Analysis and design of a limit-cycle envelope amplifier for wireless transmitters

Manuel J. Duarte


Limit-cycle or self-oscillating power amplifiers (SOPAs) are seen as a compact option to achieve efficient yet linear amplification of either complete RF signals or only their base-band envelopes. This paper summarizes the work carried out in the Master Thesis of the author, which consisted on the analysis and design of a limit-cycle amplifier, taking into account the propagation delay of the relay. For that, the theory of its working principle is discussed, and a prototype is built. During the work, a method to increase the selfoscillation frequency for a fixed propagation delay and loop filter was proposed, which consists on replacing the relay with one that exhibits a novel kind of hysteresis. To validate the concept, simulations are carried out to compare the behavior of existing types of SOPA with the proposed one.


limit-cycle amplifier; negative hysteresis; power amplifiers; relay control system

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