Omnidirectional Dual-Polarized Low-Profile Textile Rectenna With Over 50% Efficiency for Sub-μW/cm2 Wearable Power Harvesting

Despite the recent advances in textile antennas, in complete systems such as a rectenna, the efficiency of fully textile solutions has been over 46% lower than hybrid textile/rigid implementations. This article presents a fully textile rectenna for ultralow-power sub- \mu \text{W} /cm 2 applications. A dual-polarized omnidirectional low-profile textile antenna is presented. The rectenna is based on a compact inductively matched rectifier. The textile-based rectifier occupies 0.22 cm 2 and achieves a state-of-the-art power conversion efficiency (PCE) of 41.8% at −20 dBm, at 820 MHz, despite its lossy substrate. A triple-band rectifier is then designed and fabricated to show the scalability of the matching approach. The rectifier is characterized using a new figure of merit "average PCE" over a time period while charging a capacitor. Time-varying S-parameters are used to quantify the impact of the capacitor's charge on the impedance matching. The rectifier directly charges a 1.32 mF capacitor up to 1 V in 0.41 and 4.5 s from 10 and 0 dBm, respectively. Wireless testing of the proposed rectenna demonstrates over 50% and 40% (PCE) below 1~\mu \text{W} /cm 2 in space and on-body, respectively. The rectenna efficiently receives power from mismatched polarization and with a 360° half-power beamwidth.