Simultaneous Detection of Multiple Surface Acoustic Wave Sensor Tags for Water Quality Monitoring Utilizing Cellular Code-Reuse Approach

A water quality monitoring application often requires the deployment of Internet-of-Things (IoT) sensors over a wide water body with communication links among them to transmit, receive the data, and then uplink it to the cloud for further analytics. Deployment of this kind requires battery-assisted IoT sensors which require monitoring the battery level and replacement when necessary. It is thus desirable to have battery-free sensor tags and a suitable communication infrastructure to obtain data. In this article, a system that facilitates obtaining sensed data, like pH, through passive sensor tags based on surface acoustic wave (SAW) technology and a cellular code-reuse scheme-based reader infrastructure is proposed. The reader in each cell is able to read multiple sensor tags simultaneously, which itself has been a challenge. The SAW sensor tags are appropriately proposed to be designed to be orthogonal to allow simultaneous detection and the cell range of reader-SAW sensor-tags communication is sought to be further enhanced through a resonant loading of interdigital transducer (IDT)-based reflectors.