Patent ID: 7733978

Claim:
An apparatus of dynamically adapting a look up table (LUT) spacing for linearizing a power amplifier (PA), in order to produce an amplified output signal in response to a predistorted input derived from an input modulated signal v m , said apparatus comprising: a size-N LUT containing N entries, which divides a whole unsaturated PA input amplitude range into N bins, each of said LUT entries corresponding to an input amplitude predistorted by the entries of said LUT, N being a positive integer; an index mapper, via which said LUT is indexed by an input amplitude r m of said input modulated signal to implement an unconditionally non-uniform LUT spacing; and a spacing adaptor, which online adapts said LUT spacing, said adapted LUT spacing balancing inter-modulation distortion (IMD) power at a PA output corresponding to each bin so that total IMD power at said PA output is minimized; wherein said spacing adaptor adapts said LUT spacing based on a histogram-based predistortion method derived from processing histograms of a plurality of input modulated signals using an online iterative procedure including the steps of: initializing bin boundaries of said LUT and an iteration index k, and assigning a midpoint of each said bin; estimating a long-term histogram for said plurality of input modulated signals; updating N bin widths {d i }, for i from 1 to N; waiting until all entry values in said LUT have been renewed; and checking if a difference of said LUT spacing between a current iteration and a previous iteration is convergent.