A Circularly Polarized Wireless Power Transfer System for Internet-of-Things (IoT) Applications

A circularly polarized (CP) wireless power transfer (WPT) system is demonstrated. It consists of a high directivity, omnidirectional CP (OCP) antenna array and multiple electrically small Huygens CP (HCP) rectennas. The OCP array emits highly directional CP fields over the entire azimuthal plane. It acts as the wireless power source for charging or powering up surrounding IoT sensors. The OCP array is realized by cascading multiple vertical bars and helical loops to form a set of properly phased, collinear array of electric and magnetic dipoles. Wirelessly powered (WP) sensors are facilitated by combining sensors with HCP rectennas, the latter being a seamless integration of an electrically small HCP antenna with highly efficient rectifier circuits. Both systems were tested and achieved their predicted performance characteristics. These WP sensor systems are ideal candidates for wireless internet-of-things (IoT) applications, for example, in the food and agriculture industries, which are amongst the largest enterprises in Australia.