Improved Digital Predistortion for Concurrent Multiband Transmission Using Frequency Relocation

In concurrent multiband settings with large carrier spacings between bands, digital predistorter (DPD) implementations face the issue of how to linearize a sparse signal spectrum spanned over large bandwidths at low computational complexity. Frequency relocation is one possible approach that involves relocating baseband carriers to have reduced frequency spacing with the help of band-limiting functions, to yield a denser and smaller signal bandwidth for the DPD to linearize. In this letter, frequency relocation for transmitters with frequency-varying gain and phase is explicitly considered. It is shown that band-wise preequalization during frequency relocation can reduce the computational complexity for a certain allowed in-band error.