A Quadratic-Interpolated LUT-Based Digital Predistortion Technique for Cellular Power Amplifiers

Baseband digital predistortion (DPD) is an efficient and low-cost method for linearizing a power amplifier (PA) in a wireless system using a modulation scheme with nonconstant envelope. The polynomial and the lookup table (LUT) predistortion schemes are two commonly used approaches. Both approaches require time to find the inverse characteristics of the PA to be predistorted. However, for DPD to be actually implemented in real-world scenarios, fast convergence is highly desirable. A low-complexity joint-polynomial/LUT predistortion PA linearizer is proposed to obtain fast linearization. The algorithm utilizes quadratic interpolation of the LUT, which reduces the required LUT size and hence reduces convergence time without degradation of linearity. Simulation result shows that the proposed method can achieve up to 500% improvement in convergence speed compared with the conventional linear interpolation approach for the wideband code-division multiple access application.