Research On Pre-distortion Algorithm Of Satellite Communication Power Amplifier

With the rapid development of the satellite communication industry,high efficiency modulation technology and high power amplifier are widely used in communicated system.However,there would be serious distortion when modulated signal with non-constant envelope and high peak-to-average power ratio passes through the high efficiency power amplifier,such as in band distortion and out of band distortion.In band distortion is amplitude and phase distortion of signal?which would increase bit error rate.Out of band distortion would result in spectral expansion,adjacent channel interference and lower spectral efficiency.The use of pre-distortion to improve the linearity of power amplifier while ensuring the efficiency of power amplifier is a hot spot for the linearization of power amplifier.In this paper,adaptive algorithm and corresponding improvement strategy for digital baseband pre-distortion system is mainly studied.The digital arrangement is as follows:(1)In this paper,traditional adaptive algorithms based on memory polynomial for Digital baseband pre-distortion are well investigated,and a new adaptive step-size LMS algorithm named GN-LMS is proposed,which has better convergence speed and accuracy.(2)Based on the research and contrast of the traditional LMS algorithm and RLS algorithm,some complementary in terms of advantages and disadvantages between LMS algorithm and RLS algorithm have be found.Through the judgment of switching mode,GN-LMS algorithm and RILS algorithm can be integrated into a new judgment selection algorithm which combines the advantages of the two algorithms,and the effectiveness of the proposed algorithm is verified in the simulation of pre-distortion system.(3)Based on the research of classical adaptive CNGD and CRTRL algorithm in complex domain,an N-AACRTRL algorithm based on PRNN is proposed.PRNN network model can effectively reduce the matrix dimension and computational complexity,and adaptive amplitude is introduced to improve the convergence of the algorithm.At the same time,iterative Gauss-Newton algorithm is used for the updating of weight matrix,in which the second derivative is added and the matrix inversion procedure is simplified.To some extent,the convergence speed of PRNN based N-AACRTRL algorithm is improved.Pre-distortion simulation shows that PRNN based N-AACRTRL algorithm can compensate the nonlinearity of the system and suppress adjacent channel expansion effectively.