Fast Fourier Transform (FFT) inter frequency loss mitigation and Global Positioning System (GPS) receiver including it

• US 7,643,542 B2
• Filed: 01/31/2006
• Issued: 01/05/2010
• Est. Priority Date: 02/04/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Brenner, Joel
• Primary Examiner(s): Torres; Juan A
• Application Number:
  US11/343,444
• Publication Number:
  US 20060251157A1
• Time in Patent Office: 1,435 Days
• Field of Search: 375/150, 375/130
• US Class Current: 375/150
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence

Abstract

Acquisition method for a localization receiver, in particular for a Global Positioning System (GPS) receiver. It involves the calculation of an interpolated Fast Fourier Transform (FFT) spectrum (S′) of correlated signals in which the frequency lines corresponding to half-integer values of the frequency resolution defined by the FFT are obtained by a combination of both amplitude and phase values of the FFT spectrum (S).

Claims

1. A method of using a receiver for acquiring positioning signals of a geographic localization system, comprising the steps of:

obtaining a positioning signal of the geographic localization system containing localization information;

combining the positioning signal with a local pseudorandom code sequence obtaining a correlation signal;

obtaining a first spectrum of frequency of the correlation signal;

obtaining a second spectrum comprising intermediate-frequency data by complex combinations of amplitude and phase values of adjacent bins of the first spectrum; and

searching for peaks in the second spectrum for use in providing pseudo-ranges and fixes in space and time by said receiver.

2. The method of claim 1, wherein said step of obtaining a second spectrum comprises calculating intermediate-frequency data obtained by complex combinations of amplitude and phase values of pairs of adjacent frequency bins of the first spectrum.

3. The method of claim 2, wherein said step of calculating intermediate-frequency data comprises:

a first complex rotation of a first value of the pair according to an angle;

a second complex rotation of the other value of the pair according to said angle in an opposite direction as the first complex rotation; and

a sum of the complex numbers resulting from the first and second complex rotation.

4. The method of claim 2, wherein said step of calculating intermediate-frequency data comprises the evaluation of

5. The method of claim 1, wherein said step of obtaining a second spectrum comprises calculating intermediate-frequency data obtained by complex combinations of amplitude and phase values of groups of more than two adjacent bins of the first spectrum.

6. The method of claim 1, wherein said step of obtaining a first spectrum of frequency involves a Fast Fourier Transform (FFT).

7. The method of claim 6, wherein said step of obtaining a second spectrum comprises rotations, sums and normalizations of complex numbers.

8. The method of claim 6, wherein said step of obtaining a second spectrum comprises only complex sums and complex multiplication by constants.

9. Computer readable medium containing program instructions capable of being loaded in a memory of a digital processor system to execute the method of claim 1.

10. Receiver for a geographic localization system comprising:

means for receiving a signal containing localization information;

means for demodulating the signal;

means for multiplying the signal with a local pseudorandom code sequence obtaining a correlation signal;

means for obtaining a first spectrum of frequency of the correlation signal;

means for obtaining a second spectrum comprising intermediate-frequency data by complex combinations of amplitude and phase values of adjacent bins of the first spectrum; and

means for detecting peaks in the second spectrum.

11. Receiver for a geographic localization system comprising:

means for obtaining a signal containing localization information;

means for multiplying the signal with a local pseudorandom code sequence obtaining a correlation signal;

means for obtaining a first spectrum of frequency of the correlation signal;

means for obtaining a second spectrum comprising intermediate-frequency data by complex combinations of amplitude and phase values of adjacent bins of the first spectrum; and

means for searching peaks in the second spectrum, wherein said interpolating means are adapted for the evaluation of;

12. A machine-readable medium comprising instructions which, when executed by a machine, cause the machine to perform operations, the instructions comprising:

program code for obtaining a signal containing localization information;

program code for combining the signal with a local pseudorandom code sequence obtaining a correlation signal;

program code for obtaining a first spectrum of frequency of the correlation signal;

program code for obtaining a second spectrum comprising intermediate-frequency data by complex combinations of amplitude and phase values of adjacent bins of the first spectrum; and

program code for searching for peaks in the second spectrum.

13. The machine-readable medium of claim 12, wherein said program code for obtaining a second spectrum comprises program code for calculating intermediate-frequency data obtained by complex combinations of amplitude and phase values of pairs of adjacent frequency bins of the first spectrum.

14. The machine-readable medium of claim 13, wherein said program code for calculating intermediate-frequency data comprises:

program code for performing a first complex rotation of a first value of the pair according to an angle;

program code for performing a second complex rotation of the other value of the pair according to said angle in an opposite direction as the first complex rotation; and

program code for performing a sum of the complex numbers resulting from the first and second complex rotation.

15. The machine-readable medium of claim 13, wherein said program code for calculating intermediate-frequency data comprises program code for performing an evaluation of:

16. The machine-readable medium of claim 12, wherein said program code for obtaining a second spectrum comprises program code for calculating intermediate-frequency data obtained by complex combinations of amplitude and phase values of groups of more than two adjacent bins of the first spectrum.

17. The machine-readable medium of claim 12, wherein said program code for obtaining a first spectrum of frequency utilizes a Fast Fourier Transform (FFT).

18. The machine-readable medium of claim 17, wherein said program code for obtaining a second spectrum comprises program code for performing rotations, sums and normalizations of complex numbers.

19. The machine-readable medium of claim 17, wherein said program code for obtaining a second spectrum utilizes only complex multiplication by constants.

20. Receiver for a geographic localization system, comprising:

a receiving section adapted for obtaining a signal containing localization information;

a correlator processor adapted for multiplying the signal with a local pseudorandom code sequence obtaining a correlation signal;

a signal processor adapted for obtaining a first spectrum of frequency of the correlation signal;

said signal processor also being adapted for obtaining a second spectrum comprising intermediate-frequency data by complex combinations of amplitude and phase values of adjacent bins of the first spectrum; and

a peak detection system for searching peaks in the second spectrum.

21. A receiver for a geographic localization system comprising:

a receiving section for obtaining a signal containing localization information; and

at least one processor executing software stored in a memory and being adapted for;

multiplying the signal with a local pseudorandom code sequence obtaining a correlation signal,

obtaining a first spectrum of frequency of the correlation signal,

obtaining a second spectrum comprising intermediate-frequency data by complex combinations of amplitude and phase values by utilizing;