Application of RLS Algorithm in Baseband Predistortion Systems

The traditional predistortion algorithm based on Least Squares(LS) algorithm needs large amount of computations,and cannot keep up with the change of the characteristic of the Power Amplifiers(PAs) adaptively.This paper derives the baseband predistortion algorithm based on the Recursive Least Squares(RLS) algorithm and indirect learning structure,and simulates and analyses the performance of the algorithm.The simulation results indicate that the algorithm works as good as the traditional predistortion algorithm based on LS algorithm in compensating the nonlinearity of the PA.For validating the algorithm,a HF(High Frequency) transmitter with predistortion function is designed and built.The hardware test results show that the 3rd intermodulation component of the output of the PA is improved 25 dB after applying the baseband predistortion algorithm,and all the intermodulation components are under-53 dB.