METHOD AND DEVICE FOR RECEIVING A DEGRADED RADIONAVIGATION SIGNAL

• US 20090052505A1
• Filed: 10/11/2005
• Published: 02/26/2009
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: Image Sensing Systems Incorporated (Autoscope Technologies Corp.), MiTAC International Corporation (MiTAC Holdings Corp.)
• Original Assignee: Thales SA
• Inventors: Raffegeau, Jean-Pierre
• Granted Patent: US 7,826,518 B2
• Time in Patent Office: Days
• US Class Current: 375/150
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence

Abstract

The invention relates to a method of receiving a radionavigation signal. Over a first determined time correlations of the sampled signal received are calculated with a locally generated code of period T. The signal is received and the code is shifted with respect to one another from one correlation to the next correlation. Over the determined time, the signal is shifted from one correlation to the next, the code being fixed.

Claims

1. A method of receiving a radionavigation signal comprising the steps of:

over a first determined time, calculating correlations of the sampled signal received with a locally generated code of period T, the first determined time being equal to the period of the code T, the signal received and the code being shifted with respect to one another from one correlation to the next correlation over the determined time, the signal being shifted from one correlation to the next, the code being fixed, the sampled signal comprising a real component I and an imaginary component Q, the samples of the two components I and Q are placed in series alternately in one and the same memory, the calculations of correlation of the code with I and with Q being performed alternately, the results of the correlation calculations for the same component and having the same shift n between the signal and the code, and obtained over Tc code periods, being added together so as to obtain for each component a coherent integration respectively called I_TC(n) and Q_TC(n), I_TC(n)²+Q_TC(n)² being calculated, a sum of the amplitudes or of the powers of the coherent integrations having the same shift n being calculated over a time Tnc (Tnc=K×

Tc) so as to obtain for each shift n a noncoherent integration C(n), prior to the correlation calculations step,

storing the signal in another memory for a second determined time according to a writing frequency fe, the signal being read according to a reading frequency fl such that fl>

fe with a view to the correlation calculations step,

wherein the correlation calculations step is carried out for several codes and in that the signal is read for each code.

3. The method as claimed in claim 1, wherein the second determined time is equal to Tnc.

4. The method as claimed in claim 1, wherein the signal received is a satellite-based and/or pseudolite-based radionavigation signal.

5. A receiver of a radionavigation signal comprising means for implementing the method as claimed in claim 1.

6. The receiver as claimed in claim 5, comprising a correlator able to correlate the signal received with a code, and in that the correlator comprises a nonrotating shift register (2′

) for the code and at least one nonrotating shift register (1 or 1′

) for the signal.

7. The receiver as claimed in claim 6, wherein the nonrotating shift register (2′

) for the code comprises N cells, N being the length of the code, the nonrotating shift register (1′

) for the signal comprises 2N cells and in that it comprises N multipliers each linked on the one hand to a cell of the register (2′

) of the code and on the other hand to a cell of the register (1′

) of the signal and an adder with N inputs, each input being linked to a multiplier.

8. The receiver as claimed in claim 6, wherein, linked to the correlator, means able to store the 2N results arising from the correlator and to increment them respectively in tandem with the results provided by the correlator, for a duration Tc, to carry out 2N coherent integrations.

9. The receiver as claimed in claim 7, wherein, linked to the correlator, means able to store the 2N results arising from the correlator and to increment them respectively in tandem with the results provided by the correlator, for a duration Tc, to carry out 2N coherent integrations.

10. The receiver as claimed in claim 8, wherein it comprises means for obtaining N coherent integration powers or amplitudes.

11. The receiver as claimed in claim 9, wherein it comprises means for obtaining N coherent integration powers or amplitudes.

12. The receiver as claimed in claim 10, wherein it comprises means able to store the N coherent integration powers or amplitudes, and to increment them respectively for a duration Tnc, as and when the coherent integration powers or amplitudes are obtained, to carry out N noncoherent integrations.

13. The receiver as claimed in claim 11, wherein it comprises means able to store the N coherent integration powers or amplitudes, and to increment them respectively for a duration Tnc, as and when the coherent integration powers or the amplitudes are obtained, to carry out N noncoherent integrations.

14. The receiver as claimed in claim 6, wherein it furthermore comprises linked to the correlator another memory able to store the signal received according to a writing frequency fe and to restore it to the correlator according to a reading frequency fl such that fl>

fe.

17. The method as claimed in claim 3, wherein the signal received is a satellite-based and/or pseudolite-based radionavigation signal.

18. The receiver as claimed in claim 7, wherein it furthermore comprises linked to the correlator another memory able to store the signal received according to a writing frequency fe and to restore it to the correlator according to a reading frequency fl such that fl>

fe.

19. The receiver as claimed in claim 8, wherein it furthermore comprises linked to the correlator another memory able to store the signal received according to a writing frequency fe and to restore it to the correlator according to a reading frequency fl such that fl>

fe.

20. The receiver as claimed in claim 9, wherein it furthermore comprises linked to the correlator another memory able to store the signal received according to a writing frequency fe and to restore it to the correlator according to a reading frequency fl such that fl>

fe.

21. The receiver as claimed in claim 10, wherein it furthermore comprises linked to the correlator another memory able to store the signal received according to a writing frequency fe and to restore it to the correlator according to a reading frequency fl such that fl>

fe.

22. The receiver as claimed in claim 11, wherein it furthermore comprises linked to the correlator another memory able to store the signal received according to a writing frequency fe and to restore it to the correlator according to a reading frequency fl such that fl>

fe.

23. The receiver as claimed in claim 12, wherein it furthermore comprises linked to the correlator another memory able to store the signal received according to a writing frequency fe and to restore it to the correlator according to a reading frequency fl such that fl>

fe.

24. The receiver as claimed in claim 13, wherein it furthermore comprises linked to the correlator another memory able to store the signal received according to a writing frequency fe and to restore it to the correlator according to a reading frequency fl such that fl>

fe.

2. The method as claimed in claim 2, wherein the correlation calculations step is carried out for several frequency assumptions considered to compensate for the Doppler effect and in that the signal is read for each of these assumptions.

15. The method as claimed in claim 2, wherein the second determined time is equal to Tnc.

16. The method as claimed in claim 2, wherein the signal received is a satellite-based and/or pseudolite-based radionavigation signal.