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A neutron radiation insensitive crystal oscillator. The device includes two crystals with neutron sensitivity coefficients of opposite sign. The crystals may be connected either in parallel or series relationships. The addition of tuning reactances to the circuit permits control of the circuit's overall resonance.

Inventor: John R. Vig
Original Assignee: The United States of America as represented by the Secretary of the Army
Current U.S. Classification: 331/162
International Classification: H03B 532

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Citations

Cited PatentFiling dateIssue dateOriginal AssigneeTitle
US4575690Mar 25, 1985Mar 11, 1986The United States of America as represented by the Secretary of the ArmyAcceleration insensitive oscillator

Referenced by

Citing PatentFiling dateIssue dateOriginal AssigneeTitle
US5789845Nov 15, 1995Aug 4, 1998Mitsubishi Denki Kabushiki KaishaFilm bulk acoustic wave device
US6653913Apr 5, 2001Nov 25, 2003Koninklijke Philips Electronics N.V.Tunable piezoelectric filter arrangement using a dielectric material with a voltage-dependent dielectric constant
US8188800Nov 5, 2009May 29, 2012Greenray Industries, Inc.Crystal oscillator with reduced acceleration sensitivity

Claims

1. A method of reducing the effects of neutron radiation acting on a crystal resonator which is the primary frequency determining element of a crystal controlled oscillator, comprising the steps of:

determining the value of the neutron sensitivity coefficient for a first crystal;
determining the value of the neutron sensitivity coefficient for a second crystal, said first crystal having a positive neutron sensitivity coefficient and said second crystal having a negative neutron sensitivity coefficient;
electrically coupling said two crystals as a composite crystal resonator to an electrical oscillator circuit; and
coupling electrical reactance means to one of said crystals for cancelling any difference in the resulting neutron sensitivity of said composite crystal.

2. The method as defined by claim 1 wherein said reactance means comprises capacitive reactance means.

3. The method as defined by claim 1 wherein said reactance means comprises inductive reactance means.

4. The method as defined by claim 1 wherein said two crystals are electrically connected in series to said oscillator circuit and wherein said reactance means comprises variable capacitance means coupled in parallel across one of said two crystals.

5. The method as defined by claim 4 wherein said variable capacitance means is coupled across the crystal of said crystals having the greater magnitude of neutron sensitivity coefficient.

6. The method as defined by claim 1 wherein said first and second crystal are connected in parallel to said oscillator circuit.

7. The method as defined by claim 6 and wherein said reactance means is connected in series to one of said crystals.

8. The method as defined by claim 7 wherein said reactance means comprises capacitive reactance means.

9. The method as defined by claim 7 wherein said reactance means comprises inductive reactance means.

10. The method as defined by claim 7 wherein said reactance means comprises variable capacitance means connected in series to the crystal of said two crystals having the larger magnitude of neutron sensitivity coefficient.

11. The method as defined by claim 1 and additionally including the step of coupling electrical reastance means between said composite resonator and said oscillator circuit for adjusting the output frequency of the oscillator circuit.

12. The method as defined by claim 11 wherein said reactance means of the last recited step comprises capacitive reactance means.

13. The method as defined by claim 11 wherein said reactance means of the last recited step comprises inductive reactance means.

14. The method as defined by claim 11 wherein said reactance means coupled between said composite and said oscillator circuit comprises variable capacitance means coupled in series therebetween.

15. The apparatus for reducing the effects of vibration on a piezoelectric crystal resonator constituting the primary frequency determining element of a crystal controlled oscillator, comprising:

an oscillator;
a composite crystal resonator coupled to said oscillator and comprising first and second resonator crystals, each having a neutron sensitivity coefficient of unequal magnitude, said crystals being further positioned such that the neutron sensitivity coefficient of the first crystal is of opposite sign to the neutron sensitivity coefficient and said second crystal whereby the effective neutron sensitivity of the resonant frequency of the composite crystal resonator is substantially reduced; and
electrical reactance meand coupled to at least one of said first and second resonator crystals for cancelling any net neytron sensitivity between said crystals.

16. The apparatus as defined by claim 15 wherein said reactance means comprises capacitive reactance means.

17. The apparatus as defined by claim 15 wherein said reactance means comprises inductive reactance means.

18. The apparatus as defined by claim 15 wherein said first and second resonator crystals are connected in series to said oscillator and wherein said reactance means comprises variable capacitance means coupled in parallel across one of said resonator crystals.

19. The apparatus as defined by claim 18 wherein said variable capacitance means is coupled across the resonator crystal having the greater magnitude of neutron sensitivity coefficient.

20. The apparatus as defined by claim 15 wherein said first and second resonator crystals are connected in parallel to said oscillator and wherein said reactance means comprises variable capacitance means coupled in series to one of said resonator crystals.

21. The apparatus as defined by claim 20 and wherein said variable capacitance means is coupled in series to the resonator crystal having the greater magnirude of neutron sensitivity coefficient.

22. The apparatus as defined by claim 15 and additionally including electrical reactance means coupled between said composite resonator and said oscillator for adjusting the output frequency of said oscillator to a desired value.

23. The apparatus as defined by claim 22 wherein said last recited reactance means comprises capacitive reactance means coupled in series between said composite resonator and said oscillator.

24. The apparatus as defined by claim 22 wherein said last recited reactance means comprises inductive reactance means coupled in series between said composite resonator and said oscillator.

25. The apparatus as defined by claim 22 and wherein said first and second crystals additionally have different capacitance ratios and are connected in series, and wherein said first recited reactance means coupled to one of said resonator crystals comprises variable capacitance means coupled in parallel to said one crystal whereby the parallel connected variable capacitance means is used to produce substantially zero net neutron sensitivity and wherein said last recited reactance means comprises variable capacitance means used as an output frequency tuning capacitor.

26. The apparatus as defined by claim 22 wherein said first and second additionally have different capacitance ratios and are connected in parallel and wherein said first recited reactance means coupled to one of said resonator crystals comprises variable capacitance means coupled in series to said one crystal, whereby the first recited series capacitor means is used to produce substantially zero net neutron sensitivity and wherein said last recited reactance means comprises variable capacitance means used as an output frequency tuning capacitor.

Drawings