Method and apparatus for improving performance of digital microelectromechanical systems microphones

Patent metadata

Field	Value
Publication number	US-9716933-B2
Application number	US-201514719507-A
Country	US
Kind code	B2
Filing date	May 22, 2015
Priority date	May 22, 2015
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

A microphone device comprising a microelectromechanical systems (MEMS) acoustic sensors, an automatic gain compensation (AGC) component, and a direct current (DC) offset cancellation component is described. An microphone device can be configured for AGC of an analog gain stage or a digital gain stage associated with the MEMS acoustic sensor. Provided implementations can also be configured to compensate DC offset resulting from adjustment of the analog provided by the AGC component. Additional embodiments of the subject disclosure can provide digital frequency equalization and/or linearization.

First claim

What is claimed is:

1. A digital microphone device, comprising:
a microelectromechanical systems (MEMS) acoustic sensor configured to receive an acoustic signal;
an amplifier configured to receive a signal the MEMS acoustic sensor to create an amplified signal;
an analog-to-digital converter (ADC) that converts the amplified signal into a digital signal;
an automatic gain compensation (AGC) component configured for automatic gain control of at least one of an analog gain stage or a digital gain stage associated with the MEMS acoustic sensor; and
a direct current (DC) offset cancellation component configured to compensate for at least one adjustment of the at least one of the analog gain stage or the digital gain stage determined by the AGC component.

2. The digital microphone device of claim 1 , wherein the at least one adjustment of the at least one of the analog gain stage or the digital gain stage is configured to be dynamically applied based on a characteristic of the acoustic signal to facilitate a high dynamic range associated with the digital microphone device.

3. The digital microphone device claim 1 , wherein the at least one adjustment of the at least one of the analog gain stage or the digital gain stage is configured to be applied below audible range for humans.

4. The digital microphone device of claim 1 , wherein the at least one adjustment of the at least one of the analog gain stage is configured to be applied in an increment of a rational number of the form k/2 N , where k and N are integer numbers.

5. The digital microphone device of claim 1 , wherein the AGC component further comprises at least one of a set of unit resistors or a set of unit capacitors configured to facilitate applying the at least one adjustment of the at least one of the analog gain stage.

6. The digital microphone device of claim 1 , further comprising:
a passive attenuator configured to receive the signal from the MEMS acoustic sensor and to provide an attenuated signal to the amplifier.

7. The digital microphone device of claim 6 , wherein the passive attenuator comprises a capacitive divider.

8. The digital microphone device of claim 1 , wherein the AGC component is further configured to apply the at least one adjustment of the at least one of the analog gain stage or the digital gain stage comprising a digital gain adjustment substantially equal to an analog attenuation.

9. The digital microphone device of claim 1 , further comprising:
a pulse-density modulation (PDM) signal generator adapted to be configured dynamically based in part on the at least one adjustment of the at least one of the analog gain stage or the digital gain stage determined by the AGC component.

10. The digital microphone device of claim 9 , wherein an order of the PDM signal generator is changed dynamically based in part on the at least one adjustment.

11. The digital microphone device of claim 1 , further comprising:
a digital frequency equalizer component configured to compensate for distortion in the frequency response of the MEMS acoustic sensor.

12. The digital microphone device of claim 11 , further comprising:
a frequency response characterization self-test component.

13. The digital microphone device of claim 1 , further comprising:
a digital linearizer component configured to compensate for non-linearity of at least one of the MEMS acoustic sensor or the analog gain stage.

14. The digital microphone device of claim 13 , further comprising:
a non-linearity characterization self-test component.

15. The digital microphone device of claim 1 , further comprising;
a memory configured to store information associated with at least one of the AGC component, frequency equalization, or non-linearity compensation.

16. A system, comprising:
a digital microelectromechanical systems (MEMS) microphone comprising an automatic gain compensation (AGC) component configured for automatic gain control of at least one of an analog gain stage or a digital gain stage associated with the digital MEMS microphone and a direct current (DC) offset cancellation component configured to compensate for at least one adjustment of the at least one of the analog gain stage or the digital gain stage determined by the AGC component;
at least one of a digital frequency equalizer component configured to compensate for distortion in the frequency response of the digital MEMS microphone or a digital linearizer component configured to compensate for non-linearity of at least one of a MEMS transducer associated with the digital MEMS microphone or the analog gain stage;
a memory configured to store information associated with at least one of the AGC component, frequency equalization, or non-linearity compensation to facilitate operation of the digital MEMS microphone; and
an output component configured to transmit a digital signal associated with the digital MEMS microphone comprising at least one of a pulse-density modulation (PDM) signal, integrated interchip sound (I2S) signal, or a Soundwire signal.

17. The system of claim 16 , further comprising:
embedded self-test circuitry configured to determine and store information associated with at least one of frequency equalization or nonlinearity compensation.

18. The system of claim 16 , further comprising:
a pulse-density modulation (PDM) signal generator configured dynamically based in part on the at least one adjustment of the at least one of the analog gain stage or the digital gain stage determined by the AGC component.

19. The system of claim 16 , wherein the at least one adjustment of the at least one of the analog gain stage or the digital gain stage is configured to be applied below audible range for humans.

20. A method, comprising:
transducing an acoustic signal with a microelectromechanical systems (MEMS) acoustic sensor to produce an analog signal;
determining at least one adjustment of at least one of an analog gain stage or a digital gain stage associated with the MEMS acoustic sensor with an automatic gain compensation (AGC) component;
adjusting at least one of the analog gain stage or the digital gain stage associated with the MEMS acoustic sensor with the AGC component based at least in part on the at least one adjustment;
compensating for the at least one adjustment with a direct current (DC) offset cancellation component configured for compensation of the at least one adjustment of the at least one of the analog gain stage or the digital gain stage determined by the AGC component; and
outputting a digital signal associated with the analog signal, comprising at least one of a pulse-density modulation (PDM) signal, integrated interchip sound (I2S) signal, or a Soundwire signal, based at least in part on the at least one adjustment and the compensation.

21. The method of claim 20 , wherein the adjusting comprises adjusting at a rate below audible range for humans.

22. The method of claim 20 , further comprising:
dynamically changing an order of a PDM signal generator associated with the digital signal based in part on the at least one adjustment of the at least one of the analog gain stage or the digital gain stage determined by the AGC component.

23. The method of claim 20 , further comprising:
performing at least one of digital frequency equalization of the digital signal to compensate for distortion in the frequency response associated with the MEMS acoustic sensor or digital linearization on the digital signal to compensate

Assignees

• Invensense Inc

Inventors

• Oliaei Omid

Classifications

• H04R3/00

  Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F) · CPC title

• H04R2201/003

  Mems transducers or their use · CPC title

• H03G3/3005 Primary

  in amplifiers suitable for low-frequencies, e.g. audio amplifiers (H03G3/32, H03G3/34 take precedence) · CPC title

• H04R1/08 Primary

  Mouthpieces; {Microphones;} Attachments therefor · CPC title

• H04R19/04

  Microphones (H04R19/01 takes precedence) · CPC title