Self-powered piezoelectric wireless micro-sensors by absorbing electromagnetic energy

This paper presents a new scheme for a self-powered micro-sensor by absorbing electromagnetic energy. A unidirectional transducer group and a resonant acoustic cavity are created inside the transducer while keeping the unidirectionality required for low loss. As a result, the electromagnetic energy collected from the antenna can be converted into acoustic energy and stored in the resonant cavity. The energy output in another path is controlled by a specific circuit. Therefore the electromagnetic energy can be gathered and accumulated ceaselessly, and the collecting energy can be released and produce a high power in a very short term. Measurement on a 70 MHz device demonstrates that the resonant frequency in the resonator is related to the measured parameter and the sensor can be deployed in long distance detection.