Design of a fifth-order analog predistorter for base station HPA of cellular mobile systems

Abstract

This article presents the design of a fifth-order analog predistorterfor use in base station high power amplifiers (HPA). The predistorter employs two intermodulation (IM) signal generators with identical configuration, to individually generate the third- and fifth-order (IM3 and IM5) signals. The amplitudes and phases of the two IM signals generated are adjusted separately for cancellation of the third- and fifth-order intermodulation distortion products (IMDP3 and IMDP5) at the HPA output, making the tuning process of predistortion much easier. The predistorter is designed and studied by computer simulation, using two-tone and π/4-DQPSK signals, centered at 2.2 GHz in a practical base station 100 W HPA. For verification of the design, measurements are carried out on a prototyped-predistorter. Both simulation and measurement results show that very good agreement and excellent linearity improvement of the HPA can be achieved at an output power of 65.6 W.