Identification tags using amorphous wire

• US 5,729,201 A
• Filed: 06/29/1995
• Issued: 03/17/1998
• Est. Priority Date: 06/29/1995
• Status: Expired due to Term

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Schrott, Alejandro Gabriel, Jahnes, Christopher, Paunovic, Milan, von Gutfeld, Robert Jacob, Gambino, Richard Joseph
• Primary Examiner(s): MULLEN, THOMAS J
• Application Number:
  US08/496,838
• Time in Patent Office: 992 Days
• Field of Search: 340/572, 340/551, 340/825.34, 235/493
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/06187 with magnetically detectable marking
• CPC Class Codes: G06K 19/067 Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
• CPC Class Codes: G08B 13/2408 using ferromagnetic tags
• CPC Class Codes: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2437 Tag layered structure, processes for making layered tags
• CPC Class Codes: G08B 13/2442 Tag materials and material properties thereof, e.g. magnetic material details

Abstract

An inexpensive multibit magnetic tag is described which uses an array of amorphous wires in conjunction with a magnetic bias field. The tag is interrogated by the use of a ramped field or an ac field or a combination of the two. The magnetic bias is supplied either by coating each wire with a hard magnetic material which is magnetized or by using magnetized hard magnetic wires or foil strips in proximity to the amorphous wires. Each wire switches at a different value of the external interrogation field due to the difference in the magnetic bias field acting on each wire.

Claims

1. A multibit identification tag comprising:

a plurality of magnetic structures, and

one or more bias structures;

each of said magnetic structures being of amorphous metal in the shape of a wire, each of said magnetic structures having the same value of coercive force and wherein each of said plurality of magnetic structures produces a discontinuous change in magnetization at a different value of an externally applied magnetic field.

2. A tag according to claim 1, wherein said bias structures are coatings of a hard magnetic material of different thickness on one or more of said magnetic structures.

3. A tag according to claim 1 wherein said one or more bias structures is in a remanent state.

4. A tag according to claim 1 wherein said one or more bias structures are in the form of a wire.

5. A tag according to claim 1 wherein more than two bias structures are present and said bias structures are of different lengths.