Electrical testing and feedthrough cancellation for an acoustic sensor

• US 10,587,969 B2
• Filed: 05/17/2017
• Issued: 03/10/2020
• 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:
  US15/598,214
• Publication Number:
  US 20170251316A1
• Time in Patent Office: 1,028 Days
• 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, comprising:

applying a signal waveform of a defined frequency to an acoustic sensor to mitigate a mechanical response of the acoustic sensor, wherein the acoustic sensor generates an electrical signal in response to the signal waveform; and

performing electrical feedthrough cancellation to cancel out a portion of the electrical signal that is an electrical feedthrough signal to facilitate determining a sensitivity of the acoustic sensor.

2. The method of claim 1, wherein the performing the electrical feedthrough cancellation comprises adjusting a converter component to reduce a voltage level of the electrical signal generated by the acoustic sensor to facilitate canceling out the electrical feedthrough signal.

3. The method of claim 1, further comprising:

determining a frequency of the signal waveform of a set of frequencies of the signal waveform that mitigates the mechanical response of the acoustic sensor, wherein the frequency is the defined frequency; and

selecting the defined frequency.

4. The method of claim 1, further comprising:

discontinuing the applying of the signal waveform; and

applying an audio waveform to the acoustic sensor to facilitate generating motion of the acoustic sensor.

5. The method of claim 4, further comprising:

determining an output signal generated by the acoustic sensor in response to the applying of the audio waveform to the acoustic sensor, wherein the determining the sensitivity of the acoustic sensor comprises determining the sensitivity of the acoustic sensor as a function of the output signal.

6. The method of claim 4, further comprising:

determining an output signal generated by the acoustic sensor in response to the applying of the audio waveform to the acoustic sensor; and

determining a voltage level at an output of a charge pump associated with the acoustic sensor, wherein the determining the sensitivity of the acoustic sensor comprises determining the sensitivity of the acoustic sensor as a function of the output signal and the voltage level.

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

8. A method, comprising:

driving a signal waveform of a defined frequency into an acoustic sensor to facilitate diminishing a mechanical response of the acoustic sensor, wherein the acoustic sensor generates an electrical signal in response to the signal waveform; and

performing electrical feedthrough cancellation to cancel out a portion of the electrical signal that is an electrical feedthrough signal to facilitate determining a mechanical parameter of the acoustic sensor.

9. The method of claim 8, wherein the performing the electrical feedthrough cancellation comprises adjusting a converter component to diminish a voltage level of the electrical signal generated by the acoustic sensor to facilitate canceling out the electrical feedthrough signal.

10. The method of claim 8, further comprising:

determining a frequency of the signal waveform of a set of frequencies of the signal waveform that diminishes the mechanical response of the acoustic sensor, wherein the frequency is the defined frequency; and

selecting the defined frequency for the signal waveform.

11. The method of claim 8, further comprising:

ceasing the driving of the signal waveform into the acoustic sensor; and

driving an electrostatic pulse to the acoustic sensor to facilitate generating an impulse response of the acoustic sensor.

12. The method of claim 11, further comprising:

determining a time duration of the electrostatic pulse that is smaller than mechanical time constants associated with the acoustic sensor that are determined to be dominant; and

selecting the time duration of the electrostatic pulse, wherein the driving the electrostatic pulse to the acoustic sensor comprises driving the electrostatic pulse to the acoustic sensor for the time duration.

13. The method of claim 11, further comprising:

in response to the driving of the electrostatic pulse into the acoustic sensor, determining the impulse response at an output of the acoustic sensor; and

extracting one or more mechanical parameters, comprising the mechanical parameter, based at least in part on the impulse response.

14. The method of claim 13, further comprising:

converting the impulse response to the frequency domain to generate a converted impulse response based at least in part on a Fast Fourier Transform, wherein the one or more mechanical parameters comprise at least one of a resonant frequency associated with the acoustic sensor or a quality factor associated with the acoustic sensor.

15. A device, comprising:

an electrostatic force generator that applies a signal waveform of a defined frequency to an acoustic sensor to mitigate a mechanical response of the acoustic sensor, wherein the acoustic sensor generates an electrical signal in response to the signal waveform; and

an electrical feedthrough cancellation component that performs electrical feedthrough cancellation to cancel out a portion of the electrical signal that is an electrical feedthrough signal to facilitate a determination of one or more characteristics of the acoustic sensor.

16. The device of claim 15, wherein the one or more characteristics comprises at least one of a sensitivity of the acoustic sensor or one or more mechanical parameters of the acoustic sensor, and wherein the one or more mechanical parameters comprise at least one of a resonant frequency associated with the acoustic sensor or a quality factor associated with the acoustic sensor.

17. The device of claim 15, further comprising a converter component that is adjusted to reduce a voltage level of the electrical signal generated by the acoustic sensor to facilitate canceling out the electrical feedthrough signal.

18. The device of claim 15, wherein the electrostatic force generator discontinues the application of the signal waveform into the acoustic sensor and applies an audio waveform to the acoustic sensor to facilitate generation of an output signal by the acoustic sensor, and wherein the device further comprises:

a test component that determines a voltage level at an output of a charge pump associated with the acoustic sensor, wherein the one or more characteristics of the acoustic sensor comprises a sensitivity of the acoustic sensor, and wherein the sensitivity of the acoustic sensor is determined based at least in part on the output signal and the voltage level.

19. The device of claim 15, wherein the electrostatic force generator discontinues the application of the signal waveform into the acoustic sensor and applies an electrostatic pulse to the acoustic sensor to facilitate generation of an impulse response at an output of the acoustic sensor, wherein the one or more characteristics of the acoustic sensor are determined based at least in part on the impulse response, and wherein the one or more characteristics of the acoustic sensor comprise one or more mechanical parameters of the acoustic sensor comprising at least one of a resonant frequency associated with the acoustic sensor or a quality factor associated with the acoustic sensor.

20. The device of claim 15, wherein the device comprises a micro-electro-mechanical systems (MEMS) microphone that comprises the acoustic sensor.