New Sd, Inc.

Systron Donner

Gerald R Newell

Pradeep Bhardwaj

Michael W Nootbaar

Richard A Hanson

James R Woodruff

Harold D Morris

Philip D Flanner

Robert C Willson

Crystal oscillator and method which in one embodiment have a crystal element connected in a positive feedback loop with a charge amplifier and an integrator, with the gain of the loop being maintained at a level of unity. Compensation is provided to offset the effects of shunt capacitance in the crystal element, and precise phase control is maintained around the loop. In other embodiments, a crystal element is connected in a series feedback loop with a buffer amplifier, and operation is provided by maintaining the oscillation signal at level at which distortion, clipping, and saturation do not occur. Compensation for shunt capacitance across the crystal element is provided by applying a compensation signal which is equal in amplitude but opposite in phase to the signal passing through the shunt capacitance to the input terminal of the buffer amplifier to cancel the effect of the shunt capacitance. Compensation is also provided to cancel interfering crosstalk signals between oscillators in systems with more than one oscillator.

Crystal oscillator and method with amplitude and phase control

A voltage-to-frequency converter provides an output signal, the frequency of which is proportional to the instantaneous level of a reference-frequency signal, which is proportional to the output signal of a parameter-sensing circuit. An up-down frequency counter counts the output pulses of the voltage-to-frequency converter. An up-down control terminal coupled to the reference-frequency signal switches the counting direction of the up-down counter to demodulate the output signal of the voltage-to-frequency converter and to provide a digital output signal representative of the time integral of the amplitude of the parameter being sensed. An undersired input signal is reduced by subtracting a cancellation signal having the format of the undesired signal from the undesired input signal. The filter includes a subtractor, or difference circuit, the output of which is coupled to a voltage-to-frequency converter. A feedback path is provided between the output terminal of the voltage-to-frequency converter and one input terminal of the difference circuit. The feedback path includes a circuit for selectively converting the frequency output signal representing the undesired input signal to a cancellation signal. The circuit for selectively converting includes a synchronous carrier signal generator and a reversible up-down counter.

Parameter sensing and processing system

A method for post-production reduction of scale factor nonlinearities including testing of an assembled torque coil and magnetic circuit to determine nonlinearities. To reduce the scale factor nonlinearities, the position of a magnetic circuit component which intercepts the magnetic flux passing through a torque coil is changed. The position of the interior surface of a magnetic end cap is changed with respect to the position of the torque coil. The location of the interior surface of the end cap is varied by using an end cap having a plug portion which is selected to have an interior surface at a location which minimizes scale factor nonlinearities. An force-balance accelerometer has an improved magnetic circuit for reducing nonlinear scale factors. The magnetic circuit which provides a return path for magnetic flux from a permanent magnet source includes an end cap having an interior surface which is located at an optimum distance from the torque coil of the accelerometer to minimize scale factor distortion. The end cap includes a plug member having a predetermined reference surface for engagement with a reference surface in the end cap to locate the interior surface of the plug at an optimum position.

Adjustment of scale factor linearity in a servo accelerometer

A differential capacitive pickoff detector circuit for measuring the difference in spacing of a pair of differential pickoff capacitor plates. Current sources are provided for each output terminal of each of the pair of differential capacitors so that for each capacitor output terminal a current signal alternates between a first current level and a second current level at a predetermined carrier clock switching rate. The capacitors are varied to provide DSB-LC voltage signals across each of the capacitors. The average value of each of the alternating voltages and their amplitudes are automatically adjusted to predetermined levels. The two DSB-LC voltage signals are combined to provide a DSB-SC signal. The DSB-SC signal is synchronously demodulated using a quadrature reference carrier clock signal to provide an output baseband signal which represents the difference between the spacing of the first and second differential capacitor plates.

Capacitive position detector

A series-feedback crystal oscillator has a crystal element in series with a buffer amplifier. The oscillator maintains a linear oscillation signal by using an amplitude control circuit to hold the oscillation signal to a certain level at which distortion, clipping, or saturation does not occur. A control signal indicative of the amplitude of the oscillation signal linearly multiplies the oscillation signal to control the amplitude of the oscillation signal. Shunt capacitance across the crystal is compensated for by connecting a compensating capacitor to the same input terminal of the buffer amplifier as is connected the crystal. A compensating signal, which is equal in amplitude but opposite in phase to the signal passing through the shunt capacitance of the crystal is fed to the input terminal of the buffer amplifier to cancel the effect of the shunt capacitance. A noninverted tracer signal is injected in the feedback loop and passes through the shunt capacitance. An inverted tracer signal passes through the compensating capacitor to cancel the noninverted tracer signal through the shunt capacitance and thereby compensate for the shunt capacitance of the crystal. Interfering crosstalk signals from one crystal oscillator circuit which are coupled into a second crystal oscillator circuit are reduced by feeding an oppositely phased interfering signal into the second crystal oscillator circuit.

Linear crystal oscillator with amplitude control and crosstalk

An analog baseband signal modulates a reference-frequency carrier signal to provide a double-sideband, suppressed-carrier DSB-SC signal. The DSB-SC signal is converted in a voltage-to-frequency converter to a series of pulses, which are demodulated to produce a digitally formatted version of the baseband signal. A notch filter for rejecting an undesired analog signal includes a voltage-to-frequency converter and a selective feedback path which demodulates the undesired signal from a frequency-encoded domain back to the analog domain for a cancellation in a summer preceding the voltage-to-frequency converter.

Digital demodulator

A passive mass-spring type of sensing device or other such device for monitoring a particular parameter, for example mechanical vibration, is disclosed herein. This device utilizes an electrically conductive coil having a given impedance disposed within a magnetic field in a way which results in relative movement between the coil and the field corresponding to the particular parameter being monitored, whereby to produce a monitoring signal in the form of a voltage which also corresponds to the parameter being monitored. The device includes a circuit arrangement for electronically damping the relative movement recited above in a substantial way while, at the same time, maintaining the monitoring signal at a measurable value.

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Alamo, CA, United States of America

Gerald R Newell