High Efficiency, High Power, Variable Output of Multiple Power Amplifiers

Researchers at Stanford have developed a method to tune power amplifier circuits to directly connect their output power (and adjust the combined output power) without any additional power combiner network. This method allows any number of amplifiers to be combined while isolating their influence on each other. It eliminates efficiency losses; decreases system size, weight, and cost associated with a combiner network; and outperforms state of the art. (See Table 1 for comparison.) In addition, Stanford researchers can modulate the combined power output via phase control and power combining using a system with multiple power amplifiers connected in parallel. Output power is adjusted by selecting a number of amplifiers, and fine-tuned by running some power amplifiers 'backward.' This method significantly outperforms state of the art both at full load and light load (Table 2), making it ideal for radiofrequency (RF) plasma generating systems, and footprint /weight limited applications such as RF communication for mobile phones and micro-satellite propulsion.

Stage of Development – Proof of Concept
The Stanford University Power Electronics Research Lab demonstrated three power amplifier systems, each with six sub-circuits, with combined output of 1500W @40.68 MHz; 1500W@13.56 MHz; and 2200 W@40.68 MHz. The SUPER lab power amplifiers significantly outperformed state of the art. Research is ongoing.