A switched reader complementary-loops structure for detecting LF RFID tagged pebbles

This paper presents a reader switched complementary loops structure for pebbles RFID tracking. These so-called "smart pebbles" are tagged with LF RFID glasstags and deployed on beaches, in the context of coastal morpho-dynamics survey. At different periods, the detection of these pebbles over the beach has to be done in the minimum of time. The goal of the project LARGE is to provide a RFID reader antenna structure for reducing the time of the glasstags detection. Technical challenges are that LF glasstags detection is very sensitive to its orientation. As the prototype has to adapt to an unknown orientation and depth of the RFID tags, two key ideas are exploited in this work: (i) the use of complementary loops for reducing the orientation sensitivity and (ii) the switching in loop sizes for adapting to optimal depth of tag detection. A prototype is build and tested with a commercial RFID reader and conclusions of our measurements show that detection performances can be increased with this multiple loops and complementary loops structure.