Intelligent resonance tracking of a microwave plasmonic resonator for compact wireless sensors

Plasmonic sensing has been in the spotlight for decades, the concept and applications of which have been generalized to spoof surface plasmons (SSPs) in the microwave band. Here, we report a compact and wireless sensor within a printed circuit board size of 18 mm * 12 mm, tracking the resonance frequency shift of a microwave plasmonic resonator via a software-defined scheme. The microwave plasmonic resonator yields a deep-subwavelength size, enhanced sensitivity, and a good electromagnetic compatibility performance. The software-defined resonance tracking scheme minimalizes the hardware circuit and the consumed spectrum resources, and makes the detection intelligently adaptive to the target resonance, with a signal-to-noise ratio of 69 dB and a data rate of 2272 measuring points per second. The sensor has been validated via acetone vapor concentration sensing, while its applications can be widely extended by replacing the transducer materials. This approach provides compact, sensitive, accurate and intelligent solutions for resonant sensors in the Internet of things (IoT).