Linearization of Wideband Wi-Fi Power Amplifiers Using RF Analog Memory Predistortion

Abstract

Nonlinearity of wideband power amplifiers with memory effects not only limits the performance of digital predistortion, but also challenges the hardware implementation of the digital-to-analog conversions because of the bandwidth expansion up to 5 times bandwidth of the original baseband signal after the predistortion. For wider bandwidth Wi-Fi applications such as the IEEE 802.11ac with a bandwidth of 40 or 80 MHz, PA memory effects have become more prominent and memoryless predistortion has limited effectiveness in suppressing spectral regrowth. In this paper, we improve the accuracy of a memory polynomial (MP) model for a wideband power amplifier (PA) through measurements on a 20 MHz bandwidth input signal with an interpolation method. With this MP model for the PA, an accurate RF analog MP predistorter (PD) is used to compensate both nonlinear properties and memory effects of the actual PA when the PA runs in a saturated or close to a saturated region for improving energy efficiency. The simulated results show that the performance of the MP predistortion model is robust against nonlinearity and memory effects of the actual wideband PA.