Power amplifiers (PA) always exhibit some degree of non-linearity, and the higher linearity products are much more expensive. The Lime Adaptive Digital Pre-Distortion (ADPD) core allows tight transmitter specifications to be met using a lower cost PA, by correcting the non-linear operation. In the case of radio frequency (RF) PAs, linearization also improves power efficiency and subsequently reduces the running cost of the wireless infrastructure.
Considering the PA performance for a given air interface, adjacent channel power ratio (ACPR) and error vector magnitude (EVM) are the key considerations to provide support for sophisticated modulation schemes, multi-carrier signals, and high modulation bandwidths.
Lime Microsystems fully open source solution for PA linearisation is based on adaptive digital pre-distortion (ADPD). The FPGA RTL and host software sources can be found on GitHub. For more in-depth technical details, please see the wiki page.
LimeADPD is supported on the LimeSDR QPCIe board, and the LimeNET Base Station which provides a fully integrated hardware solution complete with a powerful Intel Core i7-6950X based host, power amplifiers and duplexers.