2-D Digital Predistortion Using Vector Quantization Method for Dual-Band Transmitters

Abstract

This paper proposes a two-dimensional (2-D) digital predistortion (DPD) technique using vector quantization piecewise (VQP) method to compensate for nonlinearities of power amplifiers (PAs) in concurrent dual-band wireless transmitters. 2-D DPD architecture is used to extract the predistortion coefficients and linearize the PA in each band separately, which results in lower sampling rates of digital-to-analog and analog-to-digital converters compared to traditional 1-D method. Vector quantization method is introduced to divide the 2-D signal space into several regions in terms of signal amplitude probability distribution and subtle 2-D memory polynomial (MP) models are assigned to the regions, thus the proposed technique can linearize the PA in the whole signal amplitude range successfully due to the fact that PA nonlinearities are usually dependent on amplitude modulation characteristics strongly. The performance of dual-band wideband code division multiple access (WCDMA) signals which are 100 MHz apart is investigated. The simulation results show that when the region number is 16, 2-D VQP DPD implement can improve the PA's adjacent channel power ratio (ACPR) by about 13dBc, and it is 8 dB better than the 2-D PDD method.