Absolute sensitivity of a MEMS microphone with capacitive and piezoelectric electrodes

Patent metadata

Field	Value
Publication number	US-9894453-B2
Application number	US-201715589340-A
Country	US
Kind code	B2
Filing date	May 8, 2017
Priority date	Dec 15, 2015
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

Microphone systems and methods of determining absolute sensitivities of a MEMS microphone. The microphone system includes a speaker, a MEMS microphone, and a controller. The speaker is configured to generate an acoustic pressure. The MEMS microphone includes a capacitive electrode, a piezoelectric electrode, and a backplate. The capacitive electrode is configured to generate a first capacitive response based on the acoustic pressure and generate a first mechanical pressure based on a capacitive control signal. The piezoelectric electrode is coupled to the capacitive electrode. The piezoelectric electrode is configured to generate a first piezoelectric response signal based on the acoustic pressure and generate a second piezoelectric response signal based on the first mechanical pressure. The controller is configured to generate the capacitive control signal and determine an absolute sensitivity of the capacitive electrode based on the first capacitive response, the first piezoelectric response signal, and the second piezoelectric response signal.

First claim

What is claimed is:

1. A microphone system comprising:
a speaker configured to generate acoustic pressure;
a micro-electro-mechanical system (MEMS) microphone including
a capacitive electrode configured to
generate a first capacitive response based on the acoustic pressure, and
generate a first mechanical pressure based on a capacitive control signal,

a piezoelectric electrode coupled to the capacitive electrode and configured to
generate a first piezoelectric response signal based on the acoustic pressure, and
generate a second piezoelectric response signal based on the first mechanical pressure, and

a backplate positioned parallel to the capacitive electrode; and

a controller configured to
generate the capacitive control signal, and
determine an absolute sensitivity of the capacitive electrode based on the first capacitive response, the first piezoelectric response signal, and the second piezoelectric response signal.

2. The microphone system according to claim 1 , wherein the controller is further configured to generate a piezoelectric control signal, and wherein the piezoelectric electrode is further configured to generate a second mechanical pressure based on the piezoelectric control signal.

3. The microphone system according to claim 2 , wherein the capacitive electrode is further configured to generate a second capacitive response based on the second mechanical pressure.

4. The microphone system according to claim 3 , wherein the controller is further configured to determine an absolute sensitivity of the piezoelectric electrode based at least in part on the first capacitive response, the second capacitive response, and the first piezoelectric response signal.

5. The microphone system according to claim 1 , wherein the controller is further configured to generate a speaker control signal, and wherein the speaker generates the acoustic pressure based on the speaker control signal.

6. The microphone system according to claim 1 , wherein the backplate is positioned on a first side of the capacitive electrode, wherein the piezoelectric electrode is positioned on a second side of the capacitive electrode, and wherein the second side of the capacitive electrode is opposite from the first side of the capacitive electrode.

7. A method of determining absolute sensitivities of a micro-electro-mechanical system (MEMS) microphone, the MEMS microphone including a capacitive electrode, a piezoelectric electrode coupled to the capacitive electrode, and a backplate, the method comprising:
generating acoustic pressure with a speaker;
generating a first capacitive response with the capacitive electrode based on the acoustic pressure;
generating a first piezoelectric response with the piezoelectric electrode based on the acoustic pressure;
generating a capacitive control signal with a controller;
generating a first mechanical pressure with the capacitive electrode based on the capacitive control signal;
generating a second piezoelectric response with the piezoelectric electrode based on the first mechanical pressure; and
determining an absolute sensitivity of the capacitive electrode with the controller based in part on the first capacitive response, the first piezoelectric response, and the second piezoelectric response.

8. The method according to claim 7 , wherein the method further comprises
generating a piezoelectric control signal with the controller; and
generating a second mechanical pressure with the piezoelectric electrode based on the piezoelectric control signal.

9. The method according to claim 8 , wherein the method further comprises
generating a second capacitive response with the capacitive electrode based on the second mechanical pressure.

10. The method according to claim 9 , wherein the method comprises
determining an absolute sensitivity of the piezoelectric electrode with the controller based at least in part on the first capacitive response, the second capacitive response, and the first piezoelectric response.

11. The method according to claim 7 , wherein the method further comprises generating a speaker control signal with the controller, and wherein the speaker generates the acoustic pressure based on the speaker control signal.

12. A microphone system comprising:
a speaker configured to generate an acoustic pressure;
a micro-electro-mechanical system (MEMS) microphone including
a movable membrane having
a capacitive electrode configured to
generate a first capacitive response based on the acoustic pressure, and
generate a first mechanical pressure based on a capacitive control signal, and

a piezoelectric electrode configured to
generate a first piezoelectric response signal based on the acoustic pressure, and
generate a second piezoelectric response signal based on the first mechanical pressure, and

a backplate positioned on the capacitive electrode; and

a controller configured to
generate the capacitive control signal, and
determine an absolute sensitivity of the capacitive electrode based in part on the first capacitive response, the first piezoelectric response signal, and the second piezoelectric response signal.

13. The microphone system according to claim 12 , wherein the controller is further configured to generate a piezoelectric control signal, and wherein the piezoelectric electrode is further configured to generate a second mechanical pressure based on the piezoelectric control signal.

14. The microphone system according to claim 13 , wherein the capacitive electrode is further configured to generate a second capacitive response based on the second mechanical pressure.

15. The microphone system according to claim 14 , wherein the controller is further configured to determine an absolute sensitivity of the piezoelectric electrode based in part on the first capacitive response, the second capacitive response, and the first piezoelectric response signal.

16. The microphone system according to claim 12 , wherein the controller is further configured to generate a speaker control signal, and wherein the speaker generates the acoustic pressure based on the speaker control signal.

17. The microphone system according to claim 12 , wherein the backplate is positioned on a first side of the capacitive electrode, wherein the piezoelectric electrode is positioned on a second side of the capacitive electrode, and wherein the second side of the capacitive electrode is opposite from the first side of the capacitive electrode.

Assignees

• Bosch Gmbh Robert

Inventors

• Doller Andrew

Classifications

• H04R29/004 Primary

  for microphones (H04R29/007 takes precedence) · CPC title

• H04R2201/003

  Mems transducers or their use · CPC title

• H04R23/006

  using solid state devices (solid state devices per se H10) · CPC title

• H04R23/02

  Transducers using more than one principle simultaneously · CPC title

• H04R17/02

  Microphones · CPC title