MULTI-THREAD RE-ENTRANT MARKER WITH TRANSVERSE-ANISOTROPY FLUX CONCENTRATORS

摘要

A marker (20) for a harmonic electronic article surveillance system includes three wires (21) of magnetic material arranged in parallel. The material has a magnetic hysteresis loop with a large Barkhausen discontinuity such that, upon exposure of the marker (20) to an external magnetic field whose field strength in the direction opposing the instantaneous magnetic polarization of the marker exceeds a predetermined threshold value, there results a regenerative reversal of the magnetic polarization in the material. The three wires (21) are coupled at opposite ends thereof by flux concentrating elements (22, 23) formed of a highly permeable material so that all three wires exhibit the regenerative reversal simultaneously on exposure to the above-described magnetic field. The flux concentrators have magnetic anisotropies oriented transversely relative to the length of the wires to aid in coupling the wires for simultaneous switching.