US 6,052,036 A · Crystal oscillator with AGC and on-chip tuning

Abstract

A highly stable single chip crystal controlled oscillator with automatic gain control. An amplitude detector monitors the output of a crystal controlled oscillator amplifier and produces a feedback signal proportional to the output signal of the amplifier to ensure oscillation is induced at startup and that the amplitude of oscillation is limited to a preselected value during operation to conserve power consumption by the amplifier. The capacitor tank circuit connected to the input of the amplifier includes a voltage variable capacitor the voltage across which is initially established at manufacture to tune the oscillation frequency to a preselected value. The voltage across the voltage variable capacitor is also adjusted to compensate for temperature variations in the circuit.

Claims22

Dependent claims

A crystal controlled oscillator circuit comprising:

an oscillator amplifier having an input and an output, said input being connected to a crystal resonator for establishing oscillation in a preselected frequency range;
means for rectifying the output signal from said oscillator amplifier;
means for capacitively coupling the output of said oscillator amplifier to said rectifying means;
means for low pass filtering the output signal from said rectifying means to produce a d.c. signal proportional to the amplitude of the output of said oscillator amplifier;
a feedback loop for connecting said d.c. signal from said low pass filtering means back to a current source of said oscillator amplifier to regulate the amplitude level of the oscillator amplifier output to a preselected value and limit power consumption of said oscillator circuit;
and
means for tuning said oscillator amplifier in response to variations in absolute temperature of said oscillator circuit.

4 more elements

A crystal controlled oscillator circuit comprising:

an oscillator amplifier having an input and an output, said input being connected to a crystal resonator for establishing oscillation in a preselected frequency range;
an amplitude detector connected to the output of said oscillator amplifier for detecting the amplitude level of the oscillator amplifier output and producing a d.c. signal proportional to the output amplitude level of said oscillator;
a feedback loop for connecting said d.c. signal from said amplitude detector back to a current source of said oscillator amplifier to regulate the amplitude level of the oscillator amplifier output to a preselected value and limit power consumption of said oscillator circuit;
a resonator tank capacitor circuit connected to the input of said oscillator amplifier and having a select capacitance value to tune the oscillation frequency of said amplifier to a preselected value, said tank capacitor circuit including at least one voltage variable capacitor;
means for establishing an initial voltage value across said voltage variable capacitor to tune said resonator tank capacitor circuit, and therefore said oscillator amplifier, to a preselected frequency of oscillation;
and
means for adding to said initial voltage value a temperature compensation voltage value to also adjust the capacitance value of said voltage variable capacitor in response to temperature variations in the circuitry and retain said oscillation frequency at said preselected value, said temperature compensation voltage adding means comprises a circuit which produces a voltage value which is proportional to the absolute temperature of the circuit.

4 more elements

A crystal controlled oscillator circuit comprising:

an oscillator amplifier having an input and an output, said input being connected to a crystal resonator for establishing oscillation in a preselected frequency range;
an amplitude detector connected to the output of said oscillator amplifier for detecting the amplitude level of the oscillator amplifier output and producing a d.c. signal proportional to the output amplitude level of said oscillator;
a feedback loop for connecting said d.c. signal from said amplitude detector back to a current source of said oscillator amplifier to regulate the amplitude level of the oscillator output to a preselected value and limit power consumption of said oscillator circuit;
a resonator tank capacitor circuit connected to the input of said oscillator amplifier and having a select capacitance value to tune the oscillation frequency of said amplifier to a preselected value, said tank capacitor circuit including at least one voltage variable capacitor;
means for establishing an initial voltage value across said voltage variable capacitor to tune said resonator tank capacitor circuit, and therefore said oscillator amplifier, to a preselected frequency of oscillation;
means for adding to said initial voltage value a temperature compensation voltage value to also adjust the capacitance value of said voltage variable capacitor in response to temperature variations in the oscillator circuit and retain said oscillation frequency at said preselected value;
and
said temperature compensation voltage adding means comprises a circuit which produces a voltage value which is proportional to the absolute temperature of the oscillator circuit, said circuit for providing a voltage value which is proportional to the absolute temperature of the oscillator circuit comprises a stable reference voltage connected to a voltage divider which includes as one element a heavily doped resistor with a negative temperature coefficient.

5 more elements

A crystal controlled oscillator circuit comprising:

an oscillator amplifier having an input and an output, said input being connected to a crystal resonator for establishing oscillation in a preselected frequency range;
an amplitude detector connected to the output of said oscillator amplifier for detecting the amplitude level of the oscillator output and producing a d.c. signal proportional to the output amplitude level of said oscillator;
a feedback loop for connecting said d.c. signal from said amplitude detector back to a current source of said oscillator amplifier to regulate the amplitude level of the oscillator amplifier output to a preselected value and limit power consumption of said oscillator circuit;
a resonator tank capacitor circuit connected to the input of said oscillator amplifier and having a select capacitance value to tune the oscillation frequency of said amplifier to a preselected value, said tank capacitor circuit including at least one voltage variable capacitor;
means for establishing an initial voltage value across said voltage variable capacitor to tune said resonator tank capacitor circuit, and therefore said oscillator amplifier, to a preselected frequency of oscillation;
and
said amplitude detector comprises,
means for rectifying the output signal from said oscillator amplifier;
means for capacitively coupling the output of said oscillator amplifier to said rectifying means;
and
means for low pass filtering the output signal from said rectifying means to produce a signal proportional to the amplitude of the oscillation of said oscillator amplifier;
and
said initial voltage value establishing means comprises,
means for generating a digital number;
means for converting said digital number into an analog current value proportional to the value of said digital number;
means for converting said analog current value into a voltage value proportional to said current value;
and
means for coupling said voltage value to said voltage variable capacitor to establish the capacitance value thereof.

15 more elements

A method of generating an oscillator output signal while controlling the power consumption of the oscillator, said method comprising:

providing an oscillator amplifier having an input and an output, said input being connected to a crystal resonator for establishing oscillation in a preselected frequency range;
connecting an amplitude detector to the output of said oscillator amplifier to detect the amplitude level of the oscillator output and produce a d.c. signal proportional to the output amplitude level of said oscillator;
connecting said d.c. signal from said amplitude detector in a feedback loop back to a current source of said oscillator amplifier to regulate the amplitude level of the oscillator amplifier output to a preselected value and limit power consumption of said oscillator circuit;
connecting a resonator tank capacitor circuit having a select capacitance value to the input of said oscillator amplifier to tune the oscillation frequency of said amplifier to a preselected value, said tank capacitor circuit including at least one voltage variable capacitor;
establishing an initial voltage value across said voltage variable capacitor to tune said resonator tank capacitor circuit, and therefore said oscillator amplifier, to a preselected frequency of oscillation;
and
adding to said initial voltage value a temperature compensation voltage value to also adjust the capacitance value of said voltage variable capacitor in response to temperature variations in the oscillator circuit and retain said oscillation frequency at said preselected value, said step of adding to said initial voltage value further includes:
generating a voltage value which is proportional to the absolute temperature of the oscillator circuit.

5 more elements

A method of generating an oscillator output signal while controlling the power consumption of the oscillator, said method comprising:

providing an oscillator amplifier having an input and an output, said input being connected to a crystal resonator for establishing oscillation in a preselected frequency range;
connecting an amplitude detector to the output of said oscillator amplifier to detect the amplitude level of the oscillator amplifier output and produce a d.c. signal proportional to the output amplitude level of said oscillator;
connecting said d.c. signal from said amplitude detector in a feedback loop back to a current source of said oscillator amplifier to regulate the amplitude level of the oscillator amplifier output to a preselected value and limit power consumption of said oscillator circuit;
connecting a resonator tank capacitor circuit having a select capacitance value to the input of said oscillator amplifier to tune the oscillation frequency of said amplifier to a preselected value, said tank capacitor circuit including at least one voltage variable capacitor;
establishing an initial voltage value across said voltage variable capacitor to tune said resonator tank capacitor circuit, and therefore said oscillator amplifier, to a preselected frequency of oscillation;
said step of connecting an amplitude detector further includes:
rectifying the output signal from said oscillator amplifier;
capacitively coupling the output of said oscillator amplifier to said rectifying means;
and
low pass filtering the output signal from said rectifying means to produce a signal proportional to the amplitude of the oscillation of said oscillator amplifier;
and
said step of establishing an initial voltage value further comprises:
generating a digital number;
converting said digital number into an analog current value proportional to the value of said digital number;
converting said analog current value into a voltage value proportional to said current value;
and
coupling said voltage value to said voltage variable capacitor to establish the capacitance value thereof.

14 more elements

A crystal controlled oscillator circuit comprising:

an oscillator amplifier having an input and an output, said input being connected to a crystal resonator for establishing oscillation in a preselected frequency range;
an amplitude detector connected to the output of said oscillator amplifier for detecting the amplitude level of the oscillator output and producing a d.c. signal proportional to the output amplitude level of said oscillator amplifier;
a feedback loop for connecting said d.c. signal from said amplitude detector back to a current source of said oscillator amplifier to regulate the amplitude level of the oscillator amplifier output to a preselected value and limit power consumption of said oscillator circuit;
a resonator tank capacitor circuit connected to the input of said oscillator amplifier and having a select capacitance value to tune the oscillation frequency of said oscillator amplifier to a preselected value, said resonator tank capacitor circuit including at least one voltage variable capacitor;
and
means for establishing an initial voltage value to be applied across said voltage variable capacitor to tune said resonator tank capacitor circuit, and therefore said oscillator amplifier, to a preselected frequency of oscillation which comprises:
means for tuning said oscillator amplifier in response to production variations while manufacturing said oscillator circuit;
and
means for tuning said oscillator amplifier in response to temperature variations while operating said oscillator circuit.

6 more elements

A crystal controlled oscillator circuit constructed on a single substrate comprising:

an oscillator amplifier having an input and an output, said input being connected to a crystal resonator for establishing oscillation in a preselected frequency range;
an amplitude detector connected to the output of said oscillator amplifier for detecting the amplitude level of the oscillator output and producing a d.c. signal proportional to the output amplitude level of said oscillator amplifier;
a feedback loop for connecting said d.c. signal from said amplitude detector back to a current source of said oscillator amplifier to regulate the amplitude level of the oscillator amplifier output to a preselected value and limit power consumption of said oscillator circuit;
a resonator tank capacitor circuit connected to the input of said oscillator amplifier and having a select capacitance value to tune the oscillation frequency of said oscillator amplifier to a preselected value, said resonator tank capacitor circuit including at least one voltage variable capacitor;
and
means for establishing an initial voltage value to be applied across said voltage variable capacitor to tune said resonator tank capacitor circuit, and therefore said oscillator amplifier, to a preselected frequency of oscillation which comprises:
means for tuning said oscillator amplifier in response to production variations while manufacturing said oscillator circuit;
and
means for tuning said oscillator amplifier in response to temperature variations while operating said oscillator circuit.

6 more elements

A method for generating an oscillator signal, comprising:

providing an oscillator amplifier having an input and an output, said input being connected to a crystal resonator for establishing oscillation in a preselected frequency range;
connecting an amplitude detector to the output of said oscillator amplifier to detect the amplitude level of the oscillator output and produce a d.c. signal proportional to the output amplitude level of said oscillator amplifier;
connecting said d.c. signal from said amplitude detector in a feedback loop back to a current source of said oscillator amplifier to regulate the amplitude level of the oscillator amplifier output to a preselected value and limit power consumption of said oscillator circuit;
connecting a resonator tank capacitor circuit to the input of said oscillator amplifier and having a select capacitance value to tune the oscillation frequency of said oscillator amplifier to a preselected value, said tank capacitor circuit including at least one voltage variable capacitor;
and
establishing an initial voltage value to be applied across said voltage variable capacitor to tune said resonator tank capacitor circuit, and therefore said oscillator amplifier, to a preselected frequency of oscillation in accordance with the following steps:
tuning said oscillator amplifier in response to production variations while manufacturing said oscillator circuit;
and
tuning said oscillator amplifier in response to temperature variations while operating said oscillator circuit.

6 more elements

Dependencies are inferred from the claim text.

Crystal oscillator with AGC and on-chip tuning

Life of this patent

Crystal oscillator with AGC and on-chip tuning

Life of this patent

Abstract

Claims22