An FPGA-based technique for linearizing RF power amplifiers

In this paper, an efficient predistortion method for linearization of RF power amplifiers is proposed. In this technique, appropriate signals are added to the main baseband input signal to reduce the nonlinearity of the PA. The non-linear relationship between input and output of an RF PA is analyzed and optimum values for the injection signals at the intermodulation frequencies are obtained. In addition, a high-speed low-cost MATLAB-FPGA interface is designed that can be used both in the training and testing phases of the system. Simulation results indicate that the proposed technique is capable of remarkably reducing spectral regrowth in adjacent channels for different non-constant envelope signals. Using a QPSK signal, the spectral regrowth and ACPR of the PA are decreased by 20dB and 26dB, respectively.