Acoustic wave sensor with EMAT drive

• US 6,933,932 B2
• Filed: 09/17/2002
• Issued: 08/23/2005
• Est. Priority Date: 09/17/2002
• Status: Expired due to Fees

• Current Assignee: Texzec, Inc.
• Original Assignee: Texzec, Inc.
• Inventors: Knowles, Terence J.
• Primary Examiner(s): Mengistu, Amare
• Application Number:
  US10/245,246
• Publication Number:
  US 20040051701A1
• Time in Patent Office: 1,071 Days
• Field of Search: 345173-177, 345/156, 178 1801- 1804, 735/89, 736/43, 736/45
• US Class Current: 345/177
• CPC Class Codes: H03K 17/96 Touch switches specially adapted for electronic time-pieces with no moving parts G04G21/08
• CPC Class Codes: H03K 2217/96011 with propagation, SAW or BAW

Abstract

An acoustic wave sensor includes an electromagnetic acoustic transducer to generate a resonant acoustic wave substantially trapped in an acoustic wave cavity. The acoustic wave cavity is defined by a radially symmetric raised surface. The electromagnetic acoustic transducer includes a spiral primary coil to generate the acoustic wave in the acoustic wave cavity and a concentric spiral pickup coil to pick up an electrical signal representing the acoustic wave in the cavity. A noise canceling coil portion is used to cancel spurious noise induced by the primary coil from the pickup coil to provide an output signal representing the acoustic wave energy in the cavity 12.

Claims

1. An acoustic wave touch sensor comprising:

a body with an acoustic wave cavity formed therein and defined by a raised area, the acoustic wave cavity having a touch surface and at least a portion of the acoustic wave cavity being formed of an electrically conducting material; and

an electromagnetic acoustic transducer positioned adjacent to a surface of the acoustic wave cavity opposite the touch surface, the electromagnetic acoustic transducer having a primary coil generating a resonant acoustic wave in the acoustic wave cavity and a pickup coil providing an electrical output signal, wherein a touch on the touch surface produces a detectable change in the electrical output signal.

2. An acoustic wave touch sensor as recited in claim 1 wherein the entire acoustic wave cavity is formed of an electrically conducting material.

3. An acoustic wave touch sensor as recited in claim 1 wherein the acoustic wave cavity is formed in part of a non-conducting material and in part of an electrically conducting material.

4. An acoustic wave touch sensor as recited in claim 3 wherein the non-conducting material forms at least a portion of the body and the electrically conducting material is mounted on the body and defines the acoustic wave cavity.

5. An acoustic wave touch sensor as recited in claim 4 wherein the touch surface is formed on the electrically conducting material.

6. An acoustic wave touch sensor as recited in claim 4 wherein the touch surface is formed on the non-conducting material.

7. An acoustic wave touch sensor as recited in claim 1 including a noise canceling coil.

8. An acoustic wave touch sensor as recited in claim 7 wherein the primary and pickup coils are positioned under the acoustic wave cavity and the noise canceling coil is not under the acoustic wave cavity.

9. An acoustic wave touch sensor as recited in claim 7 wherein the primary pickup and noise canceling coils are positioned under the acoustic wave cavity.

10. An acoustic wave touch sensor as recited in claim 1 wherein the primary coil has a first portion and a spaced second portion and the pickup coil is disposed in the space between the first and second primary coil portions.

11. An acoustic wave sensor comprising:

a body with a radially symmetric raised surface defining an acoustic wave cavity with at least a portion of the acoustic wave cavity being formed of an electrically conducting material; and

an electromagnetic acoustic transducer positioned adjacent one surface of the acoustic wave cavity, the electromagnetic transducer including a pair of spiral coils, one coil forming a primary coil generating a resonant acoustic wave in the acoustic wave cavity and the other coil forming a pickup coil.

12. An acoustic wave sensor as recited in claim 11 wherein the primary coil and the pickup coil are concentric.

13. An acoustic wave sensor as recited in claim 12 including a noise canceling coil that is concentric with the primary and secondary coils.

14. An acoustic wave sensor as recited in claim 13 wherein the primary coil forms an inner coil, the noise canceling coil forms an outer coil and the pickup coil is disposed between the primary coil and noise canceling coil.

15. An acoustic wave sensor as recited in claim 13 wherein the primary and pickup coils are positioned under the acoustic wave cavity and the noise canceling coil is not under the acoustic wave cavity.

16. An acoustic wave sensor as recited in claim 13 wherein the primary, pickup and noise canceling coils are positioned under the acoustic wave cavity.

17. An acoustic wave sensor as recited in claim 11 wherein the raised surface is circular.

18. An acoustic wave sensor as recited in claim 11 wherein the raised surface is a dome.

19. An acoustic wave sensor as recited in claim 11 wherein the raised surface is spherically symmetrical.

20. An acoustic wave sensor as recited in claim 11 wherein the raised surface is integrally formed with the body.

21. An acoustic wave sensor as recited in claim 11 wherein the raised surface is attached to the body.

22. An acoustic wave sensor as recited in claim 11 wherein the electromagnetic acoustic transducer is adjacent a surface of the acoustic wave cavity opposite of the raised surface.

23. An acoustic wave sensor as recited in claim 11 wherein the electromagnetic acoustic transducer is adjacent the raised surface of the acoustic wave cavity.

24. An acoustic wave sensor as recited in claim 11 wherein the entire acoustic wave cavity is formed of an electrically conducting material.

25. An acoustic wave sensor as recited in claim 11 wherein the acoustic wave cavity is formed in part of a non-conducting material and in part of an electrically conducting material.

26. An acoustic wave sensor comprising:

a body with a domed surface thereon defining an acoustic wave cavity with at least a portion of the acoustic wave cavity being formed of an electrically conducting material; and

an electromagnetic acoustic transducer having a spiral primary coil portion generating a resonant acoustic wave in the acoustic wave cavity, a spiral pickup coil portion and a spiral noise canceling coil portion, the acoustic wave cavity overlying at least the primary coil portion and the pickup coil portion.

27. An acoustic wave sensor as recited in claim 26 wherein the primary coil portion, the pickup coil portion, and the noise canceling coil portion are concentric.

28. An acoustic wave sensor as recited in claim 26 wherein the noise canceling coil position is adjacent one of the other coil portions but the acoustic wave cavity does not overlie the noise canceling coil portion.

29. An acoustic wave sensor as recited in claim 26 wherein the acoustic wave cavity overlies the noise canceling coil portion.

30. An acoustic wave sensor as recited in claim 26 wherein the noise canceling coil portion and the primary coil portions are part of the same coil and the pickup coil portion is disposed between the primary and noise canceling coil portions.

31. An acoustic wave sensor as recited in claim 26 wherein the noise canceling coil portion and the pickup coil portion are part of the same coil and the primary coil portion is disposed between the pickup coil portion and the noise canceling coil portions.

32. An acoustic wave sensor as recited in claim 26 wherein the current in the noise canceling coil is 180°

out of phase with the current in the primary coil.

33. An acoustic wave sensor as recited in claim 26 wherein the domed surface is integrally formed with the body.

34. An acoustic wave sensor as recited in claim 26 wherein the domed surface is attached to the body.

35. An acoustic wave sensor as recited in claim 26 wherein the entire acoustic wave cavity is formed of an electrically conducting material.

36. An acoustic wave sensor as recited in claim 26 wherein the acoustic wave cavity is formed in part of a non-conducting material and in part of an electrically conducting material.

37. An acoustic wave sensor as recited in claim 26 wherein the dome'"'"'s surface is spherically symmetrical.

38. An acoustic wave sensor comprising:

a body with an acoustic wave cavity formed therein and defined by a raised area, at least a portion of the acoustic wave cavity being formed of an electrically conducting material; and

an electromagnetic acoustic transducer having a primary coil portion generating a resonant acoustic wave in the acoustic wave cavity, a pickup coil portion providing an output signal and a noise canceling coil portion adjacent to at least one of the other coil portions to reduce noise in the output signal, the acoustic wave cavity overlying at least the primary coil portion and the pickup coil portion.

39. An acoustic wave sensor comprising:

a body with a radially symmetric raised surface defining an acoustic wave cavity with at least a portion of the acoustic wave cavity being formed of an electrically conducting materials; and

an electromagnetic acoustic transducer positioned adjacent one surface of the acoustic wave cavity, the electromagnetic transducer including a pair of magnets positioned side by side wherein the north pole of one magnet is adjacent the south pole of the other magnet and the boundary between the magnets is aligned with a centerline of the acoustic wave cavity, and the electromagnetic transducer including a pair of concentric spiral coils one coil forming a primary coil generating an acoustic wave in the acoustic wave cavity and another coil forming a pickup coil.

40. An acoustic wave sensor as recited in claim 39 wherein the center of the spiral coil is aligned with the boundary between the magnets and the centerline of the acoustic wave cavity.

41. An acoustic wave sensor as recited in claim 39 including a spiral noise canceling coil portion that is concentric with the primary and pickup coil portions of the electromagnetic acoustic transducer.

42. An acoustic wave sensor as recited in claim 41 wherein the acoustic wave cavity overlies the primary, pickup and noise canceling coil portions.

43. An acoustic wave sensor as recited in claim 41 wherein the acoustic wave cavity overlies the primary and pickup coil portions but does not overlie the noise canceling coil portions.