Thermally locked oven controlled crystal oscillator
AssigneeGreenray Industries, Inc.
InventorSteven J. Fry
Life of this patent
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Abstract
Systems and processes disclosed herein determine the temperature of a crystal, such as a crystal that may be used in a crystal oscillator, using the reference crystal itself. The system can measure the temperature of the crystal without a temperature sensor. Further, a single oven technique may be used to maintain the temperature of the reference crystal. Thus, in certain embodiments, a more compact crystal oscillator can be generated compared to conventional techniques. Further, by measuring the reference crystal based on signals generated by the reference crystal itself, the system disclosed herein is more accurate than many previous crystal oscillator systems.
Claims22
A thermally locked crystal oscillator comprising:
- a reference crystal configured to generate a reference signal in response to an applied voltage;
- a first oscillator circuit configured to obtain a first signal comprising a third overtone frequency of the reference signal;
- a second oscillator circuit configured to obtain a second signal comprising a fundamental frequency of the reference signal;
- a beat frequency generator configured to generate a beat frequency signal for the reference signal based at least in part on the first signal and the second signal;
- a first divider configured to divide the first signal by a first factor to obtain a first modified signal;
- a second divider configured to divide the beat frequency signal by a second factor to obtain a modified beat frequency signal, wherein the first factor and the second factor differ, and the first modified signal and the modified beat frequency signal comprise the same frequency at a specific temperature;
- a phase detector configured to determine a phase difference between the first modified signal and the modified beat frequency signal;
- and
- a heat controller circuit configured to control a heater based at least in part on the phase difference.
A method of generating a precision crystal oscillator signal, the method comprising:
- generating a reference signal from a reference crystal;
- obtaining an overtone signal corresponding to a third overtone of the reference signal;
- obtaining a fundamental signal corresponding to a fundamental frequency of the reference signal;
- generating a beat frequency signal based at least in part on the fundamental signal and the overtone signal;
- converting the overtone signal based on a first factor to a modified overtone signal;
- converting the beat frequency signal based on a second factor to a modified beat frequency signal;
- determining a phase difference between the modified overtone signal and the modified beat frequency signal;
- and
- controlling an oven based at least in part on the phase difference, the oven configured to apply heat to the reference crystal, wherein the reference crystal generates reference signals of different frequencies based at least in part on the temperature of the reference crystal.
Dependencies are inferred from the claim text.