or more update blocks (e.g., tap-weight update and/or bias-compensation blocks) that generate updated parameters used by a branch-metric unit of the channel detector to improve channel detection. The two or more update blocks generate the updated parameters based on (i) the sets of four hard-decision bits, (ii) the noise estimate, and (iii) bandwidth values. The bandwidth values for at least two of the two or more update blocks are selected such that they are different from one another. Selecting different bandwidth values may reduce the bit-error rate for the receiver over the bit-error rate that may be achieved by selecting the bandwidth values to be the same as one another.

Abstract: Various embodiments of the present invention provide systems and methods for data processing. As an example, a data processing circuit is disclosed that includes a codeword detector circuit operable to apply a codeword based data detection algorithm to a data input corresponding to an encoded servo data region to yield a detected output, and a servo address mark processing circuit operable to identify a pre-defined pattern in the detected output.

Abstract: Various embodiments of the present invention provide systems and methods for servo data based harmonics calculation. For example, a method for calculating harmonics is disclosed that includes: providing a data processing circuit; receiving a first data set derived from a data source during a servo data processing period; performing a first harmonics calculation using the first data set to yield a first harmonics ratio; receiving a second data set derived from a source other than the previously mentioned data source during a user data processing period; performing a second harmonics calculation using the second data set to yield a second harmonics ratio; and calculating a ratio of the first harmonics ratio to the second harmonics ratio.