Implementing crest factor reduction (CFR) by offsetting digital predistortion (DPD) coefficients

A combined approach to digital predistortion (DPD) and crest factor reduction (CFR) is proposed. The new CFR is structured similar to DPD and is implemented by introducing a steady-state offset into the DPD coefficients. The DPD and CFR coefficients are estimated using separate adaptive processes but applied to the transmission path in a common module. Results show that CFR lowers the PAPR of the predistorted signal by 5 dB, which reduces the stress on the peaking transistor in a Doherty PA.