Real-time digital predistortion for radio frequency power amplifier linearization

Abstract

In this paper, a system is proposed for real-time calculation of digital predistortion (DPD) coefficients to linearize wideband radio frequency (RF) power amplifiers (PAs). The proposed system leverages the commercially available National Instruments (NI) PXIe-5646R vector signal transceiver (VST) platform. The VST is a single module RF instrument that combines a 200MHz instantaneous vector signal analyzer (VSA) and vector signal generator (VSG) with a shared Xilinx LX240T field-programmable gate array (FPGA). The FPGA is used to perform look-up table (LUT) predistorter estimation and predistortion in real-time. The proposed system is shown to reduce the time to generate a predistorted waveform by over two orders of magnitude compared to a software implementation. Furthermore, the linearity achieved with the proposed FPGA implementation closely matches a traditional software-based approach, with 15dB improvement in adjacent channel leakage ratio (ACLR) and a 3x improvement in error vector magnitude (EVM) for a 3G mobile handset power amplifier.