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A Battery-Free Smart Sensor Powered with RF Energy

The development of Internet of Things (IoT) infrastructure and applications is stimulating advanced and innovative ideas and solutions, some of which are pushing the limits of state-of-the-art technology. The increasing demand for Wireless Sensor Network (WSN) that must be capable of collecting and sharing data wirelessly while often positioned in places hard to reach and service, motivates engineers to look for innovative energy harvesting and wireless power transfer solutions to implement battery-free sensor nodes. Due to the pervasiveness of RF (Radio Frequency) energy, RF harvesting that can reach out-of-sight places could be a key technology to wirelessly power IoT sensor devices, which in order to be ubiquitous, need to be wireless, maintenance-free, battery-free and low cost enough to be used almost anywhere. In this article the implementation of an RF power transfer system for battery-free wireless sensor nodes will be shown. The system comprises an RF power transmitter which delivers a power of 0.5 W at 900 MHz and an RF energy harvesting which is used as an RF power receiver to power a battery-free sensor node. Experimental results will show how the system can feed a 10 mA load for a 50 ms acquisition time with the transmitted power delivered from several distances.