RF Subsampling Feedback Loop Technique for Concurrent Dual-Band PA Linearization

This paper investigates feedback loops using radio-frequency (RF) subsampling analog-to-digital converters as a way to improve the concurrent dual-band transmitters linearization. The feedback loop will be characterized and post compensated in the digital domain, followed by a new technique for a concurrent dual-band digital predistortion (DPD) scenario where aliasing between both the carriers is allowed to occur. The proposed technique is based on statistical approximated nonoverlapped multisines that permit relaxing the feedback loop requirements. The measurement results in a 2-D-DPD scenario are presented and compared with other state-of-the-art techniques. Metrics such as adjacent channel power ratio and error vector magnitude are evaluated in order to corroborate the correct functioning of the proposed technique.