A Wearable Self-Powered Harmonic-Backscattering SWIPT Tag for Avalanche Rescue Operation

This paper introduces a wearable and selfpowered backscattering sensor tag with multifunctional operations of simultaneous wireless information and power transfer (SWIPT) for avalanche rescue operations. Specifically, the sensor tag is implemented on textile and constructed by a two-port dual-band antenna and a novel 90-degree hybrid coupler (HC) that features distinct signal flows at fundamental (f0) and second-harmonic (2f0) frequencies. By asymmetrically introducing two shorted quarter-wavelength stubs, half of the proposed HC branches feature band-stop responses at 2f0. Consequently, within a single compact structure, the proposed design could harvest the fundamental frequency (f0) to power the communication module via a full-wave rectifying circuit, while the victims’ health and location data is modulated and backscattered to the avalanche rescue transceiver carrying by the second harmonic frequency (2f0) generated from rectifying circuit due to its non-linear behavior. The numerical results show that the self-powering backscatter radio tag operates effectively at both fundamental and second harmonic frequencies. The power conversion efficiency (PCE) of the rectenna achieves nearly 70% and a second harmonic conversion loss (CL) of nearly 20.5 dB at an input RF power of 5 dBm. We envision that the proposed self-powered backscatter sensor tag may be beneficial for applications in personal localizing/sensing systems, and telemedicine healthcare.