Method and apparatus for adjusting reference oscillator frequency in a mobile wireless device
View Patent ↗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.
1. Apparatus within an integrated mobile device comprising:
cell phone circuitry for generating of an oscillator signal and a frequency error signal;
a controller, coupled to the cell phone circuitry, for processing the frequency error signal to produce a frequency control value;
a carrier numerically controlled oscillator, within GPS circuitry, for generating a carrier tuning oscillator signal in response to the oscillator signal and the frequency control value signal; and
a code numerically controlled oscillator, within GPS circuitry, for generating a code timing oscillator signal in response to the oscillator signal and the frequency control value.
2. The apparatus of claim 1 , wherein the cell phone circuitry comprises a voltage controlled crystal oscillator for generating the oscillator signal.
3. The apparatus of claim 1 , wherein the GPS circuitry comprises assisted GPS circuitry.
4. The apparatus of claim 1 , wherein the frequency control value is a digital word.
5. The apparatus of claim 1 , wherein the cell phone circuitry further comprises a digital signal processor for generating the frequency error signal and supplying the frequency error signal to the controller.
6. The apparatus of claim 1 , wherein the cell phone circuitry further comprises a memory for storing frequency control software for adjusting the frequency of the voltage controlled oscillator under the control of the controller.
7. The apparatus of claim 1 , further comprising within the GPS circuitry at least one processing channel coupled to an analog-to-digital converter, wherein the at least one processing channel is adjusted by a tuner under a control of the carrier numerically controlled oscillator.
8. The apparatus of claim 7 , wherein the carrier numerically controlled oscillator provides a reference signal to the tuner.
9. The apparatus of claim 7 , further comprising a decimation circuit for processing an output of the tuner.
10. The apparatus of claim 9 , wherein the code numerically controlled oscillator controls a sampling rate of the decimation circuit.
11. An integrated mobile device comprising:
an oscillator operable to produce a cellular oscillator signal;
at least one numerically controlled oscillator, wherein the at least one numerically controlled oscillator is operable to generate, in response to the cellular oscillator signal and the frequency control value, a signal that is used for processing GPS satellite signals; and
a processor operable to:
produce a frequency error signal to control the oscillator so as to cause the integrated mobile device to operate within cell phone network specifications;
produce a frequency control value;
search for a pilot tone or a carrier signal by tuning a frequency of the oscillator,
fix the frequency of the oscillator when the pilot tone or the carrier signal are not found;
search for the GPS satellite signals; and return to searching for the pilot tone or the carrier signal when the GPS satellite signals are not found.
12. The integrated mobile device of claim 11 , wherein the oscillator is a voltage controlled oscillator.
13. The integrated mobile device of claim 11 , further comprising assisted GPS circuitry.
14. The integrated mobile device of claim 11 , wherein the frequency control value is a digital word.
15. The integrated mobile device of claim 11 , further comprising a memory for storing frequency control software for adjusting the frequency of the voltage controlled oscillator.
16. The integrated mobile device of claim 11 , further comprising, at least one processing channel coupled to an analog-to-digital converter, wherein the at least one processing channel is adjusted by a tuner under a control of the at least one numerically controlled oscillator.
17. The integrated mobile device of claim 16 , wherein the at least one numerically controlled oscillator comprises a carrier numerically controlled oscillator that provides a reference signal to the tuner.
18. The integrated mobile device of claim 17 , further comprising a decimation circuit for processing an output of the tuner.
19. The integrated mobile device of claim 18 , wherein the at least one numerically controlled oscillator comprises a code numerically controlled oscillator that controls a sampling rate of the decimation circuit.
20. A mobile device comprising:
means for producing-a cellular oscillator signal;
means for producing a frequency error signal for controlling the oscillator to operate the mobile device within cell phone network specifications and producing a frequency control value;
means for generating, in response to the cellular oscillator signal and the frequency control value, a signal that is used for processing GPS satellite signals; and
means for searching for a pilot tone or a carrier signal by tuning a frequency of the means for producing the cellular oscillator signal;
means for fixing the frequency of the means for producing the cellular oscillator signal when the pilot tone or the carrier signal are not found;
means for searching for the GPS satellite signals; and
means for returning to searching for the pilot tone or the carrier signal when the GPS satellite signals are not found.