Digital predistortion based on envelope feedback

A new digital predistortion (DPD) technique based on envelope feedback is proposed for linearization of power amplifiers (PAs). Unlike conventional DPD techniques that need frequency down converters (FDCs) in the feedback path to recover the complex envelope of the PA output, the proposed technique does not need an FDC. Instead it employs two envelope detectors, estimating the envelope of the PA output and that of the difference signal between the PA input and the PA output. It is shown that the complex envelope of the PA output can be estimated from the two envelope feedbacks if the sign of the phase distortion of the AM-PM characteristic remains the same for all PA input magnitudes. Simulation results show that the performance of the proposed DPD is comparable to the conventional DPD employing an FDC.