A High-Efficiency Recursive Algorithm without Numerical Instability for Polynomial Predistorter Design

In this paper, based on least square estimation, a recursive algorithm for indirect learning structure predistorter is introduced. Simulation results show that of all polynomial predistorter nonlinear terms, higher order (higher than 7th-order) nonlinear terms are so minor that they can be omitted in practical predistorter design. So it is unnecessary to construct predistorter with higher order polynomials, and the algorithm will always be stable. Further results show that even when 15th-order polynomial model is used, the algorithm is convergent after 10 iterations, and it can improve out-band spectrum of 20 MHz bandwidth signal by 64 dB, with a 1.2 times 10¹¹ matrix condition number.