Predistortion Method for Nonlinear Distortion Cancellation in WiMAX Transmitters

A full digital linearization technique based on a predistorter scheme with a look-up table (LUT) is applied to the orthogonal frequency-division multiplexing (OFDM) transmission scheme, such as a WiMAX system. The OFDM transmission is an efficient way to deal with multipath, being its implementation less complex than traditional equalizers. This together with an efficient implementation, using the Fast Fourier Transform algorithm, has made it ideal for using in new technologies. However, it is also very sensitive to nonlinear distortions due to its greatly variable envelope and high peak to mean envelope power ratio values. The proposed method includes also a peak cancellation stage in order to reduce this problem and to improve the efficiency of the power amplifier. The method functionality has been verified by means of simulation, obtaining a reduction in the adjacent channel interference level and also an improvement in the error vector magnitude (EVM) measurement.