Multibeam Circular Endfire Array Incorporating Highly Efficient Nona-Band Rectifiers for IoT Energy Harvesting Applications

We introduced a circularly arranged Vivaldi endfire antenna array combined with nona-band rectifiers to enhance the capability of receiving electromagnetic power to supply power for Internet of Things (IoT) devices. The rectifier encompasses frequencies of 0.9, 1.4, 1.8, 2.1, 2.4, 2.6, 3.5, 4.9, and 5.8 GHz, primarily covering telecom and Wi-Fi operating frequencies. Higher efficiency values at a lower input power of -10 dBm were achieved as 73.98%, 54.54%, 63.16%, 27.14%, 59.58%, 56.60%, 46.62%, 21.43, and 20.64% at 0.9, 1.4, 1.8, 2.1, 2.4, 2.6, 3.5, 4.9, and 5.8 GHz, respectively. In addition to the rectifier, we designed a wideband endfire Vivaldi antenna with a 3–8 dB gain over the operating frequencies, with an efficiency exceeding 80%. To further boost the received power, the antenna rectifier was transformed into an eight-element-based circular array, enabling multibeam and full-azimuth power reception coverage. We validated the performance of the rectifier and antenna by fabricating an energy-harvester array. Furthermore, we demonstrate the IoT device operation to illustrate the practical application of our proposed system.