Electrically Small, Low-Profile, Highly Efficient, Huygens Dipole Rectennas for Wirelessly Powering Internet-of-Things Devices

• Published in: IEEE transactions on antennas and propagation Vol. 67; no. 6; pp. 3670 - 3679
• Main Authors: Lin, Wei, Ziolkowski, Richard W., Huang, Jianquan
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antenna radiation patterns; Batteries; Dipoles; Electric converters; Electrically small rectennas; Energy conversion; Far fields; Huygens radiation pattern; Internet of Things; internet of things (IoT); Rectennas; rectifier circuits; Rectifiers; Substrates; Wireless communication; wireless power transfer (WPT); Wireless power transmission
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2019.2902713

Wireless power transfer (WPT) technologies are a major trend in emerging internet-of-things (IoT) applications. Because they negate the need for heavy, bulky batteries and can power multiple elements simultaneously, WPT systems enable very compact ubiquitous IoT wireless devices. However, the realization of high-performance, ultracompact (electrically small) rectennas, i.e., the rectifying antennas that enable midrange and far-field WPT, is challenging. We present the first electrically small (<inline-formula> <tex-math notation="LaTeX">\textit {ka} < 0.77 </tex-math></inline-formula>) and low-profile (<inline-formula> <tex-math notation="LaTeX">0.04~\lambda _{0} </tex-math></inline-formula>) linearly (LP) and circularly (CP) polarized WPT rectennas at 915 MHz in the IMS band. They are facilitated by the seamless integration of highly efficient rectifiers, i.e., RF signal to dc power conversion circuits, with electrically small Huygens dipole LP and CP antennas. Their optimized prototypes have cardioid, broadside radiation patterns, and effective capture areas larger than their physical size. Experimental results validate that they achieve an 89% peak ac-to-dc conversion efficiency, effectively confirming that they are ideal candidates for many of the emerging IoT applications.