Underwater UHF RFID Tag for Tracking of Pebbles or Similar Things

RFID tag have gained interest in tracking of pebbles for monitoring the morphodinamics of coasts, bancks and landslides. Generally, Low Frequency (LF) tag are used for that application. In this work we explore the possibility to use UHF tags instead. Appropriate link-budget equations show that this kind of tag can be profitably used in fresh water. We designed a small-sized tag that can be embedded in a pebble and evaluated its ability to be detected from a variable distance when placed in water. The numerical results obtained with a full-wave method are in agreement with those predicted by the link buget equation. The maximum reading distance in fresh water is about 50 cm which is comparable with that of LF tags.