13.7 A 0.23mm² digital power amplifier with hybrid time/amplitude control achieving 22.5dBm at 28% PAE for 802.11g

Multilevel outphasing power amplifier system with a transmission-line power combiner

“…As a method of applying the amplitude modulation, analog-intensive supply modulation [31,32] has been increasingly replaced by various structures labeled as digital PAs (DPAs), which can modulate the output amplitude directly based on a digital signal. These include switched-capacitor PAs [33][34][35][36][37][38][39][40] and PAs consisting of parallel current-mode cells [41][42][43][44][45]. As the description above reveals, the polar architecture enables highly digital implementation, in which all signals are fully digital or time-mode up to the PA inputs.…”