Sub- {\mu} W Battery-Less and Oscillator-Less Wi-Fi Backscattering Transmitter Reusing RF Signal for Harvesting, Communications, and Motion Detection

TL;DR

This paper introduces a battery-less, oscillator-less Wi-Fi backscattering transmitter that reuses RF signals for energy harvesting, communication, and motion detection, achieving ultra-low power operation and device miniaturization.

Contribution

It demonstrates a novel sub-microW Wi-Fi backscatter system that eliminates the need for a local oscillator and off-chip sensors, enabling ultra-low power, battery-less, and highly miniaturized devices.

Findings

Achieved sub-uW power consumption for Wi-Fi backscatter.

Enabled RF harvesting, communication, and motion sensing using the same incident wave.

Demonstrated sensitivity down to -19 dBm with no off-chip components.

Abstract

In this paper, a sub-uW power 802.11b backscattering transmitter is presented to enable reuse of the same incident wave for three purposes: RF harvesting, backscattering communications and position/motion sensing. The removal of the battery and any off-chip motion sensor (e.g., MEMS) enables unprecedented level of miniaturization and ubiquity, unrestricted device lifespan, low fabrication and maintenance cost. The uW power wall for WiFi transmitters is broken for the first time via local oscillator elimination, as achieved by extracting its frequency through second-order intermodulation of a twotone incident wave. The two-tone scheme also enables a cumulative harvesting/transmission/sensing sensitivity down to Pmin -19 dBm. Position/motion sensing is enabled by using the harvested voltage as a proxy for the Received Signal Strength (RSS), allowing to sense the chip location with respect to the tone generator(s) shared across tags in indoor neighborhoods.