Magnetic-Field Coupling Characteristics of Ferrite-Coil Antennas for Low-Frequency RFID Applications

Low-frequency technology has been widely used for detecting objects placed underground. Low-frequency radio-frequency identification (RFID) systems provide the advantage of better propagation in lossy materials such as rocks and soil. In this paper, we assume that buried objects will be tagged with low frequency RFID passive transponders and that a reader with the large single-loop antenna will be used to detect the objects. We propose new orientation-insensitive transponder’s antenna. Simulated and measured results obtained from fabricated antennas based on the new design show some advantage over the traditional design. The new antenna offers a more uniform magnetic field pattern.