Microelectromechanics-based frequency signature sensor

• US 5,856,722 A
• Filed: 12/23/1996
• Issued: 01/05/1999
• Est. Priority Date: 01/02/1996
• Status: Expired due to Term

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: Haronian, Dan, MacDonald, Noel C.
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US08/771,681
• Time in Patent Office: 743 Days
• Field of Search: 310/311, 310/312, 310/321, 310/322, 310/329-332, 310/309
• US Class Current: 310/321
• CPC Class Codes: G01H 3/08 Analysing frequencies present in complex vibrations, e.g. comparing harmonics present acoustic presence detection G01V1/001
• CPC Class Codes: H03H 9/50 Mechanical coupling means

Abstract

An acoustic filter array of microelectromechanical beams each having a characteristic resonance frequency response to mechanical and/or acoustical vibration. The array divides incoming acoustic signals into a plurality of discrete spectral components, each of which may be separately detected and converted into corresponding electrical signals. The acoustic filter may be integrated onto a single crystal silicon substrate with electrical circuity for performing acoustic signal processing functions required for applications such as speech processing and simulating the physiological function of the ear.

Claims

1. A microelectromechanical sensor responsive to vibration, comprising:

an array of microelectromechanical released structural beam elements of different beam characteristics mounted for deflection in response to vibration to be detected, each of said beam elements being acoustically coupled to adjacent ones of said beam elements, and being spaced from adjacent ones of said beam elements by no more than approximately 20 μ

m; and

a transducer for each beam which generates an output signal in response to the deflection of its corresponding beam element.

2. The sensor of claim 1, wherein each said beam element is resonant at a different selected frequency.

3. The sensor of claim 2, wherein said vibration is an acoustic wave impinging on said array and acoustically coupled to said beam element.

4. The sensor of claim 3, wherein said vibration is produced by mechanical motion of a structure, and wherein said array is coupled to said structure and is responsive to said vibration to serve as an accelerometer.

5. The sensor of claim 1, wherein each said beam element includes a first end and a second end each fixed to a substrate.

6. The sensor of claim 5, wherein each said beam includes a central portion released from said substrate for relative motion with respect to the substrate.

7. The sensor of claim 6, wherein said first and second ends of each said beam element are each secured to respective tension-adjusting devices for tuning the resonant frequencies of respective beams.

8. The sensor of claim 6, further including means associated with at least one of said beams for adjusting the resonant frequency of the beam.

9. The sensor of claim 1, wherein the vibration to be detected has a frequency signature to be detected, and wherein said beam elements have resonant frequencies corresponding to frequency components of said frequency signature to produce transducer output signals corresponding to said frequency signature.

10. The sensor of claim 1, wherein said beam elements are each resonant at a different acoustic frequency to form an acousto-mechanical filter.

11. The sensor of claim 1, wherein each of said beam elements is responsive to a selected vibration frequency band to produce a corresponding transducer output signal.

12. The sensor of claim 11, wherein said vibration to be detected has a frequency signature, and wherein said transducer output signals from all of said beam elements represent said frequency signature.

13. The sensor of claim 11, wherein said vibration to be detected is speech, and wherein said transducer output signals from all said beams represent said speech.

14. The sensor of claim 11, wherein said different beam characteristics are beam lengths.

15. The sensor of claim 14, wherein said beams are fabricated from a common material and have substantially the same cross-sections, whereby the response of each beam to a selected frequency band is determined by beam length.

16. The sensor of claim 15, further including means for adjusting the response of each beam to a selected frequency band for tuning said array.

17. The sensor of claim 16, wherein said means for adjusting includes capacitor means coupled to each said beam.

18. The sensor of claim 14, wherein said array includes multiple beam elements of different lengths, said lengths varying exponentially from one beam to the next.

19. The sensor of claim 1, wherein said array includes a substrate having a cavity, said beam elements each being integral with and fabricated from said substrate and extending into said cavity.

20. The sensor of claim 19, wherein w\said substrate and said beam elements are single crystal silicon.

21. The sensor of claim 20, wherein said beams extend across said cavity and are fixed at opposite ends to said substrate at cavity walls formed during fabrication of said beams.

22. The sensor of claim 21, wherein said beams are generally parallel to each other and lie in a common array plane.

23. The sensor of claim 22, wherein each beam element has a width of about 1 μ

m and a height of about 10 μ

m to provide a high aspect ratio which constrains deflection of the beam element to substantially said common array plane.

24. The sensor of claim 23, wherein said cavity has a floor spaced about 100 μ

m below said beam elements.

25. The sensor of claim 23, wherein said beam elements have a length of greater than 370 μ

m.

26. The sensor of claim 22, wherein each beam element has a width of about 10 μ

m and a height of about 1 μ

m to provide a high aspect ratio which constrains deflection of the beam element to a direction substantially perpendicular to said common array plane.

27. A microelectromechanical sensor responsive to vibration, comprising:

an array of microelectromechanical released structural beam elements of different beam characteristics mounted for deflection in response to vibration to be detected, each said beam element including a first end and a second end each fixed to a substrate, and a central portion released from said substrate for relative motion with respect to the substrate;

a plurality of tension-adjusting devices for tuning the resonant frequencies of respective beams, said first and second ends of each said beam elements being secured to respective ones of said tension-adjusting devices; and

a transducer for each beam which generates an output signal in response to the deflection of its corresponding beam.