Temperature compensated oven controlled crystal oscillator

• US 7,573,345 B2
• Filed: 07/12/2005
• Issued: 08/11/2009
• Est. Priority Date: 07/15/2004
• Status: Active Grant

• Current Assignee: Rakon UK Limited (Rakon Limited)
• Original Assignee: Rakon UK Limited (Rakon Limited)
• Inventors: Ward, Karl Robert, Hardy, Nigel David
• Primary Examiner(s): KINKEAD, ARNOLD M
• Application Number:
  US11/632,239
• Publication Number:
  US 20070268079A1
• Time in Patent Office: 1,491 Days
• Field of Search: 331/176, 331/175, 331/158, 331/116.R, 331/116.FE
• US Class Current: 331/158
• CPC Class Codes: H03L 1/022 by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature H03L1/021 takes precedence
• CPC Class Codes: H03L 1/028 of generators comprising piezoelectric resonators H03L1/021, H03L1/022 take precedence; oscillation generators with a piezoelectric resonator H03B5/32
• CPC Class Codes: H03L 1/04 Constructional details for maintaining temperature constant

Abstract

A method provides a temperature controlled frequency source. The method reduces the effects of temperature variations on an operating frequency of the temperature controlled frequency source by temperature compensating the temperature controlled frequency source. The temperature-controlled frequency source may be an Oven-Controlled crystal oscillator (DCXO) and the temperature-controlled frequency source may be a TCXO ASIC. Analago temperature compensation may be provided by generating zero to fourth-order polynomial Chebyshev functions of temperature.

Claims

1. A method of compensating for temperature-dependent behavior of a tunable circuit, the method comprising:

providing a temperature controlled frequency source, the temperature of which is controlled, in use, such that a variation in temperature of the frequency source is less than a corresponding variation in ambient temperature; and

reducing the effects of variations of an ambient temperature on an operating frequency of the temperature controlled frequency source by compensating the temperature controlled frequency source on the basis of correction data derived during a temperature sweep, said temperature sweep including varying the ambient temperature and activating temperature control of the temperature controlled frequency source.

2. The method of claim 1, wherein the temperature controlled frequency source includes an OCXO.

3. The method of claim 1, wherein the temperature compensation is provided by using a TCXO ASIC.

4. The method of claim 1, wherein the temperature compensation includes fourth-order analog temperature compensation.

5. The method of claim 4, wherein the fourth-order analog temperature compensation is provided by generating zero to fourth-order polynomial Chebyshev functions of temperature.

7. A method according to claim 1, including setting a maximum heater current level for a heater of the temperature controlled frequency source.

8. A method according to claim 1, including monitoring the ambient temperature and selectively operating the temperature controlled frequency source in dependence on the ambient temperature.

9. A method according to claim 8, in which heating of the temperature controlled frequency source is activated in response to the ambient temperature falling below a predetermined value.

10. A method according to claim 9, in which the predetermined value corresponds to a zero temperature coefficient associated with the temperature controlled frequency source.

6. A temperature compensated temperature controlled frequency source comprising:

a temperature controlled frequency source, the temperature of which is controlled such that, in use, a variation in temperature of the frequency source is less than a corresponding variation in ambient temperature; and

temperature compensation circuitry coupled to the temperature controlled frequency source,

wherein the temperature compensation circuitry comprises correction data and is configured to temperature compensate the temperature controlled frequency source for an ambient temperature on the basis of said correction data, the correction data having been derived during a temperature sweep, said temperature sweep including varying the ambient temperature and activating temperature control of the temperature controlled frequency source.

11. A temperature compensated temperature controlled frequency source according to claim 6, wherein the temperature controlled frequency source comprises an OCXO.

12. A temperature compensated temperature controlled frequency source according to claim 6, wherein the temperature compensation circuitry comprises a TCXO ASIC.

13. A method of compensating for temperature-dependent behavior of a tunable circuit, the method comprising:

providing a temperature controlled frequency source; and

reducing the effects of temperature variations on an operating frequency of the temperature controlled frequency source by temperature compensating the temperature controlled frequency source on the basis of temperature correcting data derived during a calibration process, said calibration process including activating temperature control of the temperature controlled frequency source;

wherein heating of the temperature controlled frequency source is activated in response to the ambient temperature falling below a predetermined value; and

wherein the predetermined value corresponds to a substantially zero temperature coefficient associated with the temperature controlled frequency source.

14. The method of claim 13, wherein the temperature controlled frequency source includes an OCXO.

15. The method of claim 13, wherein the temperature compensation is provided by using a TCXO ASIC.

16. The method of claim 13, wherein the temperature compensation includes fourth-order analog temperature compensation.

17. The method of claim 16, wherein the fourth-order analog temperature compensation is provided by generating zero to fourth-order polynomial Chebyshev functions of temperature.