Will Doherty continue to rule for 5G?

High data rate 5G systems are expected to operate at frequencies between 15GHz and 100GHz, and utilize large numbers of antennas in both base-stations and handsets. Representative power amplifier scenarios differ from those in commercial wireless today: there will be many more power amplifiers operating at much low power levels. Yet signal peak-to-average ratios will remain high, and efficiency will remain a critical consideration. Doherty amplifiers will be a prime contender for these applications, although they are not the only possibility. This paper reviews the emerging requirements for power amplifiers in mm-wave 5G systems, describes the status of mm-wave Doherty ICs in different device technologies, lists challenges for amplifier designs, and provides a glimpse of approaches other than Doherty amplifiers to meet the needs.