Micromechanical apparatus with limited actuation bandwidth
First Claim
1. A micromechanical sensing apparatus, comprising:
- a micromechanical sensor including a stationary element and a movable element which are electrically conductive;
a force balance loop coupled to said micromechanical sensor for generating an output indicative of a sensed quantity and for electrostatically controlling a position of said movable element relative to said stationary element, said force balance loop having a prescribed closed loop bandwidth; and
a circuit coupled to said micromechanical sensor for applying to the sensor an actuation signal for electrostatically deflecting said movable element relative to said stationary element, said actuation signal having a maximum amplitude, said circuit including circuitry for limiting the bandwidth of said actuation signal such that said force balance loop controls deflection of said movable element within maximum deflection limits selected to avoid electrostatic capture or contact between said movable element and said stationary element.
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Abstract
A micromechanical sensing apparatus includes a micromechanical sensor having a stationary element and a movable element which are electrically conductive, and a sensing circuit responsive to the micromechanical sensor for generating an output indicative of a sensed quantity. The sensing circuit may have a closed loop configuration or an open loop configuration. The sensing apparatus further includes an actuation circuit for applying to the micromechanical sensor an actuation signal, such as a test signal, for electrostatically deflecting the movable element relative to stationary element. The actuation circuit includes circuitry for limiting the bandwidth of the actuation signal such that the deflection of the movable element does not exceed maximum deflection limits. In the closed loop configuration, the bandwidth of the actuation signal is preferably limited to less than or equal to the closed loop bandwidth of the sensing circuit. As a result, electrostatic capture and/or contact between the movable element and the stationary element is prevented.
77 Citations
26 Claims
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1. A micromechanical sensing apparatus, comprising:
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a micromechanical sensor including a stationary element and a movable element which are electrically conductive; a force balance loop coupled to said micromechanical sensor for generating an output indicative of a sensed quantity and for electrostatically controlling a position of said movable element relative to said stationary element, said force balance loop having a prescribed closed loop bandwidth; and a circuit coupled to said micromechanical sensor for applying to the sensor an actuation signal for electrostatically deflecting said movable element relative to said stationary element, said actuation signal having a maximum amplitude, said circuit including circuitry for limiting the bandwidth of said actuation signal such that said force balance loop controls deflection of said movable element within maximum deflection limits selected to avoid electrostatic capture or contact between said movable element and said stationary element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A micromechanical sensing apparatus comprising:
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a micromechanical sensor including a stationary element and a movable element which are electrically conductive, said micromechanical sensor having a mechanical resonance frequency; a sensing circuit coupled to said micromechanical sensor for generating a signal indicative of a sensed quantity; and an actuation circuit coupled to said micromechanical sensor for applying to said sensor an actuation signal for electrostatically deflecting said movable element relative to said stationary element, said actuation circuit including circuitry for limiting the bandwidth of said actuation signal to prevent contact between said movable element and said stationary element. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. In micromechanical sensing apparatus comprising a micromechanical sensor including a stationary element and a movable element which are electrically conductive, and a force balance loop coupled to said micromechanical sensor for generating an output indicative of a sensed quantity and for electrostatically controlling a position of said movable element relative to said stationary element, a method for actuating said micromechanical sensing device, comprising:
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applying to the micromechanical sensor an actuation signal for electrostatically deflecting said movable element relative to said stationary element, said actuation signal having a maximum amplitude; and limiting the bandwidth of said actuation signal such that said force balance loop controls deflection of said movable element within maximum deflection limits selected to avoid electrostatic capture or contact between said movable element and said stationary element. - View Dependent Claims (22)
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23. A micromechanical apparatus comprising:
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a micromechanical device including a stationary element and a movable element which are electrically conductive, said micromechanical device having a mechanical resonance frequency; and an actuation circuit coupled to said micromechanical device for applying to said device an actuation signal for electrostatically deflecting said movable element relative to said stationary element, said actuation circuit including circuitry for limiting the bandwidth of said actuation signal to prevent contact between said movable element and said stationary element. - View Dependent Claims (24, 25, 26)
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Specification