Millimeter-Wave Power Transmission for Compact and Large-Area Wearable IoT Devices Based on a Higher Order Mode Wearable Antenna

• Published in: IEEE internet of things journal 2022-04, Vol.9 (7), p.5229-5239
• Main Authors: Wagih, Mahmoud, Hilton, Geoffrey S., Weddell, Alex S., Beeby, Steve
• Format: Article
• Language: English
• Subjects: Antenna arrays; Antenna measurements; Antennas; Bandwidth; Broadband; Broadband antennas; Empirical analysis; Internet of Things; Microstrip antennas; Millimeter waves; millimeter-wave (mmWave) antenna; permittivity measurements; radio-frequency (RF) energy harvesting (EH); Receivers; Receivers & amplifiers; Receiving antennas; rectenna; Rectennas; Ultrahigh frequencies; Wave power; Wearable technology; wireless power transfer; Wireless power transmission
• ISSN: 2327-4662; 2327-4662
• DOI: 10.1109/JIOT.2021.3107594

Owing to the shorter wavelength in the millimeter-wave (mmWave) spectrum, miniaturized antennas can receive power with a higher efficiency than UHF bands, promising sustainable mmWave-powered Internet of Things (IoT) devices. Nevertheless, the performance of a mmWave power receiver has not been compared, numerically or experimentally, to its sub6-GHz counterpart. In this article, the performance of mmWave-powered receivers is evaluated based on a novel wearable textile-based higher order mode microstrip antenna, showing the benefits of wireless power transmission (WPT). First, a broadband antenna is proposed maintaining a stable wearable measured bandwidth from 24.9 to 31.1 GHz, over threefold improvement compared to a conventional patch. The proposed antenna has a measured 8.2 dBi co-polarized gain with the highest thickness-normalized efficiency of a wearable antenna. When evaluated for compact power receivers, the measured path gain shows that WPT at 26 GHz outperforms 2.4 GHz by 11 dB. A rectenna array based on the proposed antenna is then evaluated analytically showing the potential for up to 6.3\times higher power reception compared to a UHF patch, based on the proposed antenna's gain and an empirical path-loss model. Both use cases demonstrate that mmWave-powered rectennas are suitable for area-constrained and large-area wearable IoT applications.