WCDMA outphasing power amplifier with a software defined transmitter/receiver architecture for determination of the predistortion function
A flexible and easily configurable software defined transmitter/receiver (TX/RX) architecture is described, which allows the determination of the distorted complex transfer characteristics of a 3 port nonlinear outphasing power amplifier (PA) for application in a WCDMA base station. The TX/RX architecture is capable of generating high precision single sideband signals (SSB) using a DSP algorithm, which is almost insensitive to measurement errors and to the frequency response of the output measurement channel. Based on this an inverse predistortion function for a necessary linearization is calculated and implemented into a FPGA (field programmable gate array) through look-up-tables (LUT). The common base band and the differential phase angles are predistorted, resulting in a linearization of the PA.