An adaptive predistortion method for linear power amplifiers

A basestation power amplifier requires high linearity and stable operation for common amplication of a multiplexed wideband signal. Nonlinearity compensation techniques with feedforward or a predistorter are useful for this purpose. This paper presents a predistortion amplifier with automatic control at RF band for application at a basestation. In this method, the predistorter distorts an RF input signal by referring to a look-up table (LUT) corresponding to the input power. Out-of-band radiation power are directly monitored at the IF band to determine the LUT. A DSP with an iterative algorithm updates the content of the LUT to minimize the out-of-band radiation power. A computer simulation experiment is carried out. Out-of-band spectral density is suppressed below -80 dB. This predistorter can cope with imperfect characteristics of the device used in the predistorter