LF RFID chequered loop antenna for pebbles on the beach detection

This paper focus on low frequency (125 kHz) RFID by magnetic coupling, more precisely using glasstag type of tags in the context of pebble detection on the beach. The challenge is to detect over a wide area very small size tags which are highly sensitive to the orientation of the magnetic field. To improve the detection ability of the reader loop antenna, the paper proposes to exploit the principle of complementary loops. Theoretical simulations with MATLAB show the potential increase by means of mutual inductance value along a displacement of the tag. A prototype of a chequered loop structure is presented and tested with a classical low power RFID reader to demonstrate the improvement without increasing the current in LF reader loops. The detection performances reach 12,8% for a 900 cm2 surface of a prototype reader loop, whatever the orientation of the glasstag.