A novel digital predistorter compensating for even order distortions of concurrent multiband power amplifiers with a single common feedback loop

This paper proposes a novel scheme of digital predistorter (DPD) that can concurrently compensate for both the odd-order distortions and the even-order distortions for concurrent multi-band power amplifiers (PAs) at low super high frequency (SHF) and high SHF bands with a single common feedback loop; the odd-order distortions occur at low and high SHF bands as well-known nonlinear distortions, and the even-order distortions occur at a frequency equal to the difference between low and high SHF bands and at a frequency twice as high as that of low SHF band. The proposed DPD utilizes a single common feedback loop in order to provide a feedback signal that includes the odd-order and the even-order overlapped feedback signals for adaptive DPDs. The proposed single common feedback architecture significantly reduces complexity, size and power consumption for DPD circuits. Additionally, the proposed DPD also separates the even-order overlapped feedback signal successfully. The presented experimental results show that the proposed DPD scheme reduces analog circuit complexity and size, and achieves 50 % reduction of power consumption in the feedback loop without sacrificing the DPD linearization performance.