Method and system for sharing a clock reference signal within an integrated mobile device
View Patent ↗A method and system of a GPS system controlling a voltage of an input signal to an oscillator, the oscillator producing a clock reference signal to the GPS system and a modem system, such that a frequency of the clock reference signal is altered to synchronize the modem system with a corresponding network while the GPS system remains in a locked state.
1. A method of sharing a clock reference signal of an oscillator that is input to a global positioning system (GPS) and a modem system within an integrated mobile device, the method comprising:
receiving an input signal at the modem system;
comparing the input signal with the clock reference signal at the modem system to define a frequency error signal;
altering a signal input at the oscillator by the GPS based upon the frequency error signal from the modem system to alter a frequency of the clock reference signal to synchronize the modem system with a corresponding network; and
altering a value to be added to the altered frequency clock reference signal that is employed by the GPS, wherein the value is based on the frequency error signal.
2. A method as recited in claim 1 , further comprising communicating the frequency error signal to the GPS from the modem system.
3. A method as recited in claim 1 , wherein the corresponding network is selected from a group of networks comprising 2G, 3G, 4G, WiMax, or long term evolution (LTE).
4. A method as recited in claim 1 , further comprising measuring the frequency of the clock reference signal prior to and subsequent to altering the voltage of the signal input at the oscillator to define a difference and correlating a value of the frequency error signal to the difference.
5. A method as recited in claim 1 , wherein the locked state of the GPS has a tolerance in a range of 10 ppb to 100 ppb.
6. A system comprising:
an oscillator to generate a clock reference signal;
a modem system comprising:
a radio frequency (RF) processor to receive the clock reference signal;
an antenna to receive an input signal; and
a digital signal processor (DSP) configured to compare the input signal received by the antenna with the clock reference signal to define a frequency error signal; and
a global positioning system (GPS) comprising:
a GPS radio frequency (RF) processor to receive the clock reference signal;
a frequency compensation unit to receive the frequency error signal and alter a signal input to the oscillator based upon the frequency error signal from the modem system to alter a frequency of the clock reference signal to synchronize the modem system with a corresponding network; and
a carrier numerically controlled oscillator in communication with the frequency compensation unit to add a value to the altered frequency clock reference signal that is employed by the GPS, wherein the value is based on the frequency error signal.
7. A system as recited in claim 6 , wherein the oscillator is a temperature-compensated voltage controlled crystal oscillator.
8. A system as recited in claim 6 , wherein the oscillator is a digital controlled crystal oscillator.
9. A system as recited in claim 6 , wherein the modem system further comprises an automatic frequency control (AFC) unit to produce a digital value that represent a magnitude of the frequency error signal.
10. A system as recited in claim 6 , wherein the GPS further comprises a digital to analog converter (DAC) to convert a digital output of the frequency compensation unit to an analog signal to input to the oscillator.
11. A system as recited in claim 10 , wherein the GPS RF processor comprises the DAC.
12. A system as recited in claim 6 , wherein the GPS further comprises an antenna to receive an additional input signal.
13. A method of sharing a clock reference signal of an oscillator that is input to a global positioning system (GPS) and a modem system, both within an integrated mobile device, the method comprising:
receiving an input signal by the modem system;
comparing the input signal with the clock reference signal by the modem system, defining a frequency error signal; converting the frequency error signal to a digital value;
communicating the frequency error signal to the GPS;
altering a signal input to the oscillator by the GPS via a digital to analog convertor (DAC) based upon the frequency error signal from the modem system to alter a frequency of the clock reference signal to synchronize the modem system with a corresponding network;
converting the clock reference signal to a digital value; and
adding a value to the altered frequency clock reference signal that is employed by the GPS, wherein the value is based on the frequency error signal.
14. A method as recited in claim 13 , wherein synchronizing the modem system further comprises the corresponding network being selected from a group of networks comprising 2G, 3G, 4G, WiMax, or long term evolution (LTE).
15. A method as recited in claim 13 , further comprising measuring the frequency of the clock reference signal prior to and subsequent to altering the voltage of the signal input to the oscillator to define a difference and correlating a value of the frequency error signal to the difference.
16. A mobile device comprising:
a modem system comprising a digital signal processor (DSP) configured to compare an input signal received by the modem system with a clock reference signal generated by a single oscillator to define a frequency error signal; and
a global positioning system (GPS) comprising a frequency compensation unit to receive the frequency error signal and alter a signal input to the single oscillator based upon the frequency error signal from the modem system to alter a frequency of the clock reference signal to synchronize the modem system with a corresponding network, the single oscillator being shared between the modem system and the GPS and being controlled by the GPS, and wherein the GPS is configured to alter a value to be added to the altered frequency clock reference signal that is employed by the GPS, wherein the value is based on the frequency error signal.
17. A system as recited in claim 16 , wherein the GPS comprises a carrier numerically controlled oscillator in communication with the frequency compensation unit to add a value stored therein with the clock reference signal such that the GPS remains in a locked state.
18. A system as recited in claim 16 , wherein the modem system further comprises an automatic frequency control (AFC) unit to produce a digital value that represents a magnitude of the frequency error signal.
19. A system as recited in claim 16 , wherein the GPS further comprises a digital to analog converter (DAC) to convert a digital output of the frequency compensation unit to an analog signal to input to the single oscillator.