METHOD AND APPARATUS FOR CALIBRATING A GLOBAL POSITIONING SYSTEM OSCILLATOR

• US 20090153398A1
• Filed: 12/17/2007
• Published: 06/18/2009
• Est. Priority Date: 12/17/2007
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Hani, Mohammad Bani, Bernhardt, Bruce
• Granted Patent: US 7,796,083 B2
• Time in Patent Office: Days
• US Class Current: 342/357.290
• CPC Class Codes: G01S 19/235 Calibration of receiver components

Abstract

A method (200) and apparatus (100) for calibrating a global positioning system oscillator is disclosed. The apparatus may include a global positioning system receiver (120), a temperature compensated oscillator (130) coupled to the global positioning system receiver, a controller (140) coupled to the global positioning system receiver, and an offset module (150) coupled to the controller. The controller can control the operations of the apparatus. The offset module can send a calibration signal to the global positioning system receiver using values corresponding to an oscillator frequency rate of change vs. time.

Claims

1. An apparatus comprising:

a global positioning system receiver;

a temperature compensated oscillator coupled to the global positioning system receiver;

a controller coupled to the global positioning system receiver, the controller configured to control the operations of the apparatus; and

an offset module coupled to the controller, the offset module configured to send a calibration signal to the global positioning system receiver using values corresponding to an oscillator frequency rate of change vs. time.

2. The apparatus according to claim 1, further comprising a memory coupled to the controller, the memory including a reference oscillator initial frequency offset table,

wherein the values are based on data in the reference oscillator initial frequency offset table.

3. The apparatus according to claim 1, further comprising a memory coupled to the controller, the memory including a reference oscillator initial frequency offset table,

wherein data in the reference oscillator initial frequency offset table is calibrated to parameters that affect a frequency rate of change of the temperature compensated oscillator, and

wherein the values are based on data in the reference oscillator initial frequency offset table.

4. The apparatus according to claim 3, wherein data in the reference oscillator initial frequency offset table is further one of calibrated to a type of the temperature compensated oscillator, calibrated by taking into consideration a location of the temperature compensated oscillator in the apparatus, and calibrated to a size of the temperature compensated oscillator.

5. The apparatus according to claim 3, wherein data in the reference oscillator initial frequency offset table is further calibrated by taking into consideration thermal isolation of the temperature compensated oscillator in the apparatus.

6. The apparatus according to claim 1, wherein the values are based on polynomial coefficients that characterize a frequency rate of change against time of the temperature compensated oscillator.

7. The apparatus according to claim 1, wherein the values are based on a linear approximation of the change in a temperature compensated oscillator offset frequency.

8. The apparatus according to claim 1, wherein the offset module further compensates for temperature compensated oscillator frequency drift during startup of the global positioning system receiver.

9. The apparatus according to claim 1, wherein the values are based on pre-measured frequency drift characteristics of the temperature compensated oscillator.

10. The apparatus according to claim 1,

wherein the global positioning system receiver is configured to lock on to satellite, and

wherein the offset module measures an actual frequency of the temperature compensated oscillator against a desired frequency of the temperature compensated oscillator and updates corresponding values based on the difference between the actual frequency and the desired frequency.

11. The apparatus according to claim 1, wherein the offset module provides the global positioning system receiver with an initial frequency offset value prior to satellite signal acquisition.

12. The apparatus according to claim 11, wherein the offset module provides the global positioning system receiver with updated initial frequency offset values until the temperature compensated oscillator settles to a final frequency.

13. A method comprising:

initiating, in a global positioning system receiver, signal acquisition from a global positioning system satellite;

adjusting a signal from a temperature compensated oscillator based on temporally changing compensation values for the temperature compensated oscillator; and

acquiring a signal from the global positioning system satellite based on the adjusted signals of the temperature compensated oscillator.

14. The method according to claim 13, wherein adjusting is performed prior to satellite signal acquisition.

15. The method according to claim 13, further comprising storing data corresponding to the temporally changing compensation values in a reference oscillator initial frequency offset table, wherein the data in the reference oscillator initial frequency offset table is calibrated to parameters that affect a frequency rate of change corresponding to a temperature of the temperature compensated oscillator.

16. The method according to claim 13, wherein the temporally changing compensation values are based on polynomial coefficients that characterize a frequency rate of change against time of the temperature compensated oscillator.

17. The method according to claim 13, wherein the temporally changing compensation values are based on pre-measured frequency drift characteristics of the temperature compensated oscillator.

18. The method according to claim 13, further comprising:

locking on to the global positioning system satellite;

measuring an actual frequency of the temperature compensated oscillator against a desired frequency of the temperature compensated oscillator; and

updating corresponding temporally changing compensation values based on the measurement.

19. The method according to claim 13, wherein adjusting further comprises calibrating the signal from the temperature compensated oscillator until the temperature compensated oscillator settles to a final frequency.

20. An apparatus comprising:

a global positioning system receiver;

a temperature compensated oscillator coupled to the global positioning system receiver;

a controller coupled to the global positioning system receiver, the controller configured to control the operations of the apparatus;

a memory coupled to the controller, the memory including information corresponding to frequency drift characteristics of the temperature compensated oscillator as a function of frequency and time;

an offset module coupled to the controller, the offset module configured to send a calibration signal to the global positioning system receiver using values based on the information corresponding to frequency drift characteristics, where the offset module provides the global positioning system receiver with the calibration signal prior to satellite signal acquisition; and

an interface coupled to the controller, where the interface is configured to output signals corresponding to a position determined by the global positioning system receiver.