Low-profile, high-permeability antennaless RFID tags for use on metal objects

Radio-frequency identification (RFID) systems are used in asset tracking, but general-purpose tags typically do not perform well on or near metal. Therefore, custom solutions for on metal applications are common. Many solutions for on-metal tags use spacers or electromagnetic band-gap structures resulting in designs that are extremely thick. Our approach was to incorporate materials with permeabilities greater than 1 to create an impedance across a metal surface, diverting current into the tag IC. This type of tag is nearly antennaless as it uses the ground plane or container to excite currents through the IC. Our research has shown that these tags are sensitive to several parameters, such as the size and shape of the plane upon which they are placed, the material used in the antenna, and the type of matching network being used. Tags using magnetic materials in this manner are significantly thinner than those developed using other methods.