High-efficiency microwave circuits

Several projects (since 1995) deal with high-efficiency microwave circuits using switched-mode operation. This means that the circuit around a transistor is designed in such a way that the current and voltage across the device terminals are never non-zero simultaneously, resulting in theoretically zero VI product, or 100% efficiency. We have used this method to successfully design power amplifiers from 1 to 10GHz with over 60% efficiencies, frequency doublers with conversion gain and 40% efficiency from 10 to 20GHz, oscillators and active oscillating antennas with over 50% conversion efficiency, and we are expanding to rectification devices as well. The theses of Tom Mader, Milica Markovic, Eric Bryerton and Manoja Weiss have all contributed to this area. We have also collaborated with Profs. John Whitaker and Linda Katehi at the University of Michigan on using their optical sampler to measure voltage waveforms at different points inside a switched-mode circuit to verify our designs.

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