A fast convergence digital pre-distortion of APSK modulations based on joint algorithm

To compensate the nonlinear distortion of signals when high level APSK modulations is applied to satellite communication systems, a fast convergence memoryless digital pre-distortion algorithm is proposed. Based on the Saleh model of satellite high power amplifier (HPA), a joint algorithm for the adaptive parameter estimation is adopted which combines the normalized least mean square (NLMS) and recursive least square (RLS) algorithm. At the beginning of adaptive process RLS is used, and LMS is used when errors are reduced to a certain degree, and hence the factors of HPA models are calculated fast and accurately. Simulations results show that this algorithm converges fast and gets small steady state errors.