Error sensitivity in adaptive predistortion systems

Digital baseband predistortion is a well known technique to compensate for AM/AM and AM/PM amplifier nonlinearity. The practical implementation of a flexible digital predistorter suggests introducing some adaptation strategy to the predistortion technique in order to take count of the changes in the nonlinear characteristics due to ageing, temperature or channel switching of the amplifier. The most effective adaptation criterions, are generally based on the estimation of the residual nonlinear distortion at the output of the predistorted amplifier. A simple criterion is to compare the amplifier output with the predistorter input. This comparison requires an estimation of the input-output time delay of the amplification chain. The aim of this work is to analyse the sensitivity of the adaptation algorithm to errors in the time delay estimation and to noise sources like quantization and intersymbol interference