An Approximation of Volterra Series Using Delay Envelopes, Applied to Digital Predistortion of RF Power Amplifiers With Memory Effects

In this letter, a new model for digital predistortion (DPD) of radio frequency power amplifiers for wide-band applications is proposed. The model is based on a spline approximation of Volterra series by considering second-order cross-terms. The advantage of the spline cross-term model is a reduction in the number of model parameters. We further reduce the model order by operating on delayed envelope samples, rather than the complex baseband samples. A block of wide-band code-division multiple access signal is sent through a 90 W class-AB power amplifier, based on the freescale LDMOS output device, and the input/output baseband samples were used to identify the DPD parameters.