Adaptive predistortion technology based on piecewise nonlinear function

The paper proposes a digital adaptive predistortion approach to compensate the nonlinear distortion caused by a high-power amplifier (HPA). The predistortion scheme adopted is based on the bilinear rational function's property that it is a nonlinear function which can be well employed to approximate HPA's AM-AM or AM-PM nonlinear function, and its inverse function can be easy to calculate. We quantize the region of input amplitudes uniformly, and employ an estimator to evaluate the nonlinear characteristic curve of the HPA by using a piecewise bilinear rational function. To achieve the predistortion compensation, we adjust the nonlinear parameters of the predistortor by training the parameters of the estimator. The performance of the proposed algorithm is assessed through computer simulation in the orthogonal frequency division multiplexing (OFDM) system.