A Lightweight, Zero-Power Intermodulation Sensor Based on the Graphene Oscillator

Wireless sensor networks (WSNs) require a massive number of sensor nodes for data collection and storage, for which the power management and area efficiency of battery-powered sensors may be an issue. In this article, we propose and numerically study a fully passive and lightweight intermodulation sensor based on the reconfigurable graphene field-effect transistors (GFETs) oscillator and passive frequency mixer. The output frequency of the self-powered GFET-based oscillator can be sensitive to the surface doping effect caused by charged surface absorbates, reactive gases, contaminations, or aqueous solutions. In the intermodulation sensor, the low-frequency signals generated by GFET oscillator are mixed with the incident radio frequency (RF) waves, forming the retransmitted and the RF intermodulation signals. Since the intermodulation products do not mess up with the reception signal, the unwanted clutters, self-jamming, and interferences can be effectively suppressed. Our results show that the output frequency of the GFET oscillator can sensitively respond to charged molecules, and such information can be encoded in the backscatter intermodulation signal. We believe that our GFET-based intermodulation sensor may be beneficial for a variety of the Internet of Things (IoTs), remote sensing, and environment monitoring applications.