Amplifier pre-distortion systems and methods

Abstract

A method of optimizing performance of a multiple path amplifier includes: splitting an input signal to derive a respective sub-signal for each branch of the multiple path amplifier; independently 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 amplifier.

1 . A method of optimizing performance of a multiple path amplifier, the method comprising:
 digitally processing an input signal to generate a respective sub-signal for each branch 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.   
   
   
       2 . A method as claimed in  claim 1 , wherein the steps of digitally processing the input signal to generate a respective sub-signal for each branch of the multiple path amplifier and digitally pre-distorting each sub-signal are performed sequentially. 
   
   
       3 . A method as claimed in  claim 1 , wherein the steps of digitally processing the input signal to generate a respective sub-signal for each branch of the multiple path amplifier and digitally pre-distorting each sub-signal are performed as a single operation. 
   
   
       4 . A method as claimed in  claim 1 , wherein the steps of digitally processing the input signal to generate a respective sub-signal for each branch of the multiple path amplifier and digitally pre-distorting each sub-signal comprise:
 defining a respective portion of the input signal corresponding to each sub-signal;   pre-distorting each of the defined portions of the input signal, using the known performance characteristic of its associated branch of the multiple path amplifier; and   supplying each of the predistorted portions of the input signal to the respective branches of the multiple path amplifier.   
   
   
       5 . A method as claimed in  claim 1 , wherein digitally processing the input signal comprises:
 comparing the input signal to a predetermined threshold; and   splitting the input signal into a corresponding first sub-signal and a second sub-signal based on the comparison result.   
   
   
       6 . A method as claimed in  claim 5 , further comprising periodically adjusting a value of the predetermined threshold. 
   
   
       7 . A method as claimed in  claim 1 , wherein digitally processing the input signal comprises splitting the input signal into a corresponding first sub-signal and a second sub-signal such that respective power levels of the first sub-signal and the second sub-signal satisfy a predetermined relationship. 
   
   
       8 . A method as claimed in  claim 7 , wherein the predetermined relationship is equality between the power levels of the first sub-signal and the second sub-signal. 
   
   
       9 . 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. 
   
   
       10 . A method as claimed in  claim 9 , 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. 
   
   
       11 . A method as claimed in  claim 10 , 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.   
   
   
       12 . A method as claimed in  claim 11 , wherein the amplifier parameter of the associated branch comprises any one or more of an amplifier voltage, amplifier current and gate bias. 
   
   
       13 . A method as claimed in  claim 10 , wherein the respective set of predetermined coefficients are computed once. 
   
   
       14 . A method as claimed in  claim 10 , wherein the respective set of predetermined coefficients are periodically updated. 
   
   
       15 . A method as claimed in  claim 1 , wherein the multiple path amplifier comprises M, where M>2, branches for amplifying M corresponding sub-signals, and a combiner network for combining the M amplified sub-signals from each branch to generate N, where N>1, output signals, and wherein digitally processing the input signal comprises:
 defining each one of the M sub-signals as a respective predetermined function of N input signals; and   for each sub-signal, digitally processing the N input signals using the respective predetermined function.   
   
   
       16 . A digital linearizer for optimizing performance of a multiple path amplifier, the digital linearizer comprising:
 a digital signal processor for digitally processing an input signal to generate a respective sub-signal for each branch 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.   
   
   
       17 . A digital linearizer as claimed in  claim 16 , wherein the digital signal processor and the respective pre-distorter for each sub-signal are provided as separate components. 
   
   
       18 . A digital linearizer as claimed in  claim 16 , wherein the digital signal processor and the respective pre-distorter for each sub-signal are provided as a single component. 
   
   
       19 . A digital linearizer as claimed in  claim 18 , wherein single component comprises a Random Access memory Look-Up Table.