MULTIPLE FREQUENCY TAG

摘要

A multiple frequency tag (118, 218) in one embodiment comprises a generally fiat dielectric substrate (220) having first and second generally opposite principal surfaces. A first resonant circuit including a first inductor coil (222) is located on the first surface of the substrate, the first resonant circuit having a first predetermined resonant frequency. A second resonant circuit including a second inductor coil (232) is located on the second surface of the substrate. The second resonant circuit has a second predetermined resonant frequency which preferably is different from the first predetermined resonant frequenc y. The first inductor coil is positioned on the substrate to partially overlie the second inductor coil in a manner which minimizes the magnetic coupling between the first and second coils. The tag may be employed in an electronic article security system (10) for protecting articl es or may be employed in any other type of system for detecting the presence of a tag.