Analysis of different predistortion structures and efficient least-square adaptive algorithms

Adaptive predistortion is one of the most promising techniques to overcome the nonlinearity of high power amplifier (HPA). However, the adaptation of the predistorter is not satisfied, for many efficient least-square (LS) adaptive algorithm cannot be used. We analyze previously published predistortion structures and their difficulties in adapting with these efficient algorithms. The proposed structure constructs the desired output of the predistorter, so many efficient LS adaptive algorithms can be used directly, which implies that we can obtain faster convergence and lower complexity in adaptive process. Simulation results using the recursive least square (RLS) algorithm in adaptation demonstrate about 30 dB spectrum spreading improvement.