System and Method for Independently Adjusting Multiple Compensations Applied to a Signal

• US 20080056344A1
• Filed: 05/24/2007
• Published: 03/06/2008
• Est. Priority Date: 05/30/2006
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Hidaka, Yasuo
• Granted Patent: US 7,817,712 B2
• Time in Patent Office: Days
• US Class Current: 375/232
• CPC Class Codes: H04L 25/03885 adaptive
• CPC Class Codes: H04L 25/063 Setting decision thresholds using feedback techniques only

Abstract

In one embodiment of the present invention, a method for adjusting a signal includes applying a plurality of compensation for distortion to a signal to generate an output signal. The method also includes, using a clock signal, sampling the output signal to generate a plurality of data values and boundary values, each value comprising either a high value or a low value based on the sampling of the output signal. The method also includes detecting a transition in value between two successive data values and determining a sampled boundary value between the two successive data values. The method further includes based at least on the high or low values of the boundary value and a plurality of data values before or after the boundary value, independently adjusting each compensation applied to the signal.

Claims

1. A method for adjusting a signal, comprising:

applying a plurality of compensation for distortion to a signal to generate an output signal;

using a clock signal, sampling the output signal to generate a plurality of data values and boundary values, each value comprising either a high value or a low value based on the sampling of the output signal;

detecting a transition in value between two successive data values and determining a sampled boundary value between the two successive data values; and

based at least on the high or low values of the boundary value and a plurality of data values before or after the boundary value, independently adjusting each compensation applied to the signal.

2. The method of claim 1, wherein the plurality of compensation for distortion are applied in parallel.

3. The method of claim 2, wherein the application of parallel compensation comprises:

communicating a first portion of the signal on a first path and a second portion of the signal on a second path;

applying a first compensation to the first path and a second compensation to the second path; and

combining at least the first path and the second path to compensate the signal for the distortion.

4. The method of claim 2, wherein the parallel compensation are applied using multi-tap finite-impulse-response-filter equalization.

5. The method of claim 1, wherein the plurality of compensation for distortion are applied in series.

6. The method of claim 5, wherein a first compensation is applied before the distortion occurs, and a second compensation is applied after the distortion occurs.

7. The method of claim 6, wherein the first compensation is applied using transmitter pre-emphasis equalization, and the second compensation is applied using receiver linear equalization.

8. The method of claim 3, wherein the first path comprises an unmodified signal path and the second path comprises a first-order derivative signal path.

9. The method of claim 3, wherein the first compensation and the second compensation are independently adjusted based only on the high or low values of the boundary value and the plurality of data values before the boundary value.

10. The method of claim 3, wherein the first compensation and the second compensation are independently adjusted based only on the high or low values of the boundary value and the two data values arriving immediately before the two successive data values.

11. The method of claim 3, further comprising:

communicating a third portion of the input data signal on a third path;

applying a third compensation to the third path;

combining at least the first path, the second path, and the third path to compensate the signal for the distortion; and

based at least on the high or low values of the boundary value and the plurality of data values before or after the boundary value, independently adjusting the third compensation applied to the third path.

12. The method of claim 11, wherein the compensation applied to the third path is decreased if:

the high or low value of the boundary value is different than the high or low value of the data value 1.5 symbols before the boundary value; and

the high or low value of the data value 1.5 symbols before the boundary value is different than the high or low value of the data value 2.5 symbols before the boundary value.

13. The method of claim 1, wherein the clock signal is associated with the output signal.

14. The method of claim 1, wherein no transition in value necessarily occurs immediately before the two successive data values.

15. The method of claim 3, wherein the transition in value is detected and the first compensation and the second compensation are adjusted by:

identifying a filter pattern of a plurality of pre-determined filter patterns that corresponds to the plurality of sampled data values and boundary values, each pre-determined filter pattern being associated with a particular adjustment of the first compensation applied to the first path and with a particular adjustment of the second compensation applied to the second path;

adjusting the first compensation based on the particular adjustment of the first compensation associated with the identified filter pattern; and

adjusting the second compensation based on the particular adjustment of the second compensation associated with the identified filter pattern.

16. An adaptive equalizer, comprising:

one or more equalizers configured to apply a plurality of compensation for distortion to a signal to generate an output signal;

a sampler configured to;

receive the output signal and a clock signal; and

using the clock signal, sample the output signal to generate a plurality of data values and boundary values, each value comprising either a high value or a low value based on the sampling of the output signal; and

a controller configured to;

detect a transition in value between two successive data values and determine a sampled boundary value between the two successive data values; and

independently adjust each compensation applied to the signal based at least on the high or low values of the boundary value and a plurality of data values before or after the boundary value.

17. The adaptive equalizer of claim 16, wherein an equalizer of the one or more equalizers is configured to divide the signal into parallel paths and apply the plurality of compensation for distortion in the parallel paths.

18. The adaptive equalizer of claim 17, wherein the equalizer comprises:

a divider configured to communicate a first portion of the signal on a first path and a second portion of the signal on a second path parallel to the first path;

a first one of an amplifier or a tap configured to apply a first compensation to the first path;

a second one of an amplifier or a tap configured to apply a second compensation to the second path; and

a mixer configured to combine at least the first path and the second path to compensate the signal for the distortion.

19. The adaptive equalizer of claim 17, wherein the equalizer comprises a multi-tap finite-impulse-response-filter equalizer.

20. The adaptive equalizer of claim 16, wherein the one or more equalizers comprise a plurality of equalizers that are connected in series.

21. The adaptive equalizer of claim 20, wherein a first equalizer is configured to apply a first compensation before the distortion occurs, and a second equalizer is configured to apply a second compensation after the distortion occurs.

22. The adaptive equalizer of claim 21, wherein:

the first equalizer comprises a transmitter pre-emphasis equalizer; and

the second equalizer comprises a receiver linear equalizer.

23. The adaptive equalizer of claim 18, wherein the first path comprises an unmodified signal path and the second path comprises a first-order derivative signal path.

24. The adaptive equalizer of claim 18, wherein the first compensation and the second compensation are independently adjusted based only on the high or low values of the boundary value and the plurality of data values before the boundary value.

25. The adaptive equalizer of claim 18, wherein the first compensation and the second compensation are independently adjusted based only on the high or low values of the boundary value and the two data values arriving immediately before the two successive data values.

26. The adaptive equalizer of claim 18, wherein the divider is further configured to communicate a third portion of the input data signal on a third path, the equalizer further comprising a third one of an amplifier or a tap configured to apply a third compensation to the third path, wherein:

the mixer is further configured to combine at least the first path, the second path, and the third path to compensate the signal for the distortion; and

the controller is further configured to independently adjust the third compensation applied by the third one of the amplifier or the tap to the third path based at least on the high or low values of the boundary value and the plurality of data values before or after the boundary value.

27. The adaptive equalizer of claim 26, wherein the compensation applied to the third path is decreased if:

the high or low value of the boundary value is different than the high or low value of the data value 1.5 symbols before the boundary value; and

the high or low value of the data value 1.5 symbols before the boundary value is different than the high or low value of the data value 2.5 symbols before the boundary value.

28. The adaptive equalizer of claim 16, wherein the clock signal is associated with the output signal.

29. The adaptive equalizer of claim 16, wherein no transition in value necessarily occurs immediately before the two successive data values.

30. The adaptive equalizer of claim 18, wherein the transition in value is detected and the first compensation and the second compensation are adjusted by:

identifying a filter pattern of a plurality of pre-determined filter patterns that corresponds to the plurality of sampled data values and boundary values, each pre-determined filter pattern being associated with a particular adjustment of the first compensation applied to the first path and with a particular adjustment of the second compensation applied to the second path;

adjusting the first compensation based on the particular adjustment of the first compensation associated with the identified filter pattern; and

adjusting the second compensation based on the particular adjustment of the second compensation associated with the identified filter pattern.