Rectenna Designs for Energy Harvesting IoT Devices: Overview of Current Trends and Future Directions

The number of active Internet of Things (IoT) devices has continued to grow, and today, there are billions of interconnected devices in the world and this large number of devices need energy to be constantly powered, like sensor nodes. This puts a strain on energy requirements for all devices to be powered uninterruptedly. As IoT devices become more and more miniaturized, battery technology has been slower in terms of size and weight, making them inappropriate, or very difficult to replace, for most IoT applications. Radio Frequency energy harvesting has provided a technique for supplementing batteries or eliminating them altogether, especially in low power systems, using a device called Rectenna. In this paper, an overview of the more recent rectenna design trends in the literature are reviewed with respect to their configurations, size, and relevance to contemporary IoT applications. The paper concludes with a brief discussion of possible future directions of rectennas for IoT devices.