Time-alignment of two signals used for digital pre-distortion
View Patent ↗A digital pre-distortion system which can provide the flexibility to model the highly non-linear distortion associated with High Efficiency RF Power Amplifiers while through a novel implementation of a least squares estimation process allows an implementation well suited for an FPGA application where limited resources and in particular memory resources are available.
1. A method comprising:
calculating a whole sample time variance between two signals captured by a capture block of an amplifier distortion adjustment facility to determine an accuracy of alignment of the two signals;
digitally whole sample time-shifting at least one of the two signals relative to the other signal to coarsely minimize the variance; and
interpolating at least one of the two signals to facilitate digitally time-shifting the at least one of the two signals to finely minimize the variance.
2. The method of claim 1 , wherein interpolating includes passing the at least one of the two signals through a FIR filter structure.
3. The method of claim 2 , wherein the FIR filter structure includes a separate set of coefficients for each of a plurality of fine offset values.