Anti-collision interrogation pulse focusing system for use with multiple surface acoustic wave identification tags and method of operation thereof

• US 20030179077A1
• Filed: 03/21/2002
• Published: 09/25/2003
• Est. Priority Date: 03/21/2002
• Status: Active Grant

• Current Assignee: RF Saw Components Incorporated
• Original Assignee: RF Saw Components Incorporated
• Inventors: Hartmann, Clinton S., Claiborne, Lewis T.
• Granted Patent: US 7,084,768 B2
• Time in Patent Office: Days
• US Class Current: 340/10.2
• CPC Class Codes: G01S 13/755 using delay lines, e.g. acoustic delay lines
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10029 the collision being resolved in the time domain, e.g. using binary tree search or RFID responses allocated to a random time slot
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions

Abstract

The present invention provides a system for avoiding code collisions from multiple SAW identification tags and a method of operating such system. In one embodiment the invention provides for (1) focusing an interrogation pulse to within a defined space; and (2) discriminating between coded responses returned from tags located within such defined space.

Claims

1. A system for avoiding code collisions from multiple SAW identification tags, comprising:

focusing an interrogation pulse to within a defined space; and

discriminating between coded responses returned from tags located within said defined space.

2. The system as described in claim 1 wherein beam steering is used to focus said interrogation pulse within said defined space.

3. The system as described in claim 1 wherein an antenna is used to focus said interrogation pulse within said defined space.

4. The system as described in claim 3 wherein said antenna is a parallel conductor pair.

5. The system as described in claim 3 wherein said antenna is a helical antenna.

6. The system as described in claim 3 wherein said antenna is a dielectric waveguide antenna.

7. The system as described in claim 3 further comprising a reflector coupled to said antenna.

8. The system as described in claim 7 wherein said reflector is an elliptical trough.

9. The system as described in claim 7 wherein said reflector is selected from the group consisting of:

a circular reflector;

a curved reflector;

a parabolic reflector;

a re-entrant cavity; and

an elliptical reflector.

10. The system as described in claim 1 wherein said interrogation pulse is focused within said defined space by a waveguide.

11. The system as described in claim 10 wherein said waveguide projects a circular polarized beam.

12. The system as described in claim 10 wherein said waveguide has a first feed of about one-quarter wave length positioned at about a 90°

position relative to a second feed of about one-quarter wave length.

13. The system as described in claim 10 wherein a reflector is coupled to said waveguide.

14. The system as described in claim 13 wherein said reflector is selected from the group consisting of:

a circular reflector;

a curved reflector;

a parabolic reflector;

a re-entrant cavity; and

an elliptical reflector.

15. A method for operating a system for avoiding code collisions from multiple SAW identification tags, comprising:

focusing an interrogation pulse to within a defined space; and

discriminating between coded responses returned from tags located within said defined space.

16. The method as described in claim 15 wherein said focusing uses beam steering.

17. The method as described in claim 15 wherein said focusing uses an antenna.

18. The method as described in claim 17 wherein said antenna is a parallel conductor pair.

19. The method as described in claim 17 wherein said antenna is a helical antenna.

20. The method as described in claim 17 wherein said antenna is a dielectric antenna.

21. The method as described in claim 17 further comprising a reflector coupled to said antenna.

22. The method as described in claim 21 wherein said reflector is an elliptical trough.

23. The method as described in claim 21 wherein said reflector is selected from the group consisting of:

a circular reflector;

a curved reflector;

a parabolic reflector;

a re-entrant cavity; and

an elliptical reflector.

24. The method as described in claim 15 wherein said focusing uses a waveguide.

25. The method as described in claim 24 wherein said waveguide projects a circular polarized beam.

26. The method as described in claim 24 wherein said waveguide h as a first feed of about one-quarter wave length positioned at about a 90°

position relative to a second feed of about one-quarter wave length.

27. The method as described in claim 24 wherein a reflector is coupled to said waveguide.

28. The method as described in claim 27 wherein said reflector is selected from the group consisting of:

a circular reflector;

a curved reflector;

a parabolic reflector;

a re-entrant cavity; and

an elliptical reflector.

29. A system for avoiding code collisions from multiple SAW identification tags, comprising:

directing an interrogation pulse having a circular polarity toward said tags, said interrogation pulse generating a corresponding SAW in each of said tags that travels a preselected direction; and

receiving coded responses from only ones of said tags responding to said interrogation pulse.

30. The system as described in claim 29 wherein said circular polarity is clockwise.

31. The system as described in claim 29 wherein said circular polarity is counterclockwise.

32. The system as described in claim 29 further comprising using a hollow cylindrical waveguide to direct said interrogation pulse.

33. The system as described in claim 32 wherein said waveguide is metallic.

34. The system as described in claim 29 further comprising using a solid cylindrical waveguide to direct said interrogation pulse.

35. The system as described in claim 34 wherein said waveguide is a dielectric.

36. The system as described in claim 34 wherein said waveguide has a metallic outer surface.

37. The system as described in claim 29 further comprising a reflector to direct said interrogation pulse.

38. The system as described in claim 37 wherein said reflector is selected from the group consisting of:

a circular reflector;

a curved reflector;

a parabolic reflector;

a re-entrant cavity; and

an elliptical reflector.

39. The system as described in claim 29 wherein said tags can be turned off.

40. The system as described in claim 39 wherein a transducer is used to turn off said tags.

41. The system as described in claim 39 wherein an absorbing reflector is used to turn off said tags.