Design trade-offs in signal component separators for outphasing power amplifiers

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

“…A more complex variation is asymmetric multilevel outphasing (AMO), in which there are separate amplitude signals for each PA and they can be unequal [81,86,87]. The use of a small number (typically two or four) of amplitude levels increases the complexity of the signal component separator [88][89][90], but brings a few notable advantages compared to single-level outphasing. The main benefit is the significantly improved back-off efficiency.…”