A block-based predistortion for high power-amplifier linearization

A predistortion (PD) technique hasbeen proposed to linearize the power amplifier (PA) and improve the PA efficiency for nonconstant envelope modulation schemes. In this paper, a new PD scheme based on block estimation suitable for burst-type communications is described. The purpose of the PD is to increase the efficiency of the PA while fulfilling the error vector magnitude and spectrum mask system requirements. Piecewise (i.e., segmented) regression with continuity constraints is applied to estimate the AM/AM and AM/PM distortions. Analytical results using pth-order regression within each segment is presented. With this method, the training period is minimized. Further, the method do not suffer from bad performance during training. Simulation results with 16 quadrature amplitude modulation (QAM) show significant reduction in adjacent channel interference and considerable improvement in constellation quality for a typical class-AB high PA. The method is implemented on a harware platform containing a digital signal processor, a field programmable gate array, a modulator, and a 1.6-GHz class-AB PA. Experimental results with a 16-QAM modulated signal and a symbol rate of 151.2 kHz are presented.