A practical FPGA-based LUT-predistortion technology for switch-mode power amplifier linearization

In the context of wireless communications, power amplifiers raise a number of issues. Mastering the linearity vs. efficiency trade-off is not trivial. Switch-mode power amplifiers can provide high power efficiency. However, they exhibit significant nonlinearities, which make them difficult to apply in modern high linear modulation wireless systems. In order to enable their use in such systems, a LUT-based predistortion technique targeting switch-mode PA linearization is introduced. Particularly the predistortion function derivation for handling the whole input interval of the nonlinearity predistortion is described. A 0.18µm CMOS Class F power amplifier is used as the study-case for testing and evaluating the proposed approach. Matlab and DSP-Builder blocks targeting a Stratix II FPGA simulation results show that the proposed LUT-based predistortion technique effectively improves the linearity of the switch-mode PA with an average EVM of less than 2%.