Electrostatically tunable resonance frequency beam utilizing...

Measuring and testing – Speed – velocity – or acceleration – Acceleration determination utilizing inertial element

Reexamination Certificate

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C073S514340, C073S514260, C310S309000, C361S280000

Reexamination Certificate

active

06263736

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to methods and apparatus for detecting particular frequencies of vibration, and especially for detecting and selecting particular frequencies of vibration using detection and selection apparatus comprising electrostatically-tunable beam members such as cantilevers and very small cantilevers, often called microcantilevers.
BACKGROUND OF THE INVENTION
The resonance frequencies of a beam occur at discrete values based on the geometrical and mechanical properties of the beam and the environment in which it is located. The efficiency of resonance is measured by the quality factor (or Q-factor), where large Q-factors correspond to high efficiency. High-Q beams such as cantilever beams can be used as efficient listening devices for particular frequencies, with much higher sensitivity and specificity for particular acoustic bands of interest in comparison to conventional acoustic transducers. Moreover, microcantilevers, which are only a few hundred microns in length, are also much more simple to produce and could be far smaller in comparison to standard microphone technologies. As an inevitable consequence of their high specificity, one would need an exorbitant number of fixed-frequency cantilevers to cover a broad frequency spectrum. Because of this simple reason cantilever-based listening devices have not attracted significant attention. Thus, it is desirable to make a high-Q cantilever that uses an electrostatic method to achieve broad frequency tunability. The resonance frequency of such a cantilever might be changed by varying an electrical charge, potential or voltage (hereinafter referred to as potential) and thereby varying electrostatic attraction or repulsion (hereinafter referred to as electrostatic force) acting upon the cantilever.
OBJECTS OF THE INVENTION
Accordingly, it is an object of the present invention to provide a new and improved method and apparatus for tuning the resonance frequency of a beam such as a cantilever element, and more specifically to provide a new method and apparatus for tuning the resonance frequency of a beam such as a cantilever element by varying a voltage applied to the beam.
Further and other objects of the present invention will become apparent from the description contained herein.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, the foregoing and other objects are achieved by an electrostatically-tunable beam for detecting a particular frequency of acoustic vibration and for selecting a particular frequency of acoustic vibration out of a mixture of frequencies which comprises: a beam element having an end and a surface, and being fixedly disposed on the end; a stress-sensitive means for sensing stress selected from the group consisting of: a stress sensitive coating having a stiffness that varies with the stress therein affixed on the surface of the beam element and the beam element material having a stiffniess that varies with the stress therein; a first electrical conductor means for conducting electricity selected from the group consisting of: an electrically conductive coating disposed on a surface of the beam element and the electrical conductivity of the beam element material; a second electrical conductor means for conducting electricity fixedly disposed generally parallel to the first electrical conductor means and separated from the first electrical conductor means by a gap formed therebetween; electrical potential means suitably disposed and connected for providing electrical potentials upon the first electrical conductor means and the second electrical conductor means to cause electrostatic force between the first electrical conductor means and the second electrical conductor means whereby electrostatic force therebetween causes the beam element to bend, thereby producing a change in stress in the stress-sensitive means and a change in the resonance frequency of the electrostatically-tunable beam.
In accordance with a second aspect of the present invention, the foregoing and other objects are achieved by a method for detecting a particular frequency of acoustical vibration in a mixture of frequencies which comprises the steps of: providing an electrostatically-tunable beam comprising a beam element having an end and a surface and being fixedly disposed on the end; a stress-sensitive means for sensing stress selected from the group consisting of: a stress sensitive coating having a stiffness that varies with the stress therein affixed on the surface of the beam element and the beam element material having a stiffness that varies with the stress therein; a first electrical conductor means for conducting electricity selected from the group consisting of: an electrically conductive coating disposed on a surface of the beam element and the electrical conductivity of the beam element material; a second electrical conductor means for conducting electricity fixedly disposed generally parallel to the first electrical conductor means and separated from the first electrical conductor means by a gap formed therebetween; and electrical potential means suitably disposed and connected for providing electrical potentials upon the first electrical conductor means and the second electrical conductor means; exposing the beam element to the mixture of frequencies; activating the electrical potential means to cause electrostatic force between the first electrical conductor means and the second electrical conductor means whereby electrostatic force therebetween causes the beam element to bend thereby producing a change in stress in the stress-sensitive means and a change in the resonance frequency of the electrostatically-tunable beam to permit the electrostatically-tunable beam to respond resonantly at the particular frequency; and determining from the resonance response of the electrostatically-tunable beam whether the particular frequency of vibration is detected.
In accordance with a third aspect of the present invention, the foregoing and other objects are achieved by a method for selecting a desired frequency of acoustical vibration from a mixture of frequencies which comprises the steps of: providing an electrostatically-tunable beam comprising a beam element having an end and a surface, and being fixedly disposed on the end; a stress-sensitive means for sensing stress selected from the group consisting of: a stress sensitive coating having a stiffness that varies with the stress therein affixed on the surface of the beam element and the beam element material having a stiffniess that varies with the stress therein; a first electrical conductor means for conducting electricity selected from the group consisting of: an electrically conductive coating disposed on a surface of the beam element and the electrical conductivity of the beam element material; a second electrical conductor means for conducting electricity fixedly disposed generally parallel to the first electrical conductor means and separated from the first electrical conductor means by a gap formed therebetween; and electrical potential means suitably disposed and connected for providing electrical potentials upon the first electrical conductor means and the second electrical conductor means; activating the electrical potential means to cause electrostatic force between the first electrical conductor means and the second electrical conductor means whereby electrostatic force therebetween causes the beam element to bend thereby producing a change in stress in the stress-sensitive means and a change in the resonance frequency of the electrostatically-tunable beam to establish the resonance frequency of the electrostatically-tunable beam at the desired frequency; and exposing the electrostatically-tunable beam to the mixture of frequencies to excite the electrostatically-tunable beam to vibrate at a desired resonance frequency whereby the particular frequency desired is selected out of the mixture of frequencies.


REFERENCES:
patent: 5211051 (1993-05-01), Kaiser et al.
patent: 5267471 (1993-12-01), Ab

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