Compensation of nonlinear distortion in RF power amplifiers for wireless communications

This paper presents a new, simple and efficient technique for linearizing power amplifiers by combining iterative digital predistortion and baseband equalization. Iterative injection of in-band distortion components at baseband is applied to improve the performance of digital predistortion, whereas the equalization technique is used to minimize memory effects. The digital signal processing (DSP) algorithm is experimentally tested for a 5-MHz QPSK-modulated signal on a 751 MHz carrier amplified by a highly-efficient and highly nonlinear power amplifier. Up to 16 dB improvement in spectral re-growth is achieved by the proposed digital predistortion with 53% efficiency and with no changes to RF or modulation hardware.