Theory and Implementation of RF-Input Outphasing Power Amplification

Conventional outphasing power amplifier systems require both an RF carrier input and a separate baseband input to synthesize a modulated RF output. This work presents an RF-input / RF-output outphasing power amplifier that directly amplifies a modulated RF input, eliminating the need for multiple costly IQ modulators and baseband signal component separation as in previous outphasing systems. An RF signal decomposition network directly synthesizes the phaseand amplitude-modulated signals used to drive the branch PAs. With this approach, a modulated RF signal including zero-crossings can be applied to the single RF input port of the outphasing RF amplifier system. The proposed technique is demonstrated at 2.14 GHz in a fourway lossless outphasing amplifier with transmission-line power combiner. The RF decomposition network is implemented using a transmission-line resistance compression network with nonlinear loads designed to provide the necessary amplitude and phase decomposition. The resulting proof-of-concept outphasing power amplifier has a peak CW output power of 93 W, peak drain efficiency of 70%, and performance on par with a previouslydemonstrated outphasing and power combining system requiring four IQ modulators and a digital signal component separator.