Crest Factor Reduction of Inter-Band Multi-Standard Carrier Aggregated Signals

This paper proposes an effective solution for the crest factor reduction (CFR) of inter-band carrier aggregated signals composed of multiple widely spaced component carriers (CC). This solution embeds a peak estimator, which determines the amount of clipping to apply to the instantaneous samples of the individual CCs. The resulting CFR runs at a sampling rate proportional to the bandwidth of the constituent CCs and is not impacted by the frequency spacing between them. This allows for a significant decrease in the computational complexity and power overhead associated with classical CFR techniques that need to operate at much higher sampling rates. The proposed CFR solution is extended to address carrier aggregation scenarios of unequal power levels, different error vector magnitude requirements, and an arbitrary number of CCs. Finally, the proposed CFR approach and a multi-band digital-predistortion scheme are jointly applied to assess their impacts on RF power-amplifier demonstrators driven with multi-standard carrier aggregated waveforms composed of two or three long-term evolution and wideband code-division multiple-access CCs.