Ultrasonic MEMS transmitter

• US 9,457,379 B2
• Filed: 03/11/2013
• Issued: 10/04/2016
• Est. Priority Date: 12/10/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Amm, David, Yang, Henry, Last, Matthew Emanuel
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US13/794,417
• Publication Number:
  US 20140157904A1
• Time in Patent Office: 1,303 Days
• Field of Search: 736/32, 736/27, 736/42, 367 92- 94, 367/103, 367/87
• US Class Current: 1/1
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: G01B 17/00 Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
• CPC Class Codes: G01S 15/74 Systems using reradiation of acoustic waves, e.g. IFF, i.e. identification of friend or foe
• CPC Class Codes: G01S 7/521 Constructional features
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005

Abstract

Ultrasonic transmitters that can be used for ranging in mobile devices are disclosed. In some examples, an ultrasonic transmitter device can be configured to transmit ultrasonic signals in multiple frequency bands. The transmitter can include multiple sets of ultrasonic transmitters, each capable of transmitting in a different frequency band. In other examples, frequency-adjustable ultrasonic transmitters can be used. The transmitters can be configured to change one or more of a length, mass, or tension of a membrane to change a resonant frequency of the membrane. In some examples, the transmitter can include a non-uniformly shaped membrane capable of vibrating at more than one resonant frequency. The ultrasonic transmitters can be included within a housing configured to control the flow of air within and out of the housing. The transmitter membrane can further be formed on a patterned substrate configured to increase the sound pressure levels produced by the transmitter.

Claims

1. A transmitter comprising:

a drum;

a membrane coupled to the drum;

a first electrode coupled to the drum;

a second electrode coupled to the membrane; and

a plurality of posts disposed within the drum, wherein the plurality of posts have non-uniform heights such that;

while the membrane is in a first configuration, a first post of the plurality of posts causes the membrane to have a first length; and

while the membrane is in a second configuration, a second post of the plurality of posts causes the membrane to have a second length, different from the first length;

wherein the membrane is configured to transmit an ultrasonic signal at a first frequency, corresponding to the first length, when a signal having a first DC voltage component is applied to the first electrode, and wherein the membrane is configured to transmit an ultrasonic signal at a second frequency, corresponding to the second length, when a signal having a second DC voltage component is applied to the first electrode.

2. The transmitter of claim 1, wherein a height of the first post of the plurality of posts is less than a height of the second post of the plurality of posts, and wherein the first post is positioned closer to a center of the membrane than the second post.

3. The transmitter of claim 2, wherein the membrane is configured to contact the first post when the signal having the first DC voltage component is applied to the first electrode, and wherein the membrane is configured to contact the second post when the signal having the second DC voltage component is applied to the first electrode.

4. The transmitter of claim 1, wherein the membrane is circular in shape, and wherein each of the plurality of posts form concentric circles within the drum.

5. The transmitter of claim 1, wherein the transmitter is a microelectromechanical system (MEMS) transmitter.

6. The transmitter of claim 1 wherein the transmitter is enclosed within a housing, and wherein the housing comprises one or more dividers to control flow of air out of the housing.

7. A transmitter comprising:

a drum;

a first membrane coupled to the drum;

a second membrane coupled to the drum;

a first electrode coupled to the drum;

a second electrode coupled to the first membrane;

a third electrode coupled to the first membrane opposite the second electrode; and

a fourth electrode coupled to the second membrane, wherein the first membrane is separate from the second membrane when a signal having a first DC voltage component is applied to the third electrode, and wherein the first membrane and second membrane are coupled together when a signal having a second DC voltage component is applied to the third electrode.

8. The transmitter of claim 7, wherein the transmitter is configured to transmit an ultrasonic signal having a first frequency when the signal having the first DC voltage component is applied to the third electrode, and wherein the transmitter is configured to transmit an ultrasonic signal having a second frequency when the signal having the second DC voltage component is applied to the third electrode.

9. A transmitter comprising:

a drum;

a membrane coupled to the drum, the membrane having a shape including a length and a width, wherein the width is shorter than the length;

a first electrode coupled to the drum; and

a second electrode coupled to the membrane, wherein the membrane is configured to transmit an ultrasonic signal having a first frequency, corresponding to the width, in response to applying a first signal to the first electrode, and wherein the membrane is configured to transmit an ultrasonic signal having a second frequency, corresponding to the length, in response to applying a second signal to the first electrode.

10. The transmitter of claim 9, wherein the shape is an oval.

11. The transmitter of claim 9, wherein the shape is a rectangle.

12. The transmitter of claim 9, wherein the transmitter further comprises a third electrode and a fourth electrode coupled to opposite ends of the membrane along the length of the membrane.

13. The transmitter of claim 9, wherein the transmitter further comprises a third electrode and a fourth electrode coupled to opposite ends of the membrane along the width of the membrane.

14. The transmitter of claim 9, wherein the transmitter is included within a mobile phone, a tablet computer, a portable media player, or a laptop computer.

15. A method of transmitting at different frequencies using a transmitter comprising a drum, a membrane coupled to the drum, a first electrode coupled to the drum, a second electrode coupled to the membrane, and a plurality of posts of non-uniform height disposed within the drum, the method comprising:

applying a first DC voltage component to the first electrode such that a first post of the plurality of posts causes the membrane to have a first length;

transmitting an ultrasonic signal at a first frequency corresponding to the first length;

applying a second DC voltage component to the first electrode such that a second post of the plurality of posts causes the membrane to have a second length; and

transmitting an ultrasonic signal at a second frequency corresponding to the second length.

16. The method of claim 15, wherein a height of the first post of the plurality of posts is less than a height of the second post of the plurality of posts, and wherein the first post is positioned closer to a center of the membrane than the second post.

17. The method of claim 16, wherein applying the first DC voltage component to the first electrode causes the membrane to contact the first post, and wherein applying the second DC voltage component to the first electrode causes the membrane to contact the second post.

18. The method of claim 15, wherein the membrane is circular in shape, and wherein each of the plurality of posts form concentric circles within the drum.

19. The method of claim 15, wherein the transmitter is a microelectromechanical system (MEMS) transmitter.

20. The method of claim 15 wherein the transmitter is enclosed within a housing, and wherein the housing comprises one or more dividers to control flow of air out of the housing.

21. A method of transmitting at different frequencies using a transmitter comprising a drum, a first membrane coupled to the drum, a second membrane coupled to the drum, a first electrode coupled to the drum, a second electrode coupled to the first membrane, a third electrode coupled to the first membrane opposite the second electrode, and a fourth electrode coupled to the second membrane, the method comprising:

applying a first DC voltage component to the third electrode such that the first membrane is separate from the second membrane; and

applying a second DC voltage component to the third electrode such that the first membrane and second membrane are coupled together.

22. The method of claim 21, further comprising:

transmitting an ultrasonic signal having a first frequency when the signal having the first DC voltage component is applied to the third electrode; and

transmitting an ultrasonic signal having a second frequency when the signal having the second DC voltage component is applied to the third electrode.