摘要:
Guard bands which reduce or eliminate force and sensitivity associated with proof mass motion normal to the substrate as a result of voltage transients is disclosed. The guard bands are biased to reduce the coupling ratio to zero and thereby enable starting and improved performance. Various configurations of guard bands may be employed including distinct inner and outer guard bands, distinct inner guard bands only, extended sense electrodes below inner sensing combs with no outer guards, distinct outer guard bands with extended sense electrodes, and sense electrodes extended beneath both drive and sensing combs.
摘要:
A sensor such as a quartz angular rate sensor is operated in a closed-loop mode including feedback of a control signal. The sensor produces a modulated carrier frequency signal. For stable operation of the feedback loop, the control signal is obtained from the modulated carrier frequency signal by complex demodulation of the modulated signal to produce an in-phase demodulated signal and a quadrature-phase demodulated signal, and the in-phase demodulated signal and the quadrature-phase demodulated signal are filtered by a complex equalizing filter to produce an equalized in-phase signal and an equalized quadrature-phase signal. The equalized in-phase signal represents information sensed by the sensor, and phase of a demodulation reference signal is adjusted to minimize appearance of the information in the equalized quadrature-phase signal. The equalized in-phase and quadrature-phase signals are complex modulated at the carrier frequency to produce the control signal. To compensate for variable delay or phase shift through the feedback loop, the phase of the control signal is adjusted by a phase adjustment signal. For equalization of an angular rate signal from a quartz angular rate sensor, the complex filtering includes compensation for peaking at the drive fork resonant frequency, compensation for secondary modes of vibration of the drive fork, and phase lead compensation for a relatively flat frequency response over the bandwidth of the angular rate signal.
摘要:
A micromechanical inertial sensor is provided having a reduced pickoff Q, while maintaining a high motor Q. The micromechanical inertial sensor includes a pair of proof masses and aligned pickoff plates. Each pickoff plate is spaced from the respective proof mass by a gap that varies in response to out-of-plane movement of the proof mass. The micromechanical inertial sensor also includes at least one voltage source for providing charge to the pickoff plates. By measuring the movement of charge in each electrical circuit that includes a pickoff plate as the gap between the pickoff plate and the respective proof mass varies, a measurement of the rotation of the micromechanical inertial sensor about an input axis may be obtained. The micromechanical inertial sensor further includes resistive elements disposed in series between the voltage source and each pickoff plate to increase the pickoff resonance damping of the micromechanical inertial sensor.
摘要:
An improvement in rate-sensing tuning fork design includes a generally planar and H-shaped sensor frame of piezoelectric material. The frame includes a first pair of tines and a second pair of tines joined to an intermediate cross-piece. Connecting means is provided for connecting each of the second pair of tines to the other of said second pair at a location spaced from said intermediate cross-piece. The connecting means is preferably a connecting member formed of piezoelectric material, with the member being generally parallel to the intermediate cross-piece of the H-shaped frame and disposed between the second pair of tines. The connecting means prevents each of the tines of the second pair from vibrating directly toward or away from each other. A preferred method of use of the device is described.
摘要:
To demodulate an analog signal having information modulated by a carrier, the analog signal is chopped by a chopper, the chopped signal is digitized by a sigma-delta analog-to-digital converter to produce a series of digital samples at a sampling frequency, the digital samples are filtered in a digital decimating filter to produce data words, and the data words are modulated by an intermediate frequency signal to produce a detected information signal. The various frequency signals are generated by a phase-lock loop so that the intermediate frequency is the difference between the carrier frequency and the chopping frequency, and both the chopping frequency and the intermediate frequency are sub-multiples of the sampling frequency. Therefore aliases and artifacts caused by the chopper are either cancelled or fall on multiples of the output sampling frequency, and the intermediate frequency signal can be a square wave without generating artifacts that need be removed by filtering of the detected information signal. Preferably the chopper is placed in an analog portion of a feedback loop of the sigma-delta modulator, and an exclusive-OR gate is placed in the digital portion of the feedback loop, so that the gain of the demodulation process becomes independent of the gain of the chopper. The detection process is especially suited for detecting an angular-rate signal from a vibrating quartz angular rate sensor, because the detection process has very high accuracy, resolution, and linearity.