MEMS based acoustic array

• US 7,092,539 B2
• Filed: 11/28/2001
• Issued: 08/15/2006
• Est. Priority Date: 11/28/2000
• Status: Active Grant

• Current Assignee: NASA Langley Research Center (Government of the United States of America), University of Florida Research Foundation, Incorporated (State University System of Florida)
• Original Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Inventors: Arnold, David P., Humphreys, William M., Nishida, Toshikazu, Sheplak, Mark
• Primary Examiner(s): Grier, Laura A.
• Application Number:
  US09/997,113
• Publication Number:
  US 20020149070A1
• Time in Patent Office: 1,721 Days
• Field of Search: None
• US Class Current: 381/114
• CPC Class Codes: G01H 11/08 using piezoelectric devices
• CPC Class Codes: H04R 2430/23 Direction finding using a sum-delay beam-former
• CPC Class Codes: H04R 29/006 Microphone matching
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

Embodiments of the present invention described and shown in the specification and drawings include a combination responsive to an acoustic wave that can be utilized as a dynamic pressure sensor. In one embodiment of the present invention, the combination has a substrate having a first surface and an opposite second surface, a microphone positioned on the first surface of the substrate and having an input and a first output and a second output, wherein the input receives a biased voltage, and the microphone generates an output signal responsive to the acoustic wave between the first output and the second output. The combination further has an amplifier positioned on the first surface of the substrate and having a first input and a second input and an output, wherein the first input of the amplifier is electrically coupled to the first output of the microphone and the second input of the amplifier is electrically coupled to the second output of the microphone for receiving the output signal from the microphone. The amplifier is spaced from the microphone with a separation smaller than 0.5 mm.

Claims

1. A printed circuit board array responsive to aeroacoustic waves, comprising:

a. a printed circuit board having a first surface and an opposing second surface;

b. a plurality of sockets distributed over the first surface of the printed circuit board;

c. a plurality of microphone packages, wherein each microphone package is received in a corresponding socket and contains at least one microphone responsive to an aeroacoustic wave, each of said microphones including a semiconductor substrate, a cavity formed in said substance, a diaphragm covering said cavity, and a vent channel in fluid communication with said cavity and an atmosphere surrounding said array, and

d. at least one signal processor disposed on said circuit board, an input of said signal processor coupled to output of said plurality microphone packages, said processor beamforming signals received from said plurality of microphone packages and outputting a combined signal therefrom.

2. The printed circuit board array of claim 1, further comprising a laser diode positioned on the first surface of the printed circuit board for aiming the printed circuit board array toward a source of the aeroacoustic wave.

3. The printed circuit board array of claim 1, further comprising a piezoresistive layer on said diaphragm, wherein said microphone is a piezoresistive microphone.

4. The printed circuit board array of claim 1, further comprising at least one support layer positioned below the second surface of the printed circuit board.

5. The printed circuit board array of claim 4, wherein each of the support layers comprises a garolite stiffening layer.

6. The printed circuit board array of claim 5, wherein each of the garolite stiffening layer is bonded to the printed circuit board.

7. The printed circuit board array of claim 1, wherein the printed circuit board comprises a double-sided copper clad.

8. The printed circuit board array of claim 1, wherein the printed circuit board has a center, and the plurality of microphone packages are distributed over the first surface of the printed circuit board along a plurality of concentric rings, each ring having a radius measured from the center of the printed circuit board different from the radius of any other ring.

9. The printed circuit board array of claim 8, wherein an equal number of the microphone packages are distributed over each ring.

10. The printed circuit board array of claim 1, wherein each microphone package includes at least one amplifier coupled to and spaced from the microphone with a separation smaller than 0.5 mm.

11. The printed circuit board array of claim 10, wherein the microphone is a piezoresistive microphone.

12. The printed circuit board array of claim 10, wherein:

a. said semiconductor substrate has a first surface and a second surface;

b. said microphone positioned on the first surface of the semiconductor substrate and having an input and a first output and a second output, wherein the input receives a biased voltage, and the microphone generates an output signal responsive to the aeroacoustic

wave between the first output and the second output;

c. an amplifier positioned on the first surface of the semiconductor substrate and having a first input and a second input and an output, wherein the first input of the amplifier is electrically coupled to the first output of the microphone and the second input of the amplifier is electrically coupled to the second output of the microphone for receiving the output signal from the microphone;

d. a first capacitor and a first resistor forming a first RC pair positioned on the first surface of the semiconductor substrate and being electrically coupled between the first input of the amplifier and the first output of the microphone; and

e. a second capacitor and a second resistor forming a second RC pair positioned on the first surface of the semiconductor substrate and being electrically coupled between the second input of the amplifier and the second output of the microphone,

wherein the output signal from the microphone has a DC component and an AC component, and the first and second RC pairs substantially block the DC component and allow the AC component of the output signal from the microphone to pass, thereby to allow the amplifier to generate a low impedance signal at the output, and wherein the amplifier is spaced from the microphone with a separation smaller than 0.5 mm.

13. The printed circuit board array of claim 12, wherein the microphone comprises four piezoresistors forming a Wheatstone bridge that has a first arm, an opposing second arm, a third arm, and an opposing fourth arm, the first arm being electrically coupled to the input of the microphone, the opposing second arm being electrically coupled to ground, the third arm being electrically coupled to the first input of the amplifier, and the opposing fourth arm being electrically coupled to the second input of the amplifier.

14. The printed circuit board array of claim 13, wherein the first capacitor is electrically coupled in series between the third arm of the Wheatstone bridge and the first input of the amplifier, and the first resistor is electrically coupled in parallel between the second arm of the Wheatstone bridge and the capacitor.

15. The printed circuit board array of claim 14, wherein the second capacitor is electrically coupled in series between the fourth arm of the Wheatstone bridge and the second input of the amplifier, and the second resistor is electrically coupled in parallel between the second arm of the Wheatstone bridge and the capacitor.

16. The printed circuit board array of claim 15, wherein the first resistor and the second resistor are jointly coupled to the second arm of the Wheatstone bridge.

17. The printed circuit board array of claim 16, wherein the semiconductor substrate comprises a silicon layer.

18. The printed circuit board array of claim 17, wherein the microphone package further comprises:

a. a package body positioned underneath the semiconductor substrate for supporting the semiconductor substrate; and

b. a peripheral portion extending away from the package body.

19. The printed circuit board array of claim 18, wherein the package body is electrically coupled to ground for electromagnetic shielding.

20. The printed circuit board array of claim 18, wherein the microphone package further comprises a lid positioned above the semiconductor substrate.

21. The printed circuit board array of claim 20, wherein the lid comprises:

a. a body; and

b. a peripheral portion extending away from the body,

wherein the body is complementarily sized such that when the lid is positioned over the semiconductor substrate, the peripheral portion of the lid matches to and supported by the peripheral portion of the package, and the body covers the semiconductor substrate and components positioned on the semiconductor substrate.

22. The printed circuit board array of claim 21, wherein the lid is made from a material that is substantially transparent to the aeroacoustic wave.

23. The printed circuit board array of claim 21, wherein the lid is electrically coupled to ground for electromagnetic shielding.