Broadband Millimeter-Wave Textile-Based Flexible Rectenna for Wearable Energy Harvesting

Abstract

Millimeter-wave (mmWave) bands, a key part of future 5G networks, represent a potential channel for RF energy harvesting, where the high-gain antenna arrays offer improved end-to-end efficiency compared with sub-6-GHz networks. This article presents a broadband mmWave rectenna, the first rectenna realized on a flexible textile substrate for wearable applications. The proposed novel antenna's bandwidth extends from 23 to 40 GHz, with a minimum radiation efficiency of 67% up to 30 GHz, over 3-dB improvement compared with a standard patch. A stable gain of more than 8 dB is achieved based on a textile reflector plane. The antenna is directly connected to a textile-based microstrip voltage doubler rectifier utilizing commercial Schottky diodes. The rectifier is matched to the antenna using a tapered line feed for high-impedance matching, achieving broadband high voltage sensitivity. The rectifier has a peak RF-dc efficiency of 12% and a 9.5-dBm 1-V sensitivity from 23 to 24.25 GHz. The integrated rectenna is demonstrated with more than 1.3-V dc output from 12 dBm of mmWave wireless power across a 28% fractional bandwidth from 20 to 26.5 GHz, a 15% half-power fractional bandwidth, and a peak output of 6.5 V from 20 dBm at 24 GHz.