Amplifier pre-distortion systems and methods

1. A method of optimizing performance of a multiple path amplifier, the method comprising:

digitally processing N,N>1, input signals to generate a respective sub-signal for each of M, M>2, branches of the multiple path amplifier;

digitally pre-distorting each sub-signal using a known performance characteristic of its associated branch of the multiple path amplifier; and

supplying each pre-distorted sub-signal to its associated branch of the multiple path amplifier, wherein the multiple path amplifier comprises a combiner network for combining M amplified sub-signals from each branch to generate N output signals, and wherein digitally processing the N input signals comprises:

defining each one of the M sub-signals as a respective predetermined function of the N input signals; and

for each sub-signal, digitally processing the N input signals using the respective predetermined function.

2. A method as claimed in claim 1 , further comprising:

within each branch of the multi-path amplifier, performing a respective amplification.

3. A method as claimed in claim 1 , wherein the steps of digitally processing the N input signals to generate a respective sub-signal for each of M, M>2, branches of the multiple path amplifier and digitally pre-distorting each sub-signal are performed sequentially.

4. A method as claimed in claim 1 , wherein the steps of digitally processing the N input signals to generate a respective sub-signal for each of M, M>2, branches of the multiple path amplifier and digitally pre-distorting each sub-signal are performed as a single operation.

5. A method as claimed in claim 1 , wherein pre-distorting each sub-signal comprises, for each sub-signal, digitally processing the sub-signal using a respective set of predetermined coefficients.

6. A method as claimed in claim 5 , wherein the respective set of predetermined coefficients are adaptively computed to optimize at least one parameter of the associated branch of the multiple path amplifier.

7. A method as claimed in claim 6 , wherein the at least one parameter comprises any one or more of:

a difference between the input signal and a corresponding output signal of the multiple path amplifier;

a difference between the input signal and a corresponding amplified sub-signal within the associated branch of the multiple path amplifier;

an amplifier parameter of the associated branch of the multiple path amplifier.

8. A method as claimed in claim 7 , wherein the amplifier parameter of the associated branch comprises any one or more of an amplifier voltage, amplifier current and gate bias.

9. A method as claimed in claim 6 , wherein the respective set of predetermined coefficients are computed once.

10. A method as claimed in claim 6 , wherein the respective set of predetermined coefficients are periodically updated.

11. A digital linearizer for optimizing performance of a multiple path amplifier, the digital linearizer comprising:

a digital signal processor for digitally processing N,N>1, input signals to generate a respective sub-signal for each of M, M>2, branches of the multiple path amplifier; and

a respective pre-distorter for digitally pre-distorting each sub-signal using a known performance characteristic of its associated branch of the multiple path amplifier, an output of each pre-distorter being connected to supply a pre-distorted sub-signal to its associated branch of the multiple path amplifier wherein the multiple path amplifier comprises a combiner network for combining M amplified sub-signals from each branch to generate N output signals, and wherein the digital signal processor is configured to digitally process the N input signals by:

defining each one of the M sub-signals as a respective predetermined function of the N input signals; and

for each sub-signal, digitally processing the N input signals using the respective predetermined function.

12. A digital linearizer as claimed in claim 11 , wherein the digital signal processor and the respective pre-distorter for each sub-signal are provided as separate components.

13. A digital linearizer as claimed in claim 11 , wherein the digital signal processor and the respective pre-distorter for each sub-signal are provided as a single component.

14. A digital linearizer as claimed in claim 13 , wherein the single component comprises a Random Access memory Look-Up Table.

15. A method as claimed in claim 1 , wherein N=2 and M=3.

16. A digital linearizer as claimed in claim 11 , wherein N=2 and M=3.