Modulation agnostic digital hybrid mode power amplifier system and method

A digital predistortion system for linearizing the output of power amplifiers comprising:

• an input configured to receive an input signal for wireless communications;
• at least one power amplifier for outputting an amplified signal;
• a feedback path including at least one feedback signal derived from the amplified signal, wherein the at least one feedback signal includes a representation of a noise characteristic of the power amplifier;
• digital predistortion logic for predistorting the input signal and supplying a predistorted signal to the at least one power amplifier, wherein the digital predistortion logic complies at least in part with the equation:
• z
• ⁡
• (
• n
• )
• =
• ∑
• i
• =
• 0
• n
• -
• 1
• ⁢
• x
• i
• ⁡
• (
• n
• -
• i
• )
• ⁢
• (
• ∑
• j
• =
• 0
• k
• -
• 1
• ⁢
• a
• ij
• ⁢
• 
• x
• i
• ⁡
• (
• n
• -
• i
• )
• 
• j
• )
• ,
• where z(n) is a predistortion function, n is a variable representing time, xt is a transmission (input) signal, i, j, and k are counters for summation, N is a number of data per block, and aij are predistortion coefficients;
• delay estimation logic configured to estimate the delay between the input signal and the feedback signal by maximizing an amplitude difference correlation of the input signal and the feedback signal, wherein the delay estimation logic selects between an integer delay when the amplitude difference correlation is odd and between a fractional delay when the amplitude difference correlation is even;
• a memory for storing the predistortion coefficients;
• estimator logic configured to determine the predistortion coefficients, wherein the estimator logic includes a least square algorithm, and wherein the predistortion coefficients are based at least in part on the estimated delay;
• and
• a multiplexor configured to receive the predistortion coefficients from the memory and configured to receive the predistortion coefficients from the estimator logic, wherein the multiplexor selects either the predistortion coefficients received from the memory or the predistortion coefficients received from the estimator logic, and wherein the multiplexor supplies the selected predistortion coefficients to the digital predistortion logic.