Advanced Digital Predistortion Algorithms for modern Base-Station Front-Ends : A physically motivated approach

Abstract

The power amplifier (PA) is the key component of the transmit chain in a mobile telecommunication system. It allows the coverage of a wide service area but it’s non-linear effects need to be compensated in order to obtain high linearity and efficiency without introducing interference on the adjacent channels. Digital Pre-Distortion (DPD) is the commonly used solution to overcome these problems. The The LTE system makes use of OFDM modulation used in modern systems, provides signals with wide bandwidth, but low average power, thus common PA designs achieve low average efficiency. Dual-input Doherty power amplifiers with digital steering introduce new degrees of freedom in terms of linearization and reconfiguration. This work analyzes the tradeoffs between linearity, efficiency and linearization bandwidth, when digitally driving the DPA inputs separately. The knowledge of the physics of the devices allows to design a workflow to linearize the dual-input DPA obtaining high efficiency and reconfigurability. In this work an application of a bio inspired optimization algorithm show how to calibrate the DPD directly at the base-station.