Multifunctional Sensing Platform Based on Single Antenna for Noncontact Human–Machine Interaction and Environment Sensing

Antenna sensors are promising microwave sensor variants that combine the benefits of easy fabrication, nondestructive detection, and robust performance with integrated communication capabilities, making them ideal for Internet-of-Things (IoT) sensor nodes that require both sensing and communication. However, existing antenna sensors lack multifunctionality and require additional circuitry to maintain the fixed communication band, which increases the complexity. Considering these challenges, in this work, we propose a multifunctional antenna sensor capable of hand gesture recognition, volatile organic compound (VOC) gas identification, permittivity characterization, and fixed band communication. By replacing the large sensor array in the conventional gesture radar sensor and VOC electronic nose (e-nose) with a single piece of uniplanar antenna sensor, we integrate all the above functions on a $33\times 33$ mm substrate, reducing system complexity and costs significantly. By extracting rich features over ultrawideband and using efficient machine learning (ML) algorithms, ten gestures and six VOC gases (including isomers) are successfully discriminated with 94.1% and 100% measurement accuracy, respectively. In addition, different types of liquids and substrate blocks are also successfully characterized without affecting the communication band. Our proposed antenna sensor promises advancement in the next generation of IoT sensor nodes.