To improve the accuracy of the nonlinear distortion correction for the radio frequency (RF) power amplifier (PA), it is necessary to precisely obtain the reverse function of the PA nonlinear model. However, the direct inversion of the PA nonlinear model involves solving a high-order univariate polynomial, which is difficult to apply in engineering. In this study, based on the envelope memory polynomial (EMP) model, the high-order terms of the nonlinear model are approximated by their previously calculated values through iterations and considered as known constants in the polynomial solution finding process, thereby resulting in a significant reduction in computational complexity. Compared with the direct inversion method, model of a 9th-order nonlinear, the proposed method reduces the calculation time in the coordinated rotation digital computer (CORDIC) algorithm by at least 80%. The simulation results show that for a long-term evolution (LTE) downlink signal, the results obtained by the proposed simplified method agree well with those obtained by direct inversion method.
digital predistortion power amplifier nonlinear distortion memory effects radio frequency
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This work was supported in part by National Natural Science Foundation of China (Grant Nos. 61771107, 61701075, 61771115, 61531009, 61471108), National Major Projects (Grant No. 2016ZX03001009), the Project Funded by China Postdoctoral Science Foundation, and the Fundamental Research Funds for the Central Universities.
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