EcoSense: An Autonomous Polarization-Insensitive Wireless-Powered Battery-Free IoT Beacon for Live Environmental Sensing

The battery-free wireless sensor beacons (WSB) are essential for realizing a green and self-sustainable operation for power-constrained Internet of Things (IoT) applications. With increasing communication activities and availability, the radio-frequency (RF) energy harvesting using a rectenna has become a reliable solution to energize the WSB wirelessly. Prior literary works indicate that the energy harvesting of a rectenna depends on the wave polarization between the rectenna and the transmitter to effectively capture the maximum incoming waves from any orientation, allowing the deployment of IoT nodes without requiring specific alignment. However, simultaneous effective energy harvesting and data transfer over a long distance at ultra-low-power is still an issue. Therefore, a novel RF-powered battery-free IoT beacon with a polarizationinsensitive (PoI) feature is developed and demonstrated for ultra-low- power IoT sensing applications. This WSB is completely integrated and miniaturized with implementing both wireless power and data transfer, which is developed on a multilayer PCB (printed circuit board). The WSB consists of a rectenna array operating at 5.2 GHz for wireless power, an integrated circuitry of a power management unit (PMU), and a Bluetooth low energy (BLE) module for data transfer. The WSB operates at a minimum received microwave power of −15.18 dBm. The results demonstrate the system to be wirelessly energized at a transfer range of 11 m away from the transmitter emitting 47.22 dBm power and realizing battery-free operation for IoT sensors. Thus, this design is suitable for orientation-independent WSB operations in IoT applications such as environmental monitoring and smart agriculture applications in remote areas.