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

Abstract

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 paper presents a fully-textile rectenna for ultra-low power sub-µW/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-ofart 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 seconds from 10 and 0 dBm, respectively. Wireless testing of the proposed rectenna demonstrates over 50% and 40% PCE below 1 µW/cm 2 in space and on-body, respectively. The rectenna efficiently receives power from mismatched polarization and with a 360 • half-power beamwidth.

Dispenser Printed Flexible Rectenna for Dual-ISM Band High-Efficiency Supercapacitor Charging

“…4 shows the measured charging PCE Average at 433 and 915 MHz, where it can be observed that the rectifier achieves at least 10% average charging PCE. In [14], it was previously shown that for a single-series rectifier the average charging PCE is approximately 66% lower than the peak optimal load PCE. Nevertheless, the peak average PCE of the proposed rectifier is only 58% lower than its optimal load PCE, showing its suitabtility for directly charging a supercapacitor.…”

“…1-b. It was previously shown that inductive matching, combined with a miniaturized layout to maintain a high {Z in }, can achieve a high PCE even on a lossy substrate or conductors [14]. The chosen diode is the Infinion BAT15-04R reverse-pair Schottky diode, the diode was chosen based on its forward voltage (under 300 mV) and its relatively high breakdown voltage of 4 V, enabling high-PCE at a wider input power range than low-breakdown diodes such as the SMS7630.…”

“…where C is the 6.8 mF capacitance, V is the measured DC potential, t is the charging period, and P RF is the input power level [14].…”

Dual-Band Dual-Mode Textile Antenna/Rectenna for Simultaneous Wireless Information and Power Transfer (SWIPT)

“…Textile rectennas are mostly based on off-body antennas [5]- [9], due to their improved isolation. More recently, widebeam omnidirectional "wire-type" antennas such as monopoles were investigated for wearable applications [10]- [12]. While textile-based rectifiers have been used in [5] and [8], their Power Conversion Efficiency (PCE) has been lower than a rigid low-loss rectifier coupled to a textile patch antenna [7].…”

2 × 2 Textile Rectenna Array with Electromagnetically Coupled Microstrip Patch Antennas in the 2.4 GHz WiFi Band

“…Apart from works already included in Table 1, [26,27] present two almost pure textile rectennas working at 0.8 GHz, with peak PCE of up to 63.9% at sub-µW/cm 2 power density levels, providing extremely promising results especially for Wireless Power Transfer (WPT) applications.…”