$\mu$WSense: A Self-Sustainable Microwave-Powered Battery-Less Wireless Sensor Node for Temperature and Humidity Monitoring

To realize a green Internet of Things (IoT) sensor network, batteryless wireless sensor nodes (WSNs) are required. This self-sustainability is achieved via energy harvesting from conventional renewable sources, such as solar and wind, which rely on the weather and are highly expensive. Alternatively, the microwave-based wireless power transfer technique is demonstrated previously, however, only for sensing operations without including the IoT. In this letter, a $\mu$Wave-powered WSN ($\mu$Wsense) hardware is demonstrated to realize true batteryless IoT sensing applications. The $\mu$Wsense consists of a rectenna array ($\mu$wave receiver), power management unit, and BLE module. The $\mu$ wave receiver is designed at 5.2 GHz to power $\mu$Wsense at a maximum measured transfer range of 2 m with a maximum real-time sensing interval of 75 s. The minimum harvested power $-16.59$ dBm is sufficient to operate the $\mu$Wsense.