Granted Patent B2

US 7,957,707 · App. 11/693,897 · Granted Jun 7, 2011

Abstract

Claims (49)

1. A method for performing digital pre-distortion in a system that includes a lookup table, wherein the lookup table includes multiple lookup table entries within which lookup table gain values are storable, the method comprising:

receiving an input data sample;

identifying, based on the input data sample, a first lookup table entry of the lookup table;

updating the first lookup table entry by writing an updated gain value into the first lookup table entry; and

updating update tracking information for the first lookup table entry by updating a value stored within a first entry of an update tracking table, wherein the value indicates whether the first lookup table entry has been updated at least one time from an initial value, the update tracking table is distinct from the lookup table, and the update tracking table includes multiple update tracking table entries, each one of the multiple update tracking table entries corresponding to one of the multiple lookup table entries, and wherein updating the update tracking information includes modifying the update tracking information to indicate that the first lookup table entry has been updated.

2. The method of claim 1 , further comprising:

initializing the update tracking information to indicate that the multiple lookup table entries have not been updated.

3. The method of claim 2 , wherein initializing the update tracking information comprises:

initializing the update tracking information in the update tracking table.

4. The method of claim 1 , wherein updating the update tracking information comprises:

incrementing the update tracking information.

5. The method of claim 1 , further comprising:

initializing the lookup table by writing an initial lookup table gain value into at least some of the multiple lookup table entries.

6. The method of claim 1 , further comprising:

determining whether an adjacent lookup table entry to the first lookup table entry has not been updated; and

when the adjacent lookup table entry has not been updated, writing the updated gain value into the adjacent lookup table entry.

7. The method of claim 6 , wherein determining whether the adjacent lookup table entry has not been updated comprises:

evaluating the update tracking information corresponding to the adjacent lookup table entry.

8. The method of claim 1 , further comprising:

determining whether an adjacent lookup table entry has been updated fewer than a threshold number of times; and

when the adjacent lookup table entry has been updated fewer than the threshold number of times, writing the updated gain value into the adjacent lookup table entry.

9. A method for performing digital pre-distortion in a system that includes a lookup table, wherein the lookup table includes multiple lookup table entries within which lookup table gain values are storable, the method comprising:

receiving an input data sample;

identifying, based on the input data sample, consecutive lookup table entries of the multiple lookup table entries;

determining whether the consecutive lookup table entries have been previously updated by evaluating update tracking information stored within an update tracking table that is distinct from the lookup table, wherein the update tracking table includes multiple update tracking table entries, each one of the multiple update tracking table entries corresponds to one of the multiple lookup table entries, and the update tracking information within each of the multiple update tracking table entries indicates whether a corresponding lookup table entry has been updated at least one time from an initial value; and

performing a weighted interpolation process to produce an output gain value, wherein a previous gain value is used as at least one argument in the weighted interpolation process when at least one of the consecutive lookup table entries has not been updated.

10. The method of claim 9 , further comprising:

prior to determining whether the consecutive lookup table entries have been previously updated, initializing the update tracking information to indicate that the consecutive lookup table entries have not been updated.

11. The method of claim 9 , further comprising:

updating the consecutive lookup table entries with updated gain values; and

updating the update tracking information corresponding to the consecutive lookup table entries to indicate that the consecutive lookup table entries have been updated.

12. The method of claim 9 , further comprising:

storing the output gain value as the previous gain value.

13. The method of claim 9 , further comprising:

prior to performing the weighted interpolation process, initializing the previous gain value.

14. The method of claim 9 , further comprising:

initializing the update tracking information to indicate that the multiple lookup table entries have not been updated;

updating lookup table gain values, within the consecutive lookup table entries, by writing updated gain values into the consecutive lookup table entries;

updating the update tracking information, corresponding to the consecutive lookup table entries, to indicate that the consecutive lookup table entries have been updated;

determining whether an adjacent lookup table entry has not been updated; and

when an adjacent lookup table entry has not been updated, writing an updated gain value into the adjacent lookup table entry.

15. A digital pre-distortion apparatus adapted to pre-distort input data samples based on gain values stored within a lookup table, the digital pre-distortion apparatus comprising:

a gain value generator adapted to identify, based on an input data sample, a lookup table entry of the lookup table, to generate an output gain value based on a lookup table gain value stored within the lookup table entry, to update the lookup table entry by writing an updated gain value into the lookup table entry, and to update tracking information for the lookup table entry by updating a value stored within a first entry of an update tracking table, wherein the value indicates whether the lookup table entry has been updated at least one time from an initial value, the update tracking table is distinct from the lookup table, and the update tracking table includes multiple update tracking table entries, each one of the multiple update tracking table entries corresponding to one of the multiple lookup table entries, and wherein updating the update tracking information includes modifying the update tracking information to indicate that the lookup table entry has been updated; and

a combiner adapted to combine the input data sample with the output gain value to produce a pre-distorted data sample.

16. The apparatus of claim 15 , further comprising:

a table initialization/updating element adapted to generate gain delta values for use in calculating the update gain value.

17. The apparatus of claim 15 , wherein the gain value generator is further adapted to identify, based on the input data sample, consecutive lookup table entries of the lookup table, to determine whether the consecutive lookup table entries have been previously updated, and to perform a weighted interpolation process to produce the output gain value, wherein a previous gain value is used as at least one argument in the weighted interpolation process when at least one of the consecutive lookup table entries has not been updated.

18. The apparatus of claim 17 , further comprising:

an interpolator adapted to perform the weighted interpolation process.

Assignments (31)