Millimeter-Wave Textile-Based Monopole Antenna for Wearable Wireless Power Transmission

Abstract

With a wide bandwidth and a high potential for antenna miniaturization, the millimeter-wave (mmWave) bands have attracted interest for a range of wearable applications. In this paper, a textile-based end-fire monopole is proposed for wireless power transmission (WPT) applications. The proposed Yagi-inspired antenna bandwidth covers the 24 GHz license-free band. The antenna achieves 73% total efficiency, a 2.5 dB improvement over a microstrip patch on the same textile substrate. The antenna has a peak gain over 4 dBi with a wide 80° half-power beamwidth both in space and on a layered human tissue model. The antenna is experimentally characterized for line-of-sight WPT showing a 7 dB forward transmission improvement compared to 2.45 GHz WPT, for 55 cm separation, between two symmetric antennas with sub-cm ² area. Given the antenna's 0.4 cm ² area, it is shown that mmWaves enable high-efficiency WPT to miniaturized antennas in future 5G networks.