Implementation of an adaptive digital/RF predistorter using direct LUT synthesis

This paper proposes an integrated adaptive digital/RF look-up-tables (LUT) based predistorter for the linearization of RF power amplifiers (PA). The LUT content that feeds a linear vector modulator used for the realization of the inverse nonlinear function is directly deduced given baseband input and output signals of the PA. Measured output spectrum of a linearized 90-W peak LDMOS power amplifier reveal a significant reduction of the power emission at the adjacent channels of about 15 dB under IS95, single-carrier WCDMA. The noteworthy experimental results carried out in this work were obtained through the construction of a prototype using an envelope detector, a linear RF vector modulator, FPGA, DSP processors, and fast A/D and D/A converters.