Apparatus, method, and system for correction of baseline wander

• US 7,589,649 B1
• Filed: 05/04/2007
• Issued: 09/15/2009
• Est. Priority Date: 05/08/2006
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Cheng, Chi Fung, Song, Hongxin, Aga, Arshan
• Primary Examiner(s): Nguyen; Linh V
• Application Number:
  US11/800,554
• Time in Patent Office: 865 Days
• Field of Search: 341/118, 341/120, 341/139, 341/143, 341/155
• US Class Current: 341/118
• CPC Class Codes: G11B 7/005 Reproducing G11B7/0065 takes precedence
• CPC Class Codes: H03M 1/1295 Clamping, i.e. adjusting the DC level of the input signal to a predetermined value

Abstract

Apparatuses, methods, and systems for compensating baseline offset in a read channel of an analog storage device. The apparatus generally includes an AC-coupling circuit configured to transfer an analog signal from an analog storage device to the read channel, a configurable current device coupled to the AC-coupling circuit, comparator coupled to the AC-coupling circuit, and logic coupled to the configurable current device and the comparator, wherein the logic is adapted to configure said current device in response to an output of at least one of the AC-coupling circuit and the comparator. The method generally includes the steps of coupling an analog storage device and the read channel with an AC-coupling circuit, detecting a baseline or a component of an analog signal at a node downstream from the AC-coupling circuit, and configuring a current device to modify the analog signal in response to detecting the baseline or a component of the analog signal, wherein the current device is coupled to a node downstream from the AC-coupling circuit and upstream from a signal processor configured to operate on the analog signal.

Claims

1. An apparatus for compensating baseline offset in a read channel, the apparatus comprising:

an AC-coupling circuit configured to transfer an analog signal from an analog storage device to said read channel;

a configurable current device comprising a resistor and at least one active current source and at least one active current sink, wherein said configurable current device is coupled to said AC-coupling circuit;

a comparator coupled to said AC-coupling circuit, wherein said comparator is configured to compare a voltage of said analog signal to a pre-determined voltage; and

logic coupled to said configurable current device and said comparator, wherein said logic is adapted to determine said baseline offset and to configure said configurable current device in response to an output of said comparator by providing a signal to said at least one active current source and said at least one active current sink to apply a current to said resistor to compensate for said baseline offset.

2. The apparatus of claim 1, wherein said AC-coupling circuit comprises an input coupled to a first terminal of a capacitor;

an output coupled to a second terminal of said capacitor and a first terminal of a resistor; and

a common node coupled to a second terminal of said resistor.

3. The apparatus of claim 1, wherein said AC-coupling circuit provides a differential output.

4. The apparatus of claim 1, wherein said signal to said at least one active current source and said at least one active current sink maintains a constant current through said resistor.

5. The apparatus of claim 1, wherein said signal to said at least one active current source and said at least one active current sink maintains a variable current through said resistor.

6. The apparatus of claim 5, wherein said logic provides a signal adapted to maintain a pulsed current in said configurable current device, wherein the pulsed current has a magnitude, frequency, and/or pulse width corresponding to said baseline offset.

7. The apparatus of claim 6, wherein said pulsed current has a pulse width less than a time constant of said AC-coupling circuit.

8. The apparatus of claim 1, wherein said configurable current device comprises at least one active current source and at least one active current sink coupled to a node between said AC-coupling circuit and said comparator.

9. The apparatus of claim 1, further comprising an amplifier coupled to an output of said AC-coupling circuit.

10. The apparatus of claim 9, wherein said configurable current device is configured to limit a current in said amplifier.

11. The apparatus of claim 1, wherein said comparator comprises a configurable voltage comparator.

12. The apparatus of claim 1, wherein said comparator comprises a converter.

13. The apparatus of claim 12, wherein said converter comprises an analog-to-digital converter.

14. The apparatus of claim 1, further comprising a digital-to-analog converter coupled to said configurable current device and said logic.

15. The apparatus of claim 1, wherein said configurable current device comprises a buffer coupled to an output of said AC-coupling circuit.

17. The apparatus of claim 9, wherein said configurable current device is coupled to an output of said amplifier.

16. An apparatus for compensating baseline offset in a read channel, the apparatus comprising:

an AC-coupling circuit configured to transfer an analog signal from an analog storage device to said read channel;

a configurable current device coupled to said AC-coupling circuit, wherein said configurable current device comprises a buffer coupled to an output of said AC-coupling circuit;

a resistor coupled at a first terminal to an output of said buffer and at a second terminal to an input of said comparator; and

at least one active current source and at least one active current sink coupled to said first terminal and/or said second terminal of said resistor;

a comparator coupled to said AC-coupling circuit, wherein said comparator is configured to compare a voltage of said analog signal to a pre-determined voltage; and

logic coupled to said configurable current device and said comparator, wherein said logic comprises a look-up table adapted to output a current device setting signal to said configurable current device in response to an output of at least one of said AC-coupling circuit and said comparator corresponding to said baseline offset.

18. A method of compensating baseline offset in a read channel, the method comprising:

coupling an analog storage device and said read channel with an AC-coupling circuit;

detecting a baseline or a component of an analog signal at a node downstream from said AC-coupling circuit;

determining an offset of said baseline or said component of said analog signal; and

configuring a current device to modify said analog signal in response to said offset of said baseline or said component of said analog signal,

wherein said current device is coupled to a node downstream from said AC-coupling circuit and upstream from a signal processor configured to operate on said analog signal, said current device comprises a resistor at least one active current source and at least one active current sink, and

wherein configuring said current device comprises applying a variable current through said resistor by controlling said at least one active current source and at said at least one active current sink in response to said offset of said baseline or said component of said analog signal.

19. The method of claim 18, wherein said coupling comprises receiving a first signal from said analog storage device at a first terminal of a capacitor in said AC-coupling circuit;

and transmitting a second signal to said read channel at a second terminal of said capacitor in said AC-coupling circuit.

20. The method of claim 18, further comprising comparing said analog signal or a component of said analog signal to one or more reference voltages.

21. The method of claim 18, wherein detecting said baseline or said component of said analog signal comprises filtering said analog signal or said component of said analog signal.

22. The method of claim 18, wherein detecting said baseline or said component of said analog signal comprises converting said analog signal or said component of said analog signal into a digital signal.

23. The method of claim 22, further comprising comparing said digital signal or component of said analog signal to one or more reference values.

24. The method of claim 18, wherein configuring said current device to modify said analog signal comprises sinking and/or sourcing current at a node between said AC-coupling circuit and said signal processor.

25. The method of claim 18, wherein configuring said current device to modify said analog signal comprises limiting a current through an amplifier coupled to said AC-coupling circuit and said signal processor.

26. The method of claim 18, wherein configuring said current device to modify said analog signal comprises sinking and/or sourcing current through said resistor said resistor being coupled to said AC-coupling circuit and said signal processor.

27. A method of compensating baseline offset in a read channel, the method comprising:

coupling an analog storage device and said read channel with an AC-coupling circuit;

detecting a baseline or a component of an analog signal at a node downstream from said AC-coupling circuit;

determining an offset of said baseline or said component of said analog signal; and

outputting a current device setting signal from a look-up-table to at least one active current source and/or said at least one active current sink in a current device to modify said analog signal in response to said offset of said baseline or said component of said analog signal, wherein said current device is coupled to a node downstream from said AC-coupling circuit and upstream from a signal processor configured to operate on said analog signal, said current device comprises a resistor, at least one active current source and at least one active current sink, and said current device modifies said analog signal by sinking and/or sourcing current through said resistor coupled to said AC-coupling circuit and said signal processor.

28. A method of compensating baseline offset in a read channel, the method comprising:

reading data from an analog storage device to generate an analog signal for transmission in said read channel;

comparing said analog signal to a reference or converting said analog signal to a digital signal;

determining said baseline offset after comparing said analog signal or converting said analog signal to said digital signal; and

configuring a current to be sourced to and/or sunk from a resistor by at least one active current source and at least one active current sink to compensate for said baseline offset in response to said digital signal or an outcome of said comparing step.

29. The method of claim 28, wherein comparing said analog signal to a reference or converting said analog signal to a digital signal comprises comparing said analog signal to one or more reference voltages.

30. The method of claim 28, further comprising filtering said analog signal.

31. The method of claim 28, wherein comparing said analog signal to a reference or converting said analog signal to a digital signal comprises converting said analog signal to said digital signal.