Pseudosinusoidal oscillator drive system
First Claim
1. An accelerometer for measuring acceleration along a sensitive axis, comprising:
- a support;
a proof mass;
mounting means for mounting the proof mass to the support such that the proof mass can undergo movement relative to the support along the sensitive axis; and
a transducer for reacting to said movement by producing a signal indicative of acceleration along the sensitive axis, the transducer including;
(a) a resonator comprising a piezoelectric crystal connected between the proof mass and the support and constructed to undergo mechanical vibration at a frequency f that varies with the force applied to the crystal in response to an electrical drive signal having a harmonic component at frequency f, and means for producing an electrical resonator signal corresponding to said mechanical vibration; and
(b) drive circuit means including means for receiving the resonator signal and for producing the drive signal in the form of a periodic pseudosinusoidal staircase function at a fundamental frequency f, the staircase function having N steps and M discrete nonzero amplitude levels per period, M and N being integers greater than 1 with M being less than N, the circuit means including means for producing the M amplitude levels such that predetermined harmonics of the fundamental frequency f are not present in the drive signal.
1 Assignment
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Accused Products
Abstract
A circuit (62, 64) for receiving a periodic input signal at frequency f, and for producing a pseudosinusoidal staircase output signal at a fundamental frequency f from which predetermined harmonics of the fundamental frequency are absent. Also provided are an oscillator in which such a circuit forms the drive circuit for a piezoelectric crystal, and an accelerometer in which such an oscillator is used as the force sensing means. In the accelerometer, the reaction force of a proof mass (40) is sensed by a resonator that comprises a drive circuit (44) for producing a drive signal and a piezoelectric crystal (42) connected between the proof mass and support (46). In response to the drive signal, the crystal undergoes mechanical vibration at a frequency f that varies with the force applied to the crystal. A resonator signal corresponding to the mechanical vibration is produced and input to drive circuit. The drive circuit responds by producing the drive signal in the form of a periodic, pseudosinusoidal staircase function. The staircase function has fundamental frequency f, and has N steps of M discrete nonzero amplitude levels per period. N and M are integers greater than one, with M being less than N. The drive circuit produces the M amplitude levels such that predetermined harmonics of the fundamental frequency f are not present in the drive signal, thereby reducing the possibility of activity dips in the accelerometer output.
59 Citations
16 Claims
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1. An accelerometer for measuring acceleration along a sensitive axis, comprising:
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a support; a proof mass; mounting means for mounting the proof mass to the support such that the proof mass can undergo movement relative to the support along the sensitive axis; and a transducer for reacting to said movement by producing a signal indicative of acceleration along the sensitive axis, the transducer including; (a) a resonator comprising a piezoelectric crystal connected between the proof mass and the support and constructed to undergo mechanical vibration at a frequency f that varies with the force applied to the crystal in response to an electrical drive signal having a harmonic component at frequency f, and means for producing an electrical resonator signal corresponding to said mechanical vibration; and (b) drive circuit means including means for receiving the resonator signal and for producing the drive signal in the form of a periodic pseudosinusoidal staircase function at a fundamental frequency f, the staircase function having N steps and M discrete nonzero amplitude levels per period, M and N being integers greater than 1 with M being less than N, the circuit means including means for producing the M amplitude levels such that predetermined harmonics of the fundamental frequency f are not present in the drive signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An oscillator, comprising:
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a resonator comprising a piezoelectric crystal constructed to undergo mechanical vibration at a frequency f in response to an electrical drive signal having a harmonic component at frequency f, and means for producing an electrical resonator signal corresponding to said mechanical vibration; and drive circuit means including means for receiving the resonator signal and for producing the drive signal in the form of a periodic pseudosinusoidal staircase function at a fundamental frequency f, the staircase function having N steps and M discrete nonzero amplitude levels per period, M and N being integers greater than 1 with M being less than N, the circuit means including means for producing the M amplitude levels such that predetermined harmonics of the fundamental frequency f are not present in the drive signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification