A 2D Rapidly-Convergent Iterative Digital Predistortion Method Using Direct Learning Structure

This paper presents a two-dimensional (2D) digital predistortion (DPD) algorithm, which models the power amplifier (PA), inverses the identified model and calculates the predistortion coefficients with an iterative approach. The method is applied to compensate for the nonlinear distortion of in-band and cross-band modulation in concurrent dual-band transmitters. Experimental measurements were carried using a dual-band OFDM signal with center frequencies of -40MHz for the lower band and 40MHz for the upper band. The predistortion results demonstrate that the algorithm converges after the third iteration, and the adjacent channel power ratio (ACPR) and the normalized mean square error (NMSE) are reduced 19dB and 22dB respectively.