Coded labels with amorphous magnetoelastic resonators

Summary form only given. Strips or wires made from magnetoelastic amorphous alloys are widely used as magnetoelastic resonators in security labels for electronic article surveillance systems. A new identification system employs coded labels based on this technology. The labels contain two to eight magnetoelastic resonators having resonance frequencies between 20 kHz and 85 kHz being arranged in up to 18 possible orientations. The resonance frequencies can be shifted by a static bias magnetic field. Thus, by generating a rotating bias magnetic field vector by means of a coil system, the lengths and the orientation angles of the resonators can be detected and the label can be decoded. A number of up to 13 million differently coded labels can be decoded by such a system. Starting from the coding principle of the labels, an investigation of novel and known iron-based resonator materials are presented and their usability for coded labels are discussed. The influence of resonator geometry, mass loading and resonator bearing was investigated. Furthermore, we present a new flexible bearing technique that allows for low damping bearing of the resonators. Finally, sample results illustrating the performance of prototype labels in an actual decoding system are discussed.