Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.3\times $ </tex-math></inline-formula> 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.
Highlights
M ILLIMETER WAVE bands have attracted significant interest for Internet of Things (IoT), Wireless Body Area Networks (WBAN), and sensing applications [1]–[7]
The potential of mmWave wireless power transmission (WPT) for powering wearable IoT devices has been investigated based on a novel broadband antenna
The antenna was analyzed for two WPT applications, a compact power receiver and a large-area array
Summary
M ILLIMETER WAVE bands have attracted significant interest for Internet of Things (IoT), Wireless Body Area Networks (WBAN), and sensing applications [1]–[7]. IoT WBANs have various applications in healthcare monitoring, fitness tracking, defense and wearable sensing [13], [14] Powering such systems using microwave and mmWave rectennas has attracted significant research interest, from UltraHigh Frequency (UHF) to mmWave 5G bands [15]–[17], where wireless power transmission is increasingly seen as a reliable and scalable method for powering the IoT [18]. Several analytical studies have shown that a higher antenna efficiency can be achieved at mmWave bands [10], [11]. This work aims to present a wearable antenna design suitable for mmWave WPT, as well as present an extensive evaluation of its performance as a compact and a large-area power receiver. While several theoretical and practical studies have shown the benefits of mmWave WPT [4], [9], [12], the performance of a mmWave-powered network based on a real antenna, meeting the above criteria, remains unclear. 3) Empirical LoS and N-LoS propagation models, to reflect the higher losses at mmWave bands
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