Digital Radio-Frequency Transmitters: An Introduction and Tutorial

There has been a long fascination with digitizing a radio-frequency (RF) power amplifier (PA). Part of this momentum is due to the relentless pace of Moore's law scaling in past decades. Digital gates are cheaper than ever, so why can't RF PAs take advantage of digital gates? Complementary metal-oxide-semiconductor (CMOS) inverters are very efficient amplifiers that require no bias current or large inductors. So it seems that digitizing the PA not only results in great efficiency but also a small silicon footprint. Yet designing an RF PA is not only about getting the best efficiency but also about how to do so linearly.