Electrical testing and feedthrough cancellation for an acoustic sensor

• US 9,661,433 B2
• Filed: 01/30/2014
• Issued: 05/23/2017
• Est. Priority Date: 01/30/2014
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Salvia, James, Cagdaser, Baris, Khenkin, Aleksey S.
• Primary Examiner(s): Goins, Davetta W
• Assistant Examiner(s): SELLERS, DANIEL R
• Application Number:
  US14/168,983
• Publication Number:
  US 20150289073A1
• Time in Patent Office: 1,209 Days
• Field of Search: 381 58
• CPC Class Codes: G01H 17/00 Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves, not provided for in the preceding groups see provisionally also G01H1/00
• CPC Class Codes: G01V 13/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005
• CPC Class Codes: H04R 29/004 for microphones H04R29/007 takes precedence

Abstract

A method and circuit for testing an acoustic sensor are disclosed. In a first aspect, the method comprises using electro-mechanical features of the acoustic sensor to measure characteristic of the acoustic sensor. In a second aspect, the method comprises utilizing an actuation signal to evaluate mechanical characteristics of the acoustic sensor. In a third aspect, the method comprises using a feedthrough cancellation system to measure a capacitance of the acoustic sensor. In the fourth aspect, the circuit comprises a mechanism for driving an electrical signal into a signal path of the acoustic sensor to cancel an electrical feedthrough signal provided to the signal path, wherein any of the electrical signal and the electrical feedthrough signal are within or above an audio range.

Claims

1. A method for testing an acoustic sensor, the method comprising:

using electro-mechanical features of the acoustic sensor to measure characteristics of the acoustic sensor to facilitate the testing of the acoustic sensor; and

utilizing electrical feedthrough cancellation to cancel out a portion of an electrical signal that is an electrical feedthrough signal, wherein the electrical signal facilitates the testing of the acoustic sensor.

2. The method of claim 1, wherein the electrical feedthrough signal results from an electronically-controlled transduction of a transducer, comprising the acoustic sensor, and wherein, to facilitate improving accuracy of the testing of the acoustic sensor, the portion of the electrical signal that is the electrical feedthrough signal is canceled out without canceling another portion of the electrical signal that facilitates actuation of the acoustic sensor.

3. The method of claim 1, further comprising:

utilizing actuation to electronically evaluate sensitivity of the acoustic sensor to acoustic signals.

4. The method of claim 3, wherein the utilizing the actuation comprises at least one of applying magnetic, thermal, or piezoelectric forces to the acoustic sensor to generate a response.

5. The method of claim 3, wherein the utilizing the actuation comprises applying an electrostatic force to the acoustic sensor to generate the response.

6. The method of claim 5, further comprising:

estimating the sensitivity of the acoustic sensor to acoustic signals based on the response to the electrostatic force.

7. The method of claim 1, wherein the acoustic sensor is a micro-electro-mechanical systems (MEMS) microphone.

8. The method of claim 1, wherein the testing is implemented as a routine during manufacture of the acoustic sensor.

9. The method of claim 1, wherein the testing is implemented during a lifetime of the acoustic sensor.

10. The method of claim 1, wherein the testing is implemented after the acoustic sensor is integrated into an end product.

11. The method of claim 1, wherein the characteristics include a capacitance of the acoustic sensor.

12. The method of claim 11, wherein the capacitance is measured at a frequency at which a mechanical response of the acoustic sensor is diminished to facilitate reducing a mechanical response associated with motion of the acoustic sensor to facilitate determining the electrical feedthrough signal.

13. The method of claim 12, further comprising:

reducing the mechanical response by utilizing a cancellation actuation to facilitate reducing an actuation associated with the acoustic sensor.

14. The method of claim 13, wherein the another actuation comprises at least one of thermal, magnetic, piezoelectric, or electrostatic forces.

15. The method of claim 12, further comprising:

reducing the mechanical response by utilizing mechanical stops to reduce motion of the acoustic sensor when engaged.

16. The method of claim 11, further comprising:

estimating the capacitance based on a measurement of the electrical feedthrough cancellation.

17. The method of claim 1, wherein the testing is utilized to determine other properties of the acoustic sensor that include at least one of an electrical gap or a mechanical gap between electrodes of the acoustic sensor.

18. A method for testing an acoustic sensor, the method comprising:

utilizing an actuation signal to evaluate mechanical characteristics of the acoustic sensor wherein the actuation signal is used to facilitate actuation of the acoustic sensor; and

utilizing electrical feedthrough cancellation to cancel out a portion of the actuation signal that is an electrical feedthrough signal.

19. The method of claim 18, wherein the actuation signal comprises a pulse.

20. The method of claim 18, wherein the electrical feedthrough signal results from an electronically-controlled transduction of the acoustic sensor, and wherein, to facilitate improving accuracy of the testing of the acoustic sensor, the portion of the actuation signal that is the electrical feedthrough signal is canceled out without canceling another portion of the actuation signal that facilitates actuation of the acoustic sensor.

21. The method of claim 18, wherein the mechanical characteristics include at least one of a frequency response, an impulse response, a resonant frequency, a spring constant, a damping, a mass, or a quality factor.

22. The method of claim 18, wherein the actuation signal comprises of at least one magnetic, thermal, or piezoelectric forces.

23. The method of claim 18, wherein the actuation signal comprises an electrostatic force.

24. The method of claim 23, wherein the electrostatic force is substantially changed in magnitude over a time period that is shorter than a mechanical response time constant of the acoustic sensor.

25. The method of claim 23, further comprising:

determining a frequency response of the acoustic sensor based on a response to a change in the electrostatic force.

26. The method of claim 18, wherein the testing is implemented as a routine during manufacture of the acoustic sensor.

27. The method of claim 18, wherein the testing is implemented during a lifetime of the acoustic sensor.

28. The method of claim 18, wherein the testing is implemented after the acoustic sensor is integrated into an end product.