Digital Pre-distortion Amplifier In The Adaptive Algorithm

Predistortion is a promising technique to linearize power amplifiers. It uses a pre-distortion device whose amplitude and phase characteristics are opposite the amplifier's to revise amplifier's nonlinear distortion. After reading much literature, this paper does some research work on the predistortion technology, mainly in the research of the adaptive algorithm. The main contents are as follows:1. Several kinds of power amplifiers'modeles are described.2. The principles of predistortion techniques are described. The mainly research work is on the realization of the look-up-table based predistortion.3. Improving LMS algorithm. There is only one parameter needed to determine its scope, so this new algorithm has simple form and is convenient to use. Through theoretical analysis, it shows that the new algorithm is stable and the mean convergence and mean square convergence are proved by use of series convergence principle. Simulation shows the new algorithm converges faster than LMS algorithm and improved SVSLMS algorithm.4. Improving normalized LMS algorithm. The new algorithm normalizes the input signal and uses the function which have forgetting factor, in order to improve the convergence it also adds a parameter to control the initial step size. Through theoretical analysis, new algorithm is proved to be stable and convergent. Simulation shows the new algorithm converges faster than normalized LMS algorithm.5. The basic principles of RLS algorithm and affine projection algorithm are described. It uses these two algorithms in the simulation of the predistortion amplifier. The simulation has good results.