MEMS MICROPHONE

• US 20100142325A1
• Filed: 03/14/2008
• Published: 06/10/2010
• Est. Priority Date: 03/14/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: EPOS Development Limited (Qualcomm, Inc.)
• Inventors: Raif, Ran, Kedem, Noam, Altman, Nathan
• Granted Patent: US 8,861,312 B2
• Time in Patent Office: Days
• US Class Current: 367/118
• CPC Class Codes: G06F 3/0433 in which the acoustic waves are either generated by a movable member and propagated within a surface layer or propagated within a surface layer and captured by a movable member
• CPC Class Codes: G06Q 20/40145 Biometric identity checks
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence

Abstract

A MEMS microphone comprising:

• a) a case with an open front side;
• b) a MEMS membrane mounted on one face of a base, the base being mounted inside the case on a substantially closed side; and
• c) a mesh covering the front side, substantially transparent acoustically to at least some of a range of operating frequencies at which the microphone is sensitive.

Claims

1. A MEMS microphone comprising:

a) a case with a front side open to the exterior, the case comprising an interior volume with a longest dimension being less than half of a highest operating wavelength, and a closed side;

b) a MEMS membrane mounted on one face of a base, the base being mounted inside the case on said closed side; and

c) a mesh covering the open front side, said front side covered by said mesh being substantially transparent acoustically to at least some of a range of operating frequencies at which the microphone is sensitive, the mesh being conductive and grounded, said range comprising ultrasound frequencies and defining said highest operating wavelength.

2. A microphone according to claim 1, also including an amplifier mounted in the case.

3. A microphone according to claim 1, wherein there is a first frequency greater than at least one member of the group comprising 25 kHz, 40 KHz, 70 KHz, and 100 KHz, at which the microphone has a sensitivity of more than −

60 dB, with 0 dB defined as 1 volt per pascal.

7. A microphone according to claim 3, wherein the sensitivity at the first frequency is one member of the group comprising:

greater than −

50 dB, greater than −

40 dB, greater than −

30 dB, no lower than 40 dB below the sensitivity of the microphone at 20 kHz, no lower than 30 dB below the sensitivity of the microphone at 20 kHz, no lower than 30 dB below the sensitivity of the microphone at 20 kHz, is no lower than 20 dB below the sensitivity of the microphone at 20 kHz, no lower than 40 dB below an average of the sensitivity in decibels of the frequencies between 20 kHz and the first frequency, and no lower than 40 dB below a maximum of the sensitivity of the frequencies between 20 kHz and the first frequency.

15. A microphone according to claim 3, wherein the sensitivity varies by one member of the group comprising:

no more than 6 dB over at least 10 kHz, somewhere between 20 kHz and the first frequency, no more than 6 dB over at least 20 kHz, somewhere between 20 kHz and the first frequency, and no more than 6 dB over at least 40 kHz, somewhere between 20 kHz and the first frequency.

18. A microphone according to claim 1, wherein the directional sensitivity of the microphone varies by one member of the group comprising:

no more than 30 dB, for directions in front of the mesh, for the range of operating frequencies for which the sensitivity is within 40 dB of the most sensitive frequency, above 20 kHz, and no more than 20 dB, for directions in front of the mesh, for said range of operating frequencies.

20. A microphone according to claim 1, wherein the substantially solid side is a back side, opposite the front side, and the base is mounted with the MEMS membrane facing the front side.

24. A microphone according to claim 1, wherein the mesh comprises at least one member of the group consisting of:

a fill factor of less than 70%, substantially all the perforations therein having a diameter less than 0.6 mm, and the centers of the perforations therein being arranged substantially in a rhombic grid.

27. A microphone according to claim 1, wherein, for at least one frequency in the range of operating frequencies, defined as the frequencies above 20 kHz which have sensitivity within 40 dB of the most sensitive frequency above 20 kHz, and one direction in front of the mesh, the sensitivity is reduced by less than 10 dB relative to the microphone if the mesh were removed, or wherein for all frequencies in the range of operating frequencies, for at least one direction in front of the mesh, the sensitivity is reduced by less than 10 dB relative to the microphone if the mesh were removed, or wherein, for at least one frequency in the range of operating frequencies, for all directions in front of the mesh, the sensitivity is reduced by less than 10 dB relative to the microphone if the mesh were removed, or wherein for all frequencies in the range of operating frequencies, for all directions in front of the mesh, the sensitivity is reduced by less than 10 dB relative to the microphone if the mesh were removed.

31. A microphone according to claim 1, wherein the front side includes a solid area, for picking and placing, the solid area being at least one member of the group consisting of at least 1 mm square and having an area of filling of the case directly thereunder.

33. A microphone according to claim 1, wherein the membrane is less than 1 mm behind the mesh.

34. A microphone according to claim 1, wherein the case has a plane of substantial symmetry, and the center of the MEMS membrane is within a distance equal to 10% of the largest diameter of the case, of the plane of substantial symmetry, or wherein the case comprises a flat side that the base is mounted on, with the center of the MEMS membrane aligned with the center of the flat side to within 10% of the largest diameter of the case.

36. A microphone according to claim 1, with largest dimension less than 7 mm.

4-6. -6. (canceled)

8-14. -14. (canceled)

16-17. -17. (canceled)

19. (canceled)

21-23. -23. (canceled)

25-26. -26. (canceled)

28-30. -30. (canceled)

32. (canceled)

35. (canceled)

37. An acoustic positioning system comprising:

a) a receiver comprising at least two MEM microphones, that generates a signal in response to ultrasound waves that it receives, at least one microphone being mounted on the receiver so that an outer surface of the microphone is substantially flush, within 5 millimeters, with a surface of the receiver adjacent to and surrounding the microphone;

b) an implement that moves relative to the receiver on a positioning surface on top of which the receiver rests, and comprises at least one ultrasound transmitter that transmits ultrasound waves to the receiver; and

c) a controller that uses the signal to track a position of the implement on the positioning surface.

38. A system according to claim 37, wherein the controller is configured with precision to track the position of the implement to within 4 mm over an area of at least 15 cm by 20 cm, when moving at any speed less than 20 cm/sec.

39. A system according to claim 37, wherein at least one of said MEMS microphones is mounted on the receiver so that a front side of the case is facing above horizontal, when the receiver is resting on the positioning surface, or wherein the front side of the said one microphone is facing more than 45 degrees above horizontal or wherein the front side of the said one microphone is facing less than 45 degrees above horizontal, or wherein a center of the said one microphone is located less than 10 mm above the positioning surface, when the receiver is resting on the positioning surface, or wherein a center of the microphone is located at least 1 mm above the positioning surface, when the receiver is resting on the positioning surface, or wherein said surface of the receiver is substantially parallel to said outer surface of the said one microphone, or wherein a front surface of the receiver, facing the implement anywhere in the area over which the implement is tracked, is oriented at an angle of more than 100 degrees to the positioning surface, when the receiver is resting on the positioning surface, or wherein the front side of the microphone is mounted to the inner surface indirectly, and the board by which it is mounted comprises a flexible printed circuit board.

48. A system according to claim 37, also comprising at least one optical transmitter mounted on the implement, and at least one window in the receiver which receives light from the at least one optical transmitter, to synchronize the receiver with the at least one ultrasound transmitter of the implement.

50. A system according to claim 48, wherein the receiver comprises a front side with a first window of the at least one windows, and a first and second microphone of the at least two microphones arranged laterally on opposite sides of the first window, or wherein at least the first microphone is forward of the first window, thereby blocking a part of a field of view of the first window.

53. A system according to claim 50, wherein the second microphone is also forward of the first window, thereby blocking a part of the field of view of the first window on an opposite side from the part blocked by the first microphone, and the receiver also comprises a third window mounted on a third side of the receiver adjacent to the second microphone, the third window having a field of view that includes at least a part of the field of view of the first window blocked by the second microphone.

60. A system according to claim 53, wherein the front side of the second microphone is directly mounted to the inner surface, or wherein the front side of the second microphone comprises a printed circuit board which extends past the edge of the microphone by at least 1 mm, the back of the extended portion of the printed circuit board thereby providing an attachment surface for handling the microphone during assembly of the microphone to the receiver.

62. A system according to claim 37, further comprising a grill, wherein the grill is at least one member of the group consisting of being symmetric with respect to horizontal reflection, when the receiver is resting on the positioning surface, being symmetric with respect to vertical reflection, when the receiver is resting on the positioning surface, having a fill factor of the grill being less than 50%, wherein spacing between parts of the grill is smaller than half a wavelength of ultrasound for substantially a highest frequency component of the signal used by the controller to track the position of the implement.

66. A system according to claim 37, comprising a conical opening in said receiver.

40-47. -47. (canceled)

49. (canceled)

51-52. -52. (canceled)

54-59. -59. (canceled)

61. (canceled)

63-65. -65. (canceled)

67. A MEMS microphone comprising:

a) a case with an open front side, any solid area being filled in underneath;

b) a MEMS membrane mounted on one face of a base, the base being mounted inside the case on a substantially closed side; and

c) a mesh covering the front side, substantially transparent acoustically to at least some of a range of operating frequencies at which the microphone is sensitive.

69. An acoustic positioning system comprising:

a) a receiver comprising at least two MEM microphones, that generates a signal in response to ultrasound waves that it receives, wherein a surface of the receiver, adjacent to at least one microphone, is curved convexly, and substantially no surface of the receiver, other than a bottom surface resting on the positioning surface, is oriented in a direction below horizontal;

b) an implement that moves relative to the receiver on a positioning surface on top of which the receiver rests, and comprises at least one ultrasound transmitter that transmits ultrasound waves to the receiver; and

c) a controller that uses the signal to track a position of the implement on the positioning surface.

70. An acoustic positioning system comprising:

a) a receiver comprising at least two MEMS microphones, that generates a signal in response to ultrasound waves that it receives, wherein a substantially solid front side of at least one of the microphones, with an acoustic port, is mounted to an inner surface of a front side of the receiver, with the acoustic port behind an opening in the receiver that is less than 5 mm long, mounted directly to the inner surface, or mounted indirectly to the inner surface behind the opening in the receiver by a board with an opening intermediate in size between the opening in the receiver and the acoustic port, said microphone having a MEMS membrane on a base mounted over the acoustic port on an inner surface of the front side, facing backwards;

b) an implement that moves relative to the receiver on a positioning surface on top of which the receiver rests, and comprises at least one ultrasound transmitter that transmits ultrasound waves to the receiver; and

c) a controller that uses the signal to track a position of the implement on the positioning surface.