2004 Volume 17 Issue 1 Pages 48-56
In this paper, an adaptive predistortion scheme is proposed to compensate nonlinearity of high power amplifiers (HPA) in OFDM systems. A complex Wiener model is adopted to describe the input-output relationship of HPA, where a linear dynamics is followed by a memoryless nonlinear static element approximated by using complex power series expression. In order to compensate the linear and nonlinear distortions in the HPA, a predistorter (PD) is constructed by directly adjusting a Hammerstein model which is an inverse of HPA. To update parameters of the PD, an efficient adaptive identification algorithm using real number calculation is given. Furthermore an adaptive algorithm updating the parameters in every one symbol-interval is also developed in the frequency-domain. The effectiveness of the proposed adaptive schemes is validated by numerical simulations treating HPA in 64QAM-OFDM transmitter.