Wireless Power Transmission Powering Miniaturized Low Power IoT devices: A Review

Energy Harvesting (EH) is a mature solution to extend the short lifetime of many wireless sensor nodes and IoT devices. However, miniaturizing EH devices to supply low power and small form factor IoT devices is still challenging and not always effective. In fact, EH from the miniaturized is more challenging due to strict constraints in terms of size, weight, and cost. Among other technologies, wireless power transmission is growing of popularity due to the fact that it can be controlled and it is less unpredictable than environments sources. This paper presents a review of technologies for wireless power transmission that can supply cm-scale low power IoT devices. Additionally, this paper provides in-field evaluation with mm-scale antennas of radio frequency power transmission using a commercial system: Powercast. Experimental results focus on evaluating the power flowing in the battery, which also includes the conversion losses, for different distances and antennas. Infield evaluation shows that it is possible to achieve mW of usable power to one meter and hundreds of mu W at few meters. Those powers are enough for a wide range of low power and miniaturized IoT devices and IoT applications. In conclusion, this paper shows that RF transmission is an effective and alternative way to supply perpetually low power IoT devices.