Crystal oscillator and method with amplitude and phase control

In an oscillator:

• a crystal element, a charge amplifier connected to the crystal element for providing a voltage corresponding to charge through the crystal element, an integrator for integrating the voltage from the charge amplifier, means connected between the integrator and the crystal element to complete a positive feedback loop in which the crystal element is driven in accordance with the integrated voltage, and means for maintaining the feedback loop at unity gain.

In an oscillator:

• a crystal element, a charge amplifier connected to the crystal element for providing a voltage corresponding to charge through the crystal element, an integrator for integrating the voltage from the charge amplifier, a multiplier connected between the integrator and the crystal element to complete a positive feedback loop in which the crystal element is driven in accordance with the integrated voltage, and means for applying a control signal to the multiplier for combination with the integrated voltage to control the level of the voltage with which the crystal element is driven to maintain the feedback loop at unity gain.

In an oscillator:

• a crystal element, a charge amplifier connected to the crystal element for providing a voltage corresponding to charge through the crystal element, an integrator for integrating the voltage from the charge amplifier, means connected between the integrator and the crystal element to complete a positive feedback loop in which the crystal element is driven in accordance with the integrated voltage, and means for maintaining the feedback loop at unity gain, and a compensation loop for applying a current to the charge amplifier to cancel the effect of shunt capacitance in the crystal element.

In an oscillator:

• a crystal element, a charge amplifier connected to the crystal element for providing a voltage corresponding to charge through the crystal element, an integrator for integrating the voltage from the charge amplifier, means connected between the integrator and the crystal element to complete a positive feedback loop in which the crystal element is driven in accordance with the integrated voltage, and means for maintaining the feedback loop at unity gain, and means connected between the output of the integrator and the input of the charge amplifier for applying a biasing current to the charge amplifier.

In an oscillator:

• a crystal element, a charge amplifier connected to the crystal element for providing a voltage corresponding to charge through the crystal element, an integrator for integrating the voltage from the charge amplifier, a multiplier connected between the integrator and the crystal element for applying a driving voltage to the crystal element in accordance with the voltage from the integrator, and means responsive to the voltage from the charge amplifier for applying a control signal to the multiplier to adjust the level of the driving voltage applied to the crystal element to maintain unity gain around the loop formed by the charge amplifier, the integrator, the multiplier and the crystal element.

In an oscillator:

• a crystal element, a charge amplifier connected to the crystal element for providing a voltage corresponding to charge through the crystal element, an integrator for integrating the voltage from the charge amplifier, a multiplier connected between the integrator and the crystal element for applying a driving voltage to the crystal element in accordance with the voltage from the integrator, means responsive to the voltage from the charge amplifier for applying a control signal to the multiplier to adjust the level of the driving voltage applied to the crystal element to maintain unity gain around the loop formed by the charge amplifier, the integrator, the multiplier and the crystal element, a compensation capacitor connected to the input of the charge amplifier, means for applying tracer signals of opposite phases to the compensation capacitor and the crystal element, means connected to the output of the charge amplifier for providing a control signal corresponding to the net tracer signal passing to the charge amplifier from the crystal element and the compensation capacitor, and means responsive to the control signal for adjusting the level of the tracer signal applied to the compensation capacitor to offset the tracer signal from the crystal element and eliminate the net tracer signal in the charge amplifier.

In an oscillator:

• a frequency determining element, a charge amplifier, and a circuit providing an odd number of integrations connected in a loop to provide an output signal of predetermined frequency.

In a method of generating a signal of predetermined frequency, the steps of:

• exciting a frequency determining element, a charge amplifier and an integrator connected in an oscillator loop to produce an output signal of predetermined frequency, providing a control signal corresponding to the amplitude of the output signal, and adjusting the level of the output signal in accordance with the control signal to maintain the output signal at a substantially constant level.

In a method of generating a signal of predetermined frequency, the steps of:

• exciting a frequency determining element, a charge amplifier and an integrator connected in an oscillation loop to produce an output signal of predetermined frequency, providing a control signal corresponding to the amplitude of the output signal, and multiplying the output signal by the control signal to adjust the level of the output signal in accordance with the control signal and thereby maintain the output signal at a substantially constant level.

In a method of generating a signal of predetermined frequency, the steps of:

• exciting a crystal, a charge amplifier and an integrator connected in an oscillation loop to produce an output signal of predetermined frequency, providing a control signal corresponding to the amplitude of the output signal, and passing signals of substantially equal magnitude and opposite phase through the crystal and a compensating capacitor in parallel with the crystal to cancel the effect of shunt capacitance in the crystal.

In a method of generating a signal of predetermined frequency with a crystal element connected in a positive feedback loop with a charge amplifier and an integrator, the steps of:

• amplifying charge through the crystal element with the charge amplifier to provide a voltage corresponding to said charge, integrating the voltage corresponding to the charge, exciting the crystal element in accordance with the integrated voltage, and maintaining the feedback loop at unity gain.

In a method of generating a signal of predetermined frequency with a crystal element connected in a positive feedback loop with a charge amplifier and an integrator, the steps of:

• amplifying charge through the crystal element with the charge amplifier to provide a voltage corresponding to said charge, integrating the voltage corresponding to the charge, exciting the crystal element in accordance with the integrated voltage, and maintaining the feedback loop at unity gain by multiplying the integrated voltage by a control signal to control the level of the voltage with which the crystal element is excited.

In a method of generating a signal of predetermined frequency with a crystal element connected in a positive feedback loop with a charge amplifier and an integrator, the steps of:

• amplifying charge through the crystal element with the charge amplifier to provide a voltage corresponding to said charge, integrating the voltage corresponding to the charge, exciting the crystal element in accordance with the integrated voltage, and maintaining the feedback loop at unity gain, and applying a current to the charge amplifier to cancel the effect of shunt capacitance in the crystal element.

In a method of generating a signal of predetermined frequency with a crystal element connected in a positive feedback loop with a charge amplifier and an integrator, the steps of:

• amplifying charge through the crystal element with the charge amplifier to provide a voltage corresponding to said charge, integrating the voltage corresponding to the charge, exciting the crystal element in accordance with the integrated voltage, and maintaining the feedback loop at unity gain, and applying to the charge amplifier a biasing current derived from the integrated voltage.

In a method of generating a signal of predetermined frequency with an oscillator having a frequency determining crystal element, a charge amplifier, an integrator, and a multiplier connected in a loop, the steps of:

• amplifying charge through the crystal element in the charge amplifier to provide a voltage corresponding to said charge, integrating the voltage from the charge amplifier, applying the integrated voltage to the multiplier, driving the crystal element with a voltage from the multiplier, and adjusting the gain of the multiplier in response to the voltage from the charge amplifier to adjust the level of the driving voltage applied to the crystal element to maintain unity gain around the loop formed by the charge amplifier, the integrator, the multiplier and the crystal element.

In a method of generating a signal of predetermined frequency with a crystal element, a charge amplifier, and an integrator in an oscillation loop, the steps of:

• amplifying charge from the crystal element with the charge amplifier to provide a voltage corresponding to said charge, integrating the voltage from the charge amplifier in the integrator, applying a driving voltage to the crystal element with a multiplier in accordance with the voltage from the integrator, applying a control signal to the multiplier in accordance with the voltage from the charge amplifier to adjust the level of the driving voltage applied to the crystal element to maintain unity gain around the loop formed by the charge amplifier, the integrator, the multiplier and the crystal element, connecting a compensation capacitor to the input of the charge amplifier, applying tracer signals of opposite phases to the compensation capacitor and the crystal element, monitoring the output of the charge amplifier to provide a control signal corresponding to the net tracer signal passing to the charge amplifier from the crystal element and the compensation capacitor, and for adjusting the level of the tracer signal applied to the compensation capacitor in accordance with the control signal to offset the tracer signal from the crystal element and eliminate the net tracer signal in the charge amplifier.

In a method of generating a signal of predetermined frequency, the steps of connecting a frequency determining element, a charge amplifier, and a circuit providing an odd number of integrations in a loop, and exciting the loop to provide an output signal of predetermined frequency.

In a method of generating a signal of predetermined frequency, the steps of:

• exciting a frequency determining element connected in an oscillator loop to produce an output signal of predetermined frequency, providing a control signal corresponding to the amplitude of the output signal, and linearly multiplying the output signal by the control signal to maintain the amplitude of the output signal at a substantially constant level.

In a method of measuring variations in a physical parameters, the steps of:

• varying the series resonant frequency of a crystal in accordance with the parameter to be measured, exciting the crystal in an oscillator loop to produce an output signal having a frequency corresponding to the parameter to be measured, providing a control signal corresponding to the amplitude of the output signal, and linearly multiplying the output signal by the control signal to maintain the amplitude of the output signal at a substantially constant level.

In a method of compensating for the shunt capacitance of a frequency selective crystal element which is in series with a buffer amplifier in a seriesfeedback oscillator circuit, the steps of:

• applying current from the crystal element to the input of the buffer amplifier to produce an output signal, applying the output signal from the buffer amplifier to a differential amplifier to produce inverted and noninverted signals, applying the noninverted signal to the crystal element as a driving signal, and applying the inverted signal to a compensation capacitor connected to the input of the buffer amplifier to provide a compensation signal which is substantially equal in magnitude and opposite in phase to the signal passing through the shunt capacitance of the crystal element.

In a method of reducing an interfering crosstalk signal coupled from a first crystal oscillator circuit to a second crystal oscillator circuit, the steps of:

• providing a crosstalk cancellation signal from the first crystal oscillator circuit, said crosstalk cancellation signal being oppositely phased with respect to the interfering crosstalk signal, and coupling the crosstalk cancellation signal into the second crystal oscillator circuit to cancel the interfering signal.

In a method for automatic cancelling of a crosstalk interference signal which is generated in a source circuit and coupled through stray coupling impedance to interfere with a crosstalk-sensitive circuit, the steps of:

• injecting a crosstalk tracer signal into the source circuit and into the crosstalk-sensitive circuit, said crosstalk tracer signal having a frequency which does not interfere with operation of the crosstalk-sensitive circuit, obtaining an inverted tracer signal from the source circuit, coupling the inverted tracer signal to the crosstalk-sensitive circuit so that the tracer signal coupled to the crosstalk-sensitive circuit is summed with the inverted tracer signal to provide a residual tracer signal which results from imperfect cancellation of the tracer signal and the inverted tracer signal, monitoring the amplitude of the residual tracer signal to provide a control signal, and adjusting the amplitude of the inverted tracer signal in accordance with the control signal to minimize the amplitude of the residual tracer signal.

In an oscillator:

• a frequency determining element and a circuit providing an even number of integrations connected in a loop to provide an output signal of predetermined frequency, and means for maintaining precise phase control around the loop, said means including means for isolating a phase error producing element at the predetermined frequency.

In an oscillator:

• a frequency determining element, a charge amplifier, and a circuit providing an odd number of integrations connected in a loop to provide an output signal of predetermined frequency, and means for maintaining precise phase relationships around the loop without active phase adjustment.

In an oscillator:

• a frequency determining element and a circuit providing an even number of integrations connected in a loop to provide an output signal of predetermined frequency, said circuit including a feedback circuit having a forward gain path and a feedback gain path with components which are matched to provide substantially identical phase shifts in the two paths.

In an oscillator:

• a frequency determining element and a circuit providing an even number of integrations connected in a loop to provide an output signal of predetermined frequency, said circuit including a circuit having an overall phase shift substantially equal to 0.degree. or 180.degree..

In an oscillator:

• a frequency determining element and a circuit providing an even number of integrations connected in a loop to provide an output signal of predetermined frequency, said circuit including a lead-lag network connected in series with a low pass filter to cancel phase errors at the predetermined frequency.