US Patent 7385447 Power amplifier having curve-fitting predistorter

A power amplifier has a plurality of amplifier stages. One or more predistorters are each placed between amplifier stages within the power amplifier path. The predistorters set breakpoints in a predistortion curve and divide the predistortion curve into a plurality of segments. Each predistorter may be adjusted to change the slope of each segment. This adjustment forms a piecewise curve-fit to approximate the inverse of the amplifier transfer characteristic. The curve-fit can be made arbitrarily close to the amplifier transfer characteristic by the selection of a sufficient number of breakpoints and therefore a sufficient number of predistortion curve segments, leading to a satisfactory linearization of the power amplifier.