Experimental Proof of Concept Applying Digital Predistortion to Radio Frequency Power Amplifiers

Abstract

The non-linear behavior of amplifiers of power in wireless communications systems, introduces a lateral spectral growth that compromises efficiency in power and spectral. This article presents a numerical validation and experimental implementation of digital predistortion system to mitigate the adjacent channel power ratio (ACPR) impact of power amplifier applications in the 0.9 GHz band with power gains of up to 14 dB. Applying the Saleh model from the curves of amplitude-modulation (AM) and phase-modulation (PM), and modelling the inverse transfer function in an implementation under GNU Radio environment, it was possible to provide a mitigation of the ACPR. The experimental result allows to make a proof-of-concept of digital predistortion showing a reduction in ACPR of 8 dB for a baseband wireless transmission system using N210 USRP modules and transmitting in base band using QPSK modulation format at 100 kS/s.