Enclosure tamper detection and protection

• US 7,468,664 B2
• Filed: 04/20/2007
• Issued: 12/23/2008
• Est. Priority Date: 04/20/2006
• Status: Active Grant

• Current Assignee: NVE Corporation
• Original Assignee: NVE Corporation
• Inventors: Deak, James G., Daughton, James M.
• Primary Examiner(s): Bugg; George A
• Assistant Examiner(s): Tang; Son M
• Application Number:
  US11/788,616
• Publication Number:
  US 20080042834A1
• Time in Patent Office: 613 Days
• Field of Search: 340550-551, 340/561, 340/565, 340/568.1, 340/571, 340/572.6, 340/686.6, 340/545.2
• US Class Current: 340/551
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/1695 Protection circuits or methods

Abstract

A tamper detecting enclosure arrangement for enclosures containing an interior space in which a protected item is positioned having a magnetoresistive sensing memory storage cell positioned in or near the protected item in the enclosure having a two state offset magnetoresistance versus externally applied magnetic field. A magnet is positioned at a selected separation distance from the magnetoresistive sensing memory storage cell to thereby provide a magnetic field about the magnetoresistive sensing memory storage cell if said enclosure has not been opened in such a manner as to result in substantially increasing said separation distance.

Claims

1. A tamper detecting enclosure arrangement for enclosures containing an interior space in which a protected item is positioned to which access is to be denied absent providing a subsequent indication that such an access has occurred, said arrangement comprising:

a magnetoresistive sensing memory storage cell positioned in or near said protected item in said enclosure having a magnetoresistance versus externally applied magnetic field characteristic with two states of differing resistive values which are each entered from that other by applying an external magnetic field having a magnitude change exceeding a magnitude difference between a pair of relatively small transition field value magnitude intervals each having externally applied magnetic field values occurring therein of a common field direction but with those externally applied magnetic field values occurring therein differing in magnitudes from those in that other transition field value magnitude interval, and

a magnet positioned at a selected initial separation distance from said magnetoresistive sensing memory storage cell to thereby provide a magnetic field of initial magnitudes about said magnetoresistive sensing memory storage cell which magnetic field decreases if said enclosure is opened so as to result in substantially increasing a distance separating said magnet and said magnetoresistive sensing memory storage cell, as a resulting opening separation distance, that is larger than said initial separation distance.

2. The arrangement of claim 1 wherein said enclosure has a receptacle with at least part of said interior space therein and a cover which can be positioned so as to render said interior space surrounded by said enclosure.

3. The arrangement of claim 2 wherein said magnet is positioned in said cover.

4. The arrangement of claim 1 wherein said magnetoresistive sensing memory storage cell is formed in a monolithic integrated circuit positioned in said interior space.

5. The arrangement of claim 1 further comprising a portion of a layer of magnetically permeable material positioned adjacent said magnetoresistive sensing memory storage cell.

6. The arrangement of claim 1 further comprising another magnetoresistive sensing memory storage cell positioned in or near said protected item in said enclosure having a magnetoresistance versus externally applied magnetic field characteristic with two states of differing resistive values which are each entered from that other by applying an external magnetic field having a magnitude change exceeding a magnitude difference between a pair of relatively small transition field value magnitude intervals each having externally applied magnetic field values occurring therein of a common field direction but with those externally applied magnetic field values occurring therein differing in magnitudes from those in that other transition field value magnitude interval.

7. The arrangement of claim 6 wherein said magnetic field of initial magnitudes provided by said magnet is about both said magnetoresistive sensing memory storage cells.

8. The arrangement of claim 7 further comprising a conductor coiled adjacent to both said magnetoresistive sensing memory storage cells such that any electrical current established through said conductor tends to place them in opposite resistive value states.

9. The arrangement of claim 1 wherein said magnetoresistive sensing memory storage cell has a length along a selected direction and a width substantially perpendicular thereto that is smaller in extent than said length and together have a shaped end portion extending over a portion of said length in which said width gradually reduces to zero at that end thereof.

10. The arrangement of claim 1 wherein said magnetoresistive sensing memory storage cell has a magnetized body positioned adjacent thereto.

11. The arrangement of claim 1 wherein said enclosure is formed by an electrically insulative solid material body with said interior space limited to what is encapsulated therein which includes said magnetoresistive sensing memory storage cell and said magnet.

12. The arrangement of claim 11 wherein said magnetoresistive sensing memory storage cell is formed in a monolithic integrated circuit positioned in said interior space.

13. The arrangement of claim 11 further comprising a portion of a layer of magnetically permeable material positioned adjacent said magnetoresistive sensing memory storage cell.

14. The arrangement of claim 11 further comprising another magnetoresistive sensing memory storage cell positioned in or near said protected item in said enclosure having a magnetoresistance versus externally applied magnetic field characteristic with two states of differing resistive values which are each entered from that other by applying an external magnetic field having a magnitude change exceeding a magnitude difference between a pair of relatively small transition field value magnitude intervals each having externally applied magnetic field values occurring therein of a common field direction but with those externally applied magnetic field values occurring therein differing in magnitudes from those in that other transition field value magnitude interval.

15. The arrangement of claim 14 wherein said magnetic field of initial magnitudes provided by said magnet is about both said magnetoresistive sensing memory storage cells.

16. The arrangement of claim 15 further comprising a conductor coiled adjacent to both said magnetoresistive sensing memory storage cells such that any electrical current extablished through said conductor tends to place them in opposite resistive value states.

17. The arrangement of claim 11 wherein said magnetoresistive sensing memory storage cell has a length along a selected direction and a width substantially perpendicular thereto that is smaller in extent than said length and together have a shaped end portion extending over a portion of said length in which said width gradually reduces to zero at that end thereof.

18. The arrangement of claim 11 wherein said magnetoresistive sensing memory storage cell has a magnetized body positioned adjacent thereto.