Digital RF and digitally-assisted RF (invited)

One of the most important developments in the wireless industry within the last decade was the digitization of RF circuitry. This was in response to the incredible advancements of the mainstream CMOS technology in both processing speed and circuit density, as well as the relentless push to reduce total solution costs through integration of RF, analog and digital circuitry. Since the digital baseband part of a wireless communication channel has been traditionally implemented in the most advanced CMOS technology available at a given time for mass production, the need for single-chip CMOS integration has forced permanent changes to the way RF circuits are fundamentally designed. In this low-voltage nanometer-scale CMOS environment, the high-performance RF circuits must exploit the time-domain design paradigm and heavily rely on digital assistance. This paper revisits the digitization journey of RF circuits.