Frequency plan for GPS receiver

• US 7,197,089 B2
• Filed: 08/30/2002
• Issued: 03/27/2007
• Est. Priority Date: 08/30/2002
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Najarian, Richard
• Primary Examiner(s): Ha; Dac
• Assistant Examiner(s): Joseph; Jaison
• Application Number:
  US10/231,985
• Publication Number:
  US 20040042562A1
• Time in Patent Office: 1,670 Days
• Field of Search: 375/316, 375/134, 375/149, 375/148, 375/150, 342/90, 455/12.1, 455/427, 455/131, 455/313, 455/323, 455/333
• US Class Current: 375/316
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain

Abstract

The present invention provides a GPS receiver having a unique frequency plan, thereby eliminating interference due to internally generated frequencies. In general, the GPS receiver has downconversion circuitry that uses a first synthesizer output signal with a center frequency of 272F to reduce the L1 (308F) or L2 (240F) GPS signal to an intermediate frequency signal. The intermediate frequency signal is then digitized by sampling circuitry wherein the sampling circuitry is driven by a second synthesizer output with a center frequency of 8.5F. The resultant digitized signal contains the GPS information carried in the received GPS signal and has a center frequency of 2F. By selecting 8.5F as the basic reference for all internally generated frequencies, where F is 5.115 MHz, all internally generated frequencies are interrelated by nature and no internal signals in the RF-to-baseband conversion can interfere with the received GPS signal within its information bandwidth.

Claims

1. A GPS receiver comprising:

downconversion ion circuitry adapted to receive a GPS input signal with a center frequency of 308F and a first synthesizer output signal having a center frequency of 272F and provide a downconverted output signal having a center frequency of 36F;

a frequency synthesizer adapted to provide said first synthesizer output signal and a second synthesizer output signal having a center frequency of 8.5F; and

sampling circuitry operatively associated with said down conversion circuitry and adapted to be driven by said second synthesizer output signal and provide a digitized output signal with a center frequency of 2F, wherein said digitized output signal includes GPS information carried in said GPS input signal and F is a reference frequency.

2. The GPS receiver according to claim 1 wherein said GPS input signal is L1.

3. The GPS receiver according to claim 1 wherein F is 5.115 MHz.

4. The GPS receiver according to claim 1 further comprising a reference oscillator adapted to provide a reference signal having a center frequency of 4.25F being operatively connected to said frequency synthesizer.

5. The GPS receiver according to claim 4 wherein said frequency synthesizer comprises a divide-by-thirty-two circuit adapted to divide said first synthesizer output signal to provide said second synthesizer output signal.

6. The GPS receiver according to claim 5 wherein said frequency synthesizer further comprises a frequency and phase detector having first and second inputs and a divide-by-two circuit adapted to divide said second synthesizer output signal to provide a first input signal having a center frequency of 4.25F to said first input and wherein said second input of said frequency and phase detector is operatively connected to said reference oscillator to receive said reference signal.

7. The GPS receiver according to claim 6 wherein said frequency synthesizer further comprises a VCO adapted to provide said first synthesizer output signal in response to an output of said frequency and phase detector.

8. The GPS receiver according to claim 7 wherein said frequency synthesizer further comprises a filter operatively coupling said frequency and phase detector to said VCO and adapted to filter the first synthesizer output signal provided to said VCO.

9. The GPS receiver according to claim 1 wherein said downconversion circuitry comprises a mixer.

10. The GPS receiver according to claim 1 wherein said sampling circuitry comprises an analog-to-digital converter.

11. The GPS receiver according to claim 1 wherein said downconversion circuitry comprises a mixer and said sampling circuitry comprises an analog-to-digital converter.

12. The GPS receiver according to claim 1 further comprising signal processing logic adapted to recover said GPS information from said digitized output signal.

13. The GPS receiver according to claim 1 further comprising filtering circuitry operatively associated between said downconversion circuitry and said sampling circuitry, wherein said filtering circuitry is adapted to remove unwanted frequency components from said down-converted output signal.

14. The GPS receiver according to claim 13 further comprising first gain logic operatively associated between said downconversion circuitry and said filtering circuitry and second gain logic operatively associated between said filtering circuitry and said sampling circuitry, wherein said first gain logic is adapted to amplify said downconverted output signal and provide said filtering circuitry with a signal having sufficient input power and said second gain logic is adapted to provide said sampling circuitry with a filtered signal having sufficient input power.

15. The GPS receiver according to claim 1 wherein said downconversion circuitry, said frequency synthesizer, and said sampling circuitry are integrated onto a single semiconductor die.

16. The GPS receiver according to claim 1 wherein said downconversion circuitry and said sampling circuitry are adapted to receive differential signals.

17. A semiconductor die comprising:

downconversion circuitry adapted to receive a GPS input signal with a center frequency of 308F and a first synthesizer output signal having a center frequency of 272F and provide a down-converted output signal having a center frequency of 36F;

a frequency synthesizer adapted to provide said first synthesizer output signal and a second synthesizer output signal having a center frequency of 8.5F; and

sampling circuitry operatively associated with said downconversion circuitry end adapted to be driven by said second synthesizer output signal and provide a digitized output signal with a center frequency of 2F, wherein said digitized output signal includes GPS information carried in said GPS input signal and F is a reference frequency.

18. The semiconductor die according to claim 17 wherein said GPS input signal is L1.

19. The semiconductor die according to claim 17 wherein F is 5.115 MHz.

20. The semiconductor die according to claim 17 wherein said frequency synthesizer comprises a divide-by-thirty-two circuit adapted to divide said first synthesizer output signal to provide said second synthesizer output signal.

21. The semiconductor die according to claim 20 wherein said frequency synthesizer further comprises a frequency and phase detector having first and second inputs and a divide-by-two circuit adapted to divide said second synthesizer output signal to provide a first input signal having a center frequency of 4.25F to said first input and wherein said second input of said frequency and phase detector is operatively connected to a reference oscillator to receive a reference signal with a center frequency of 4.25F.

22. The semiconductor die according to claim 21 wherein said frequency synthesizer further comprises a VCO adapted to provide said first synthesizer output signal in response to an output of said frequency and phase detector.

23. The semiconductor die according to claim 22 wherein said frequency synthesizer further comprises a filter operatively coupling said frequency and phase detector to said VCO and adapted to filter the first synthesizer output signal provided to said VCO.

24. The semiconductor die according to claim 17 wherein said downconversion circuitry comprises a mixer.

25. The semiconductor die according to claim 17 wherein said sampling circuitry comprises an analog-to-digital converter.

26. The semiconductor die according to claim 17 wherein said downconversion circuitry comprises a mixer and said sampling circuitry comprises an analog-to-digital converter.

27. The semiconductor die according to claim 17 further comprising connections for external filtering circuitry operatively associated between said downconversion circuitry and said sampling circuitry.

28. The semiconductor die according to claim 27 further comprising first gain logic operatively associated between said downconversion circuitry and said connections and second gain logic operatively associated between said connections and said sampling circuitry, wherein said first gain logic is adapted to amplify said downconverted output signal and provide said external filtering circuitry with a signal having sufficient input power and said second gain logic is adapted to provide said sampling circuitry with a filtered signal having sufficient input power.

29. The semiconductor die according to claim 17 wherein said downconversion circuitry and said sampling circuitry are adapted to receive differential signals.

30. A GPS receiver comprising:

downconversion circuitry adapted to receive a GPS input signal with a center frequency of 240F and a first synthesizer output signal having a center frequency of 272F and provide a down-converted output signal having a center frequency of 32F;

a frequency synthesizer adapted to provide said first synthesizer output signal and a second synthesizer output signal having a center frequency of 8.5F; and

sampling circuitry operatively associated with said downconversion circuitry and adapted to be driven by said second synthesizer output signal and provide a digitized output signal with a center frequency of 2F, wherein said digitized output signal includes GPS information carried in said GPS input signal and F is a reference frequency.

31. The GPS receiver according to claim 30 wherein said GPS input signal is L2.

32. The GPS receiver according to claim 30 wherein F is 5.115 MHz.

33. The GPS receiver according to claim 30 further comprising a reference oscillator adapted to provide a reference signal having a center frequency of 4.25F being operatively connected to said frequency synthesizer.

34. The GPS receiver according to claim 33 wherein said frequency synthesizer comprises a divide-by-thirty-two circuit adapted to divide said first synthesizer output signal to provide said second synthesizer output signal.

35. The GPS receiver according to claim 34 wherein said frequency synthesizer further comprises a frequency and phase detector having first and second inputs and a divide-by-two circuit adapted to divide said second synthesizer output signal to provide a first input signal having a center frequency of 4.25F to said first input and wherein said second input of said frequency and phase detector is operatively connected to said reference oscillator to receive said reference signal.