Using a measured error to determine coefficients to provide to an equalizer to use to equalize an input signal

• US 20070133115A1
• Filed: 12/08/2005
• Published: 06/14/2007
• Est. Priority Date: 12/08/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Jelitto, Jens, Oelcer, Sedat, Eleftheriou, Evangelos, Hutchins, Robert
• Granted Patent: US 7,436,615 B2
• Time in Patent Office: Days
• US Class Current: 360/65
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals
• CPC Class Codes: G11B 20/10046 filtering or equalising, e.g. setting the tap weights of an FIR filter
• CPC Class Codes: G11B 5/00817 on longitudinal tracks only, e.g. for serpentine format recording
• CPC Class Codes: G11B 5/09 Digital recording

Abstract

Provided are a read channel, storage drive and method using a measured error to determine coefficients to provide to an equalizer to use to equalize an input signal. A read channel is incorporated in a storage device to process signals read from a storage medium. An equalizer uses coefficients to equalize input read signals to produce equalizer output signals. A detector processes adjusted equalizer output signals to determine output values comprising data represented by the input read signals. An equalizer adaptor is enabled to provide a reference measured error and coefficients used to produce the adjusted equalizer signals that are associated with the reference measured error. The equalizer adaptor computes new equalizer coefficients to use to equalize input read signals that result in a new measured error from the detector and computes a new measured error for the new equalizer coefficients. The equalizer adaptor determines whether the new measured error is degraded with respect to the reference measured error and saves the new equalizer coefficients and the new measured error in response to determining that the new measured error is not degraded with respect to the reference measured error. The equalizer adaptor provides the equalizer coefficients associated with the reference measured error to the equalizer to use to equalize input read signals in response to determining that the new measured error is degraded with respect to the reference measured error.

Claims

1. A read channel incorporated in a storage device to process signals read from a storage medium, comprising:

an equalizer using coefficients to equalize input read signals to produce equalizer output signals;

a detector processing adjusted equalizer output signals to determine output values comprising data represented by the input read signals; and

an equalizer adaptor enabled to perform operations comprising;

providing a reference measured error and coefficients used to produce the adjusted equalizer signals that are associated with the reference measured error;

computing new equalizer coefficients to use to equalize input read signals that result in a new measured error from the detector;

computing a new measured error for-the new equalizer coefficients;

determining whether the new measured error is degraded with respect to the reference measured error;

saving the new equalizer coefficients and the new measured error in response to determining that the new measured error is not degraded with respect to the reference measured error; and

.

providing the equalizer coefficients associated with the reference measured error to the equalizer to use to equalize input read signals in response to determining that the new measured error is degraded with respect to the reference measured error.

2. The read channel of claim 1, wherein the measured errors are based on adjusted equalizer output signals and output values from the detector.

3. The read channel of claim 1, wherein the equalizer adaptation is stopped and fixed equalizer coefficients are provided to the equalizer to use to equalize the input read signals until an end of a data set is detected in response to determining that the new measured error is degraded with respect to the reference measured error

4. The read channel of claim 1, wherein the new equalizer coefficients are saved and the new measured error is saved as the reference measured error in response to detecting an end of a data set and to detecting an improvement of the new measured error over the reference measured error.

5. The read channel of claim 1, wherein the measured errors comprise the mean squared values of the errors measured as a difference of an input to the detector and an output from the detector, and wherein the measured errors correspond to a signal-to-noise ratio at the input to the detector.

6. The read channel of claim 1, wherein the equalizer adaptor is further enabled to perform:

providing fixed coefficients to the equalizer to use to equalize the read input signals for an initial measured error computation phase; and

computing the measured error from the equalized input signal.

7. The read channel of claim 1, wherein the new measured error is calculated based on the input signals equalized using fixed coefficients, wherein the equalizer adaptor is further enabled to perform:

saving the new measured error as the reference measured error and saving the fixed coefficients to use to equalize the input signal in response to determining that there exists no value for the reference measured error;

determining whether the new measured error is degraded with respect to the reference measured error in response to using the fixed coefficients for an initial measured error computation phase; and

saving the new measured error as the reference measure error and saving the fixed coefficients to use to equalize the input signal in response to determining that the new measured error is degraded beyond some margin.

8. The read channel of claim 1, wherein the operations of calculating the new coefficients, using the new coefficients to equalize input read signals to produce equalizer output signals, and determining whether the new measured error is degraded are performed until detecting an end of a data set, wherein the equalizer adaptor is further enabled to perform:

determining whether to stop equalizer adaptation and to provide fixed coefficients to the equalizer to use to equalize the input signal in response to determining that the new measured error is degraded with respect to the reference measured error beyond some margin.

9. The read channel of claim 8, wherein the equalizer adaptor is further enabled to perform:

determining whether the new measured error is degraded;

saving the new coefficients and the new measured error as reference measured error when the measured error is not degraded with respect to the reference measured error; and

reloading the previous coefficients and the previous measured error as reference measured error when the measured error is degraded with respect to the reference measured error.

10. The read channel of claim 9, wherein a user settable parameter indicates whether to use the fixed coefficients for an initial measured error computation phase to process input signals from the next data set.

11. The read channel of claim 1, wherein the measured error is based on a difference of an input and output of the detector, and wherein the new coefficients are calculated using the output of the detector.

12. A storage drive for performing Input/Output (I/O) operations with respect to a storage medium coupled to the storage drive, comprising:

a head to read data from the storage medium; and

a read channel in data communication with the head to process signals the head reads from the storage medium, comprising;

an equalizer using coefficients to equalize input read signals to produce equalizer output signals;

a detector processing adjusted equalizer output signals to determine output values comprising data represented by the input read signals; and

an equalizer adaptor enabled to perform operations comprising;

providing a reference measured error and coefficients used to produce the adjusted equalizer signals that are associated with the reference measured error;

computing new equalizer coefficients to use to equalize input read signals that result in a new measured error from the detector;

computing a new measured error for the new equalizer coefficients;

determining whether the new measured error is degraded with respect to the reference measured error;

saving the new equalizer coefficients and the new measured error in response to determining that the new measured error is not degraded with respect to the reference measured error; and

.

providing the equalizer coefficients associated with the reference measured error to the equalizer to use to equalize input read signals in response to determining that the new measured error is degraded with respect to the reference measured error.

13. The storage drive of claim 12, wherein the equalizer adaptation is stopped and fixed equalizer coefficients are provided to the equalizer to use to equalize the input read signals until an end of a data set is detected in response to determining that the new measured error is degraded with respect to the reference measured error

14. The storage drive of claim 12, wherein the new equalizer coefficients are saved and the new measured error is saved as the reference measured error in response to detecting an end of a data set and to detecting an improvement of the new measured error over the reference measured error.

15. The storage drive of claim 12, wherein the new measured error is calculated based on the input signals equalized using fixed coefficients, wherein the equalizer adaptor is further enabled to perform:

saving the new measured error as the reference measured error and saving the fixed coefficients to use to equalize the input signal in response to determining that there exists no value for the reference measured error;

determining whether the new measured error is degraded with respect to the reference measured error in response to using the fixed coefficients for an initial measured error computation phase; and

saving the new measured error as the reference measure error and saving the fixed coefficients to use to equalize the input signal in response to determining that the new measured error is degraded beyond some margin.

16. The storage drive of claim 12, wherein the operations of calculating the new coefficients, using the new coefficients to equalize input read signals to produce equalizer output signals, and determining whether the new measured error is degraded are performed until detecting an end of a data set, wherein the equalizer adaptor is further enabled to perform:

determining whether to stop equalizer adaptation and to provide fixed coefficients to the equalizer to use to equalize the input signal in response to determining that the new measured error is degraded with respect to the reference measured error beyond some margin.

17. A method for processing signals read from a storage medium, comprising:

using coefficients to equalize input read signals to produce equalizer output signals;

processing adjusted equalizer output signals to determine output values comprising data represented by the input read signals;

providing a reference measured error and coefficients used to produce the adjusted equalizer signals that are associated with the reference measured error;

computing new equalizer coefficients to use to equalize input read signals that result in a new measured error from the detector;

computing a new measured error for the new equalizer coefficients;

determining whether the new measured error is degraded with respect to the reference measured error;

saving the new equalizer coefficients and the new measured error in response to determining that the new measured error is not degraded with respect to the reference measured error; and

.

providing coefficients associated with the reference measured error to an equalizer to use to equalize input read signals in response to determining that the new measured error is degraded with respect to the reference measured error.

18. The method of claim 17, wherein equalizer adaptation is stopped and fixed equalizer coefficients are provided to the equalizer to use to equalize the input read signals until an end of a data set is detected in response to determining that the new measured error is degraded with respect to the reference measured error

19. The method of claim 17, wherein the new equalizer coefficients are saved and the new measured error is saved as the reference measured error in response to detecting an end of a data set and to detecting an improvement of the new measured error over the reference measured error.

20. The method of claim 17, wherein the new measured error is calculated based on the input signals equalized using fixed coefficients, further comprising:

saving the new measured error as the reference measured error and saving the fixed coefficients to use to equalize the input signal in response to determining that there exists no value for the reference measured error;

determining whether the new measured error is degraded with respect to the reference measured error in response to using the fixed coefficients for an initial measured error computation phase; and

saving the new measured error as the reference measure error and saving the fixed coefficients to use to equalize the input signal in response to determining that the new measured error is degraded beyond some margin.

21. The method of claim 17, wherein the operations of calculating the new coefficients, using the new coefficients to equalize input read signals to produce equalizer output signals, and determining whether the new measured error is degraded are performed until detecting an end of a data set, further comprising:

determining whether to stop equalizer adaptation and to provide fixed coefficients to the equalizer to use to equalize the input signal in response to determining that the new measured error is degraded with respect to the reference measured error beyond some margin.