RF integrated circuit for downconverting a GPS signal

• US 6,356,602 B1
• Filed: 05/04/1998
• Issued: 03/12/2002
• Est. Priority Date: 05/04/1998
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Rodal, Eric B., Parker, Reed A., Wagner, Gary L., Lau, Chung Y.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US09/073,207
• Time in Patent Office: 1,408 Days
• Field of Search: 375/347, 375/151, 375/344, 375/316, 342/357, 455/183.1, 455/164.1, 455/173.1, 455/192.2, 455/182.2, 455/182.1, 455/333, 455/456, 333/227-233, 333/13, 333/197
• US Class Current: 375/344
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: H03B 2201/0208 the means being an element with a variable capacitance, e.g. capacitance diode
• CPC Class Codes: H03B 5/1209 the amplifier having two current paths operating in a differential manner and a current source or degeneration circuit in common to both paths, e.g. a long-tailed pair. H03B5/1215 takes precedence
• CPC Class Codes: H03B 5/1231 the amplifier comprising one or more bipolar transistors
• CPC Class Codes: H03B 5/124 the means comprising a voltage dependent capacitance
• CPC Class Codes: H03D 7/163 the local oscillations of at least two of the frequency changers being derived from a single oscillator
• CPC Class Codes: H03J 1/0041 for frequency synthesis with counters or frequency dividers
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits

Abstract

A GPS receiver and an RF GPS integrated circuit for receiving a GPS signal. The GPS integrated circuit includes a synthesizer for generating LO signals, first and second downconverters for using the LO signals for downconverting the GPS signal, and a sampler for providing in-phase and quadrature phase sampled output signals representative of the GPS signal. The synthesizer includes a multi-mode divider for providing substantially the same first LO frequency at about the midpoint of the L1 and L2 GPS lo frequencies for either of two reference frequencies. The RF GPS integrated circuit uses an entirely on-chip voltage controlled oscillator (VCO) having a resonator for generating the LO signals and an entirely on-chip filter for filtering a first intermediate frequency signal.

Claims

1. Radio frequency circuitry for downconverting a global positioning system (GPS) satellite signal, comprising:

a synthesizer for providing a first local oscillator (LO) signal, the synthesizer including an amplifier/oscillator for selecting a reference signal by (i) receiving and amplifying a first reference signal having a first reference frequency from an external reference oscillator or (ii) using a resonator for generating a second reference signal having a second reference frequency not equal to said first reference frequency, and a loop for deriving said first LO signal from said selected reference signal; and

a first downconverter for using said first LO signal for downconverting said GPS signal to a first intermediate frequency (IF) signal.

2. The circuitry of claim 1, wherein:

the first downconverter includes a first IF filter for filtering said first IF signal and providing a filtered first IF signal.

3. The circuitry of claim 2, wherein:

the synthesizer is further for generating a complex second LO signal having in-phase (I) and quadrature phase (Q) components at a sub-multiple frequency of said first LO signal; and

further including;

a second downconverter for using said complex second LO signal for downconverting said filtered first IF signal to a complex second IF signal having in-phase (I) and quadrature phase (Q) components.

4. The circuitry of claim 3, further including:

a sampler for sampling said complex second IF signal and providing sampled in-phase (I) and quadrature phase (Q) output signals representative of said GPS signal.

5. The circuitry of claim 1, wherein:

said GPS signal is either one of an L1 GPS signal or an L2 GPS signal; and

said first LO signal has a frequency approximately the midpoint of a carrier frequency of said L1 and said L2 GPS signal.

6. The circuitry of claim 1, wherein:

the circuitry is disposed entirely within a single integrated circuit.

7. The circuitry of claim 1, wherein:

said loop includes a phase detector coupled to said amplifier/oscillator for receiving said selected reference signal and providing an error signal corresponding to a phase difference between said selected reference signal and a feedback signal;

a local oscillator for providing said first LO signal having a first LO frequency controlled by said error signal; and

a multi-mode divider for dividing said first LO frequency by a selected one of a first divide number for providing said feedback signal having said first reference frequency or a second divide number for providing said feedback signal having said second reference frequency.

8. A method of downconverting a global positioning system (GPS) satellite signal, comprising steps of:

selecting a reference signal by (i) receiving and amplifying a first reference signal having a first reference frequency from an external reference oscillator or (ii) using a resonator for generating a second reference signal having a second reference frequency not equal to said first reference frequency;

deriving a first LO signal from said selected reference signal; and

using said first LO signal for downconverting said GPS signal and providing a first intermediate frequency (IF) signal.

9. The method of claim 8, further comprising a step of:

filtering said first IF signal for providing a filtered first IF signal.

10. The method of claim 8, further including steps of;

generating a complex second LO signal having in-phase (I) and quadrature phase (Q) components at a sub-multiple frequency of said first LO signal; and

using said complex second LO signal for downconverting said filtered first IF signal to a complex second IF signal having in-phase (I) and quadrature phase (Q) components.

11. The method of claim 10, further including:

sampling said complex second IF signal for issuing sampled in-phase (I) and quadrature phase (Q) output signals having information representative of information carried on said GPS signal.

12. The method of claim 8, wherein:

said GPS signal is either one of an L1 GPS signal or an L2 GPS signal; and

said first LO signal has a frequency approximately the midpoint of a carrier frequency of said L1 and said L2 GPS signal.

13. The method of claim 8, wherein:

the step of deriving said first LO signal from said selected reference signal includes steps of;

comparing a phase of said selected reference signal to a feedback signal for providing an error signal;

using said error signal for controlling a first LO frequency of said first LO signal; and

frequency dividing said first LO signal by a selected one of a first divide number for providing said feedback signal having said first reference frequency or a second divide number for providing said feedback signal having said second reference frequency.

14. Radio frequency circuitry for downconverting a global positioning system (GPS) satellite signal, comprising:

a synthesizer including a voltage controlled oscillator (VCO) including a tunable resonator for providing a first local oscillator (LO) signal; and

a first downconverter for using said first LO signal for downconverting said GPS signal to a first intermediate frequency (IF) signal, wherein;

said tunable resonator includes a transformer for providing an oscillation feedback signal and resonating with tuned capacitors at a desired frequency of said first LO signal.

15. The circuitry of claim 14, wherein:

said GPS signal is either one of an L1 GPS signal or an L2 GPS signal; and

said first LO signal has a frequency approximately the midpoint of a carrier frequency of said L1 and said L2 GPS signal.

16. The circuit 14 of claim 14, wherein:

the synthesizer includes an amplifier/oscillator for selecting a reference signal by (i) receiving and amplifying a first reference signal having a first reference frequency from an external reference oscillator or (ii) using a resonator for generating a second reference signal having a second reference frequency not equal to said first reference frequency;

a phase detector coupled to the amplifier/oscillator for receiving said selected reference signal and providing an error signal corresponding to a phase difference between said selected reference signal and a feedback signal;

a local oscillator for providing said first LO signal having a first LO frequency controlled by said error signal; and

a multi-mode divider for dividing said first LO frequency by a selected one of a first divide number for providing said feedback signal having said first reference frequency or a second divide number for providing said feedback signal having said second reference frequency.

17. The circuitry of claim 16, wherein:

at least one of said first divide number and said second divide number is a ratio having an integer numerator and an integer denominator, said denominator greater than one.

18. The circuitry of claim 17, wherein:

said multi-mode divider is further for providing said feedback signal having said first reference frequency by alternately dividing said feedback signal by a divide number A_N and a divide number B_N in repeating sequences, each of said sequences beginning in said divide number A_N and ending in said divide number A_N for providing said feedback signal having said first reference frequency.

19. The circuitry of claim 18, wherein:

at least one of said first divide number and said second divide number is said divide number B_N.

20. The circuitry of claim 14, wherein:

said transformer includes a first horizontal helix and a second horizontal helix disposed one over the other on respective metalization layers of an integrated circuit.

21. The circuitry of claim 14, wherein:

the circuitry is disposed entirely within a single integrated circuit.

22. A method of downconverting a global positioning system (GPS) satellite signal, comprising steps of:

generating a first local oscillator (LO) signal with a voltage controlled oscillator (VCO), said VCO having a tunable resonator; and

using said first LO signal for downconverting said GPS signal and providing a first intermediate frequency (IF) signal, wherein;

the step of generating said first LO signal includes steps of;

coupling an oscillation feedback signal with a transformer; and

tuning capacitors for providing said oscillation feedback signal by resonating with said transformer at a desired frequency of said first LO signal.

23. The method of claim 22, wherein:

said GPS signal is either one of an L1 GPS signal or an L2 GPS signal; and

said first LO signal has a frequency approximately the midpoint of a carrier frequency of said L1 and said L2 GPS signal.

24. The method of claim 22, wherein:

the step of generating said first LO signal includes steps of;

selecting a reference signal by (i) receiving and amplifying a first reference signal having a first reference frequency from an external reference oscillator or (ii) using a resonator for generating a second reference signal having a second reference frequency not equal to said first reference frequency;

comparing a phase of said selected reference signal to a feedback signal for providing an error signal;

using said error signal for controlling a first LO frequency of said first LO signal; and

frequency dividing said first LO signal by a selected one of a first divide number for providing said feedback signal having said first reference frequency or a second divide number for providing said feedback signal having said second reference frequency.

25. The method of claim 24, wherein:

at least one of said first divide number and said divide number is a ratio having an integer numerator and an integer denominator, said denominator greater than one.

26. The method of claim 25, wherein:

the step of dividing said first LO frequency by said first divide number includes steps of alternately dividing by a divide number A_N and a divide number B_N in a sequence, said sequence beginning in said divide number A_N and ending in said divide number A_N; and

continuously repeating said sequence for providing said feedback signal having said first reference frequency.

27. The method of claim 26, wherein:

at least one of said first divide number and said second divide number is said number B_N.

28. The method of claim 22, wherein:

said transformer includes a first horizontal helix and a second horizontal helix disposed one over the other on respective metalization layers of an integrated circuit.

29. A global positioning system (GPS) receiver, comprising:

a radio frequency (RF) GPS section including a synthesizer including a voltage controlled oscillator (VCO) including a tunable resonator for providing a first local oscillator (LO) signal and a complex second LO signal at a sub-multiple of said first LO signal;

a first downconverter for using said first Lo signal for downconverting said RF signal and providing a first intermediate frequency (IF) signal, said first downconverter including a filter for filtering said first IF signal;

a second downconverter for using said second LO signal for downconverting said filtered first IF signal and providing a complex second IF signal; and

a sampler for sampling said second IF signal and providing sampled in-phase (I) and quadrature phase (Q) output signals having information representative of information carried on said RF signal;

a microprocessor system for computing navigational information from GPS correlations; and

a GPS digital signal processing (DSP) section coupled to the RF GPS IC for cooperating with the microprocessor system for synchronizing to said sampled I and Q output signals and providing said GPS correlations.

30. The GPS receiver of claim 29, wherein:

said RF signal is either one of an L1 GPS signal or an L2 GPS signal; and

said first LO signal has a frequency approximately the midpoint of a carrier frequency of said L1 and said L2 GPS signals.

31. The GPS receiver of claim 29, wherein:

said synthesizer includes an amplifier/oscillator for selecting a reference signal by (i) receiving and amplifying a first reference signal having a first reference frequency from an external reference oscillator or (ii) using a resonator for generating a second reference signal having a second reference frequency not equal to said first reference frequency;

a phase detector coupled to the amplifier/oscillator for receiving said selected reference signal and providing an error signal for a phase comparison of said selected reference signal to a feedback signal;

the VCO for receiving said error signal and providing said first LO signal; and

a multi-mode divider for frequency dividing said second LO signal by a selected one of a first divide number for providing said feedback signal having said first reference frequency or a second divide number for providing said feedback signal having said second reference frequency.

32. The receiver of claim 29, wherein:

the RF GPS section is disposed entirely in a single integrated circuit.