Whitening of data-dependent, non-stationary noise in an inter-symbol interference channel detector

• US 20060093075A1
• Filed: 10/28/2004
• Published: 05/04/2006
• Est. Priority Date: 10/28/2004
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Radich, William M.
• Granted Patent: US 7,471,746 B2
• Time in Patent Office: Days
• US Class Current: 375/341
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals
• CPC Class Codes: G11B 20/10296 using the Viterbi algorithm

Abstract

A decoder includes cascaded lattice filters that receive encoded data and include adaptive inputs and output taps. A tap control couples a selected output tap to a viterbi input as a function of a viterbi output. A noise adaptation circuit provides adjustment to the adaptive inputs as a function of the viterbi output to whiten non-stationary noise that is received with the encoded data.

Claims

1. A decoder, comprising:

cascaded lattice filters that receive encoded data and that include adaptive inputs and output taps;

a viterbi path memory unit and survival register unit circuit with a viterbi input and a viterbi output;

a tap control coupling a selected output tap to the viterbi input as a function of the viterbi output; and

a noise adaptation circuit that provides an adjustment to the adaptive inputs as a function of the viterbi output to whiten non-stationary noise.

2. The decoder of claim 1 wherein the cascaded lattice filters include processors, each processor including a reflection coefficient that is adjusted by the adjustment.

3. The decoder of claim 2 wherein the adjustment of the reflection coefficients is independent of the output tap selected by the tap control.

4. The decoder of claim 2 wherein the adjustment comprises a plurality of adjustments for each cascaded lattice filter, each of the plurality of adjustments being independent of one another.

5. The decoder of claim 1 wherein the noise adaptation circuit provides the adjustment as a function of past noise at the viterbi output.

6. The decoder of claim 1 wherein the noise adaptation circuit comprises a noise detector that generates a noise sample output indicating past noise samples in the viterbi output.

7. The decoder of claim 1 wherein the encoded data is received from a communication medium that injects non-stationary noise into the encoded data and the selected tap output provides data in which the non-stationary noise is whitened.

8. The decoder of claim 1 wherein the viterbi input has a fixed range, and the viterbi path memory unit and survival register unit circuit has a fixed scale to process the fixed range.

9. The decoder of claim 1 wherein the viterbi input has a fixed scale and the viterbi path memory unit and survival register unit circuit has a fixed resolution to process the fixed scale.

10. The decoder of claim 1 wherein the tap control selects an output tap based on current decoded data at the viterbi output.

11. A method of decoding, comprising:

providing encoded data to cascaded lattice filters that include adaptive inputs and output taps;

selecting an output tap as a function of a viterbi output of a viterbi path memory unit and survival register unit circuit and providing the selected output tap to viterbi input of the circuit; and

providing an adjustment to the adaptive inputs as a function of the viterbi output to whiten non-stationary noise.

12. The method of claim 11 wherein the cascaded lattice filters include processors with reflection coefficients, and:

adjusting the reflection coefficients with the adaptive inputs.

13. The method of claim 12 further comprising:

adjusting the reflection coefficients independently from the output tap that is selected.

14. The method of claim 12, further comprising:

adjusting a reflection coefficient of each cascaded lattice filter independently from adjustment of the reflection coefficient of other cascaded lattice filters.

15. The method of claim 11, further comprising:

providing the adjustment as a function of past noise at the viterbi output.

16. The method of claim 11, further comprising:

providing a noise detector indicating past noise samples in the viterbi output.

17. The method of claim 11, further comprising:

receiving the encoded data from a communication medium that injects non-stationary noise into the encoded data; and

providing decoded data at the viterbi input with the non-stationary noise whitened.

18. The method of claim 11, further comprising:

providing the viterbi input with a fixed range, and

providing the viterbi path memory unit and survival register unit circuit with a fixed scale to process the fixed range.

19. The method of claim 11, further comprising:

providing the viterbi input with a fixed scale; and

providing the viterbi path memory unit and survival register unit circuit with a fixed resolution to process the fixed scale.

20. The method of claim 11, further comprising:

selecting an output tap based on current data at the viterbi output.

21. A decoder, comprising:

cascaded lattice filters that receive encoded data and that include adaptive inputs and output taps;

a viterbi path memory unit and survival register unit circuit with a viterbi input and a viterbi output;

means for coupling a selected output tap to the viterbi input as a function of the viterbi output; and

means for provides an adjustment to the adaptive inputs as a function of the viterbi output to whiten non-stationary noise.