Systematic Design of High Efficiency Doherty and Outphasing PA from Load-Pull Data
Doherty and Chireix outphasing have emerged as two of the most promising architectures to enhance the efficiency of power amplifiers with amplitude-modulated signals. Although their original principles promise outstanding efficiency characteristics, non-ideal transistor behavior, parasitics and combiner losses severely limit the performance in practical RF and millimeter-wave applications. Intense research has therefore resulted in numerous extensions and revisions of the original combiner topologies to counteract these effects.
This talk will present an alternative systematic design approach for Doherty and outphasing PAs where conventional combiners are replaced by black-box networks that are synthesized directly from transistor load-pull data using analytical expressions. The effects of transistor nonidealities, parasitics, and impedance matching are thereby absorbed into a single compact combiner network. The result is not only superior efficiency and a compact layout, but also new degrees of freedom in the design space. Several GaN and SiGe PA design examples will be presented to illustrate its use in wireless communication transmitters.