A Performance Analysis Framework for Passive UHF RFID for Environmental Applications

Radio frequency identification (RFID) technology has been widely used in various industries due to its object identification and monitoring capability. In recent years, low-frequency (LF) RFID has been increasingly used in hydraulic studies for sediment transport studies and the detection of underground utilities. Nevertheless, prior studies have indicated that the use of LF RFID technology is limited due to its short detection range and high sensitivity of orientation relative to the antenna place. Ultra-high frequency (UHF) RFID (865-928 MHz) technology has much longer reading ranges compared to the LF RFID. However, up to date, the application of UHF RFID technology in aquatic environments is still rare because of its high sensitivity to water. This study aims to investigate the reading range behaviors of passive UHF RFID tags for surface applications in aquatic environments. This research used circular and linear polarization antennae, which have a gain of 8 dBic, 9 dBic, and 12.5 dBi, respectively, to examine six pre-selected UHF RFID tags behaviors. The results of this study showed that a decrease in the performance of maximum reading distances when the tags are placed in a vertical orientation at the center of the antenna compared with the horizontal orientation. The maximum reading ranges varied between 1 to 35% when using the 8 dBic antenna, between 0% to 48% with the 9 dBic antenna, and between 14 to 82% with the 12.5 dBi antenna. Based on key findings and observations from this study, we demonstrated design requirements of tags to overcome sensitivity limitations to design for future surface-water velocity monitoring applications in the natural open water and built water transport environments.