Dual-Band Volterra Series Digital Pre-Distortion for Envelope Tracking Power Amplifiers

Abstract

This letter presents a new dual band Volterra-based model suitable for the linearization of envelope tracking (ET) power amplifiers (PAs) driven concurrently with two widely spaced modulated signals. The model has two modules: a dual-band baseband equivalent Volterra series to compensate for the dynamic nonlinear distortions associated with the PA (assuming a constant drain supply voltage) and a polynomial term added to mitigate the distortions introduced by a dynamic drain supply modulation. The proposed model was successfully applied to linearize a $10~{\rm W}$ and a $45~{\rm W}$ dual band ET PA concurrently driven with different arrangements of two signals modulated according to wideband code division multiple access and long-term evolution standards around $2.0$ and $2.2~{\rm GHz}$ , and $2.1$ and $2.9~{\rm GHz}$ . A measured error vector magnitude of 1.5% and an adjacent channel power ratio better than $-47~{\rm dBc}$ , demonstrated the excellent linearization capacity of the proposed dual-band ET Volterra digital pre-distortion scheme.