Method and apparatus for adjusting reference oscillator frequency in a mobile wireless device

• US 7,155,183 B2
• Filed: 01/16/2003
• Issued: 12/26/2006
• Est. Priority Date: 01/16/2003
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Global Locate Incorporated (Broadcom, Inc.)
• Inventors: Abraham, Charles
• Primary Examiner(s): Eng, George
• Assistant Examiner(s): DOAN, PHUOC HUU
• Application Number:
  US10/345,604
• Publication Number:
  US 20040142701A1
• Time in Patent Office: 1,440 Days
• Field of Search: 455/422.1, 455/456.1, 455/351, 455/192.1, 455/196.1, 375/261, 375/350, 342/357.03, 701/213
• US Class Current: 455/192.1
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: H03J 2200/11 Cellular receiver, e.g. GSM, combined with a GPS receiver
• CPC Class Codes: H03J 7/04 where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant
• CPC Class Codes: H04B 1/3805 with built-in auxiliary receivers
• CPC Class Codes: H04B 1/403 using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency

Abstract

A method and apparatus for using a conventional oscillator in a cellular telephone transceiver as a source of a reference signal for a GPS receiver. In one embodiment, the method comprises using a voltage-controlled oscillator (“VCXO”) within a cellular telephone transceiver to generate a reference frequency signal for the GPS receiver. Circuitry within the telephone transceiver generates a frequency error signal. Both of these signals are coupled to GPS circuitry and used to control a carrier numerically controlled oscillator (“NCO”) and a code NCO. The NCOs produce a tuning signal and a timing signal, respectively. The GPS circuitry uses the NCO generated signals to process GPS signals.

Claims

1. Within a mobile device comprising cell phone circuitry and GPS circuitry, a method for producing a reference signal for a GPS receiver comprising:

producing a cellular oscillator signal and a frequency error signal within the cell phone circuitry, where the frequency error signal is for controlling an oscillator to operate the cell phone circuitry within cell phone network specifications;

coupling the oscillator signal to at least one numerically controlled oscillator within GPS circuitry;

processing the frequency error signal to produce a frequency control value that is coupled to the at least one numerically controlled oscillator;

generating, within the at least one numerically controlled oscillator, a signal in response to the cellular oscillator signal and the frequency control value that is used for processing GPS satellite signals;

searching for a pilot tone or a carrier signal of a cellular telephone by tuning a frequency of an oscillatory signal generator;

fixing the frequency of the oscillatory signal generator when the pilot tone or the carrier signal are not found;

searching for the GPS satellite signals; and

returning to searching for a pilot tone or a carrier signal when the GPS satellite signals are not found.

2. The method of claim 1 wherein, the frequency error signal is maintained by the cell phone circuitry within the cell phone transmission specifications.

3. The method of claim 1 wherein, the frequency error signal represents the frequency difference between the pilot tone or the carrier signal and a signal derived from the cellular oscillator signal.

4. The method of claim 1 wherein, the frequency control value is a digital word.

5. The method of claim 1 wherein, the at least one numerically controlled oscillator comprises:

a carrier numerically controlled oscillator for generating a carrier tuning signal; and

a code numerically controlled oscillator for generating a code timing signal.

6. The method of claim 5 wherein, the carrier tuning signal substantially reduces frequency error caused by Doppler shift.

7. The method of claim 1, wherein searching for a pilot tone or carrier signal occurs for a first predetermined time;

fixing the frequency occurs when the first predetermined time lapses;

searching for the GPS satellite signals occurs for a second predetermined time; and

returning to searching for a pilot tone or carrier signal occurs after the second predetermined time lapses.

8. The method of claim 7, wherein the first predetermined time is in a range of about 20 to 30 seconds.

9. The method of claim 7, wherein the second predetermined time is in a range of about 20 to 30 seconds.

10. The method of claim 1, further comprising:

fixing the oscillatory signal generator to the frequency corresponding to the pilot tone or the carrier signal; and

using a voltage-controlled oscillator to adjust the frequency of the oscillatory signal generator to track the pilot tone or the carrier signal.

11. The method of claim 10, further comprising:

establishing a frequency threshold for the frequency of the oscillatory signal generator.

12. The method of claim 11, further comprising:

adjusting the frequency of the oscillatory signal generator towards a center frequency of the cellular oscillator signal in response to the frequency error signal exceeding the frequency threshold.

13. The method of claim 10, further comprising:

adjusting the frequency of the oscillatory signal generator towards a center frequency of the cellular oscillator signal.

14. The method of claim 10, further comprising:

adjusting the frequency of the oscillatory signal generator towards another frequency other than a center frequency of the cellular oscillator signal.

15. The method of claim 10, further comprising:

adjusting the frequency of the oscillatory signal generator to operate the cell phone circuitry within cell phone network specifications.

16. The method of claim 1, further comprising:

providing the signal from the at least one numerically controlled oscillator to at least one tuner to generate a carrier tuning signal.

17. The method of claim 16, further comprising:

using at least one decimation circuit to sample at a sampling frequency the carrier tuning signal generated by the at least one tuner.

18. The method of claim 17, further comprising:

using at least one code numerically controlled oscillator to control the sampling frequency of the at least one decimation circuit.

19. The method of claim 17, further comprising:

coupling the sampled carrier tuning signal to at least one correlator.