Personal communications device with GPS receiver and common clock source

• US 6,650,879 B1
• Filed: 04/18/2000
• Issued: 11/18/2003
• Est. Priority Date: 04/18/2000
• Status: Expired due to Term

• Current Assignee: CSR Limited (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Underbrink, Paul A.
• Primary Examiner(s): Nguyen, Lee
• Assistant Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US09/551,060
• Time in Patent Office: 1,309 Days
• Field of Search: 455/456, 455/11.1, 455/13.2, 455/13.3, 455/60, 455/69, 455/76, 455/88, 455/550, 455/552, 455/553, 455/95, 455/86, 455/258, 455/259, 455/260, 455/263, 455/264, 455/188.1, 455/265, 455/255, 455/190.1, 455/192.2, 342/357.02, 342/357.05, 342/357.01, 342/357.12, 701/213, 701/214
• US Class Current: 455/255
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: H03L 7/081 provided with an additional controlled phase shifter H03L7/0998 takes precedence
• CPC Class Codes: H03L 7/1976 using a phase accumulator for controlling the counter or frequency divider

Abstract

The invention is directed to a personal telecommunications device having both global positioning systems (GPS) and telecommunications provisions which share a common clock source. GPS provisions include a feedback loop for controlling an oscillator that generates a GPS system signal based upon the common clock signal. The feedback loop includes a frequency synthesizer for generating a feedback control signal, a phase comparator for generating a control signal in accordance with the feedback signal and the common clock signal, and a loop filter for processing and outputting the control signal to the oscillator to control the frequency of GPS system signals.

Claims

1. A personal communications device comprising:

a telecommunications unit comprising a code division multiple access (CDMA) device, wherein the telecommunications unit further comprises a clock source; and

a global positioning system (GPS) receiver, wherein the GPS receiver comprises a voltage controlled oscillator for generating a GPS system clock signal based upon the clock source, and a feedback loon for controlling the voltage controlled oscillator, wherein the feedback loon comprises,

a phase comparator for generating a control signal in accordance with the feedback signal and the clock source; and

a loop filter for processing the control signal and outputting the control signal to the voltage controlled oscillator.

2. The personal communications device of claim 1 wherein the clock source provides a common clock signal to the global positioning receiver and the telecommunications unit.

3. The personal communications device of claim 1 wherein the clock source comprises a crystal oscillator.

4. The personal communications device of claim 1 wherein the frequency synthesizer comprises:

a controlled oscillator having a variable output controlled by an input signal;

a frequency divider coupled to receive the output of the controlled oscillator and responsive to the output to provide a frequency divided output signal;

a phase compensation circuit coupled to receive the frequency divided output signal from the frequency divider, the phase compensation circuit responsive to the frequency divided output signal to provide an output which compensates for phase lag of the frequency divided output of the frequency divider; and

a phase detector coupled to receive an output of the phase compensation circuit and the GPS system clock signal and to output a signal proportional to difference in phase between the output of the phase compensation circuit and the GPS system clock signal to control the controlled oscillator.

5. The personal communications device of claim 1 wherein the divider is a fractional-N divider.

6. The personal communications device of claim 1 wherein the controlled oscillator is a voltage controlled oscillator.

7. The personal communications device of claim 1 further comprising a switch for selectable engaging the feedback loop to control the voltage controlled oscillator.

8. The personal communications device of claim 1 wherein the switch is permanently set during manufacture.

9. A method of clocking GPS receiver operations comprising the steps of:

receiving a clock signal from a clock source;

generating a control voltage for controlling frequency of an oscillator signal generated by a voltage controlled oscillator based upon a feedback signal generated by a frequency synthesizer; and

generating a system clock signal of a particular frequency in response to the control voltage, wherein the frequency synthesizer generating the feedback signal includes,

receiving the system clock signal;

frequency dividing the system clock signal by at least two integer values to generate a fractional-N divider signal over a discrete time period;

generating a variably delayed signal based upon the fractional-N divided signal within the discrete time period; and

comparing a phase of the variably delayed signal and a reference signal and varying the system clock signal according to a detected phase difference.

10. A method of clocking GPS receiver operations according to claim 9, wherein the clock source comprises a crystal oscillator of a telecommunications unit.

11. A method of clocking GPS receiver operations according to claim 9, wherein the telecommunications unit comprises a CDMA based telecommunications unit.

14. A personal communications device according to claim 9 wherein the means for receiving a telecommunications signal includes the means for generating a clock source signal, and wherein the means for generating a clock source signal comprises a crystal oscillator.

12. A personal communications device comprising:

means for receiving a telecommunications signal;

means for receiving a global positioning system (GPS) signal comprising an oscillator for generating a GPS system clock signal and a feedback loop for generating and providing a control signal to the oscillator; and

means for generating a clock source signal to be provided to the means for receiving a global positioning system (GPS) signal and the means for receiving a telecommunications signal, wherein the feedback loop comprises,

a frequency synthesizer for generating a feedback signal; and

a phase comparator for generating a control signal in accordance with the feedback signal and the clock source signal.

13. A personal communications device according to claim 12 wherein the means for receiving a telecommunications signal comprises a code division multiple access (CDMA) based radio frequency receiver.