A multi-stage concurrent dual-band DPD architecture for closely spaced carriers using a low bandwidth feedback loop

In this paper, a novel multi-stage digital predistortion (DPD) with constrained feedback bandwidth is proposed. The proposed DPD effectively compensates for the nonlinear distortion in closely spaced multi-carrier power amplifiers (PAs). By extracting the PA static nonlinearity characteristics from the bandwidth-constrained signals and separately processing the multi-carriers input, the proposed DPD reduces the feedback bandwidth, which results in a reduction of the sampling rate. Moreover, while the DPD reduces the spectral regrowth in the adjacent channels, it effectively suppresses the spectral regrowth within the off-carrier regions along the transmission bandwidth. Experimental results have validated improved performance on a 60 MHz LTE-advanced signal, even when the analog to digital converter sampling rate is constrained to 61.44 Msps. Thus, the proposed technique can significantly decrease the difficulties in system design and reduce implementation cost.