Method and device for receiving a degraded radionavigation signal

• US 7,826,518 B2
• Filed: 10/11/2005
• Issued: 11/02/2010
• 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: MNI, Inc. (ORBCOMM Incorporated)
• Inventors: Raffegeau, Jean-Pierre
• Primary Examiner(s): Payne, David C
• Assistant Examiner(s): File, Erin M
• Application Number:
  US11/577,322
• Publication Number:
  US 20090052505A1
• Time in Patent Office: 1,848 Days
• Field of Search: 375/140, 375/147, 375/150
• 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 at least one correlation of a sampled signal received with a locally generated code of period T, the first determined time being equal to the period T of the locally generated code, the sampled signal received and the locally generated code being shifted with respect to one another from one correlation to the next correlation over the first determined time, the sampled signal received being shifted from one correlation to the next, the locally generated code being fixed, the sampled signal received comprising a real component I and an imaginary component Q, wherein samples of the two components I and Q are placed in series in an alternated manner in a same memory, the calculations of correlation of the locally generated code with I and with Q being performed alternately, the results of the correlation calculations for the same I and Q component having the same shift n between the sampled signal received and the locally generated code, and the calculation results obtained over Tc code periods;

adding together the results of the correlation calculations for the same I and Q component so as to obtain for each I and Q component a coherent integration respectively called I_TC(n) and Q_TC(n);

calculating I_TC(n)²+Q_TC(n)², 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; and

storing the sampled signal received 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 based on the correlation calculations step,

wherein the correlation calculations step is carried out for several locally generated codes and the sampled signal received is read for each locally generated code.

2. The method of claim 1, wherein the correlation calculations step is carried out for several frequency assumptions considered to compensate for the Doppler effect and the signal is read for each of these assumptions.

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

4. The method of 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 of claim 1.

6. The receiver of claim 5, comprising a correlator able to correlate the signal received with a code, wherein the correlator comprises a first nonrotating shift register (2′

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

) for the signal.

7. The receiver of claim 6, wherein the first nonrotating shift register (2′

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

) for the signal comprises 2N cells, and the receiver comprises N multipliers each linked to a cell of the first nonrotating shift register (2′

) of the code and to a cell of the second nonrotating shift register (1′

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

8. The receiver of claim 6, wherein, linked to the correlator, are means able to store a set of 2N results arising from the correlator and to increment the stored set of 2N results arising from the correlator, for a duration Tc, to carry out 2N coherent integrations.

9. The receiver of claim 7, wherein, linked to the correlator, are 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 of claim 8, further comprising means for obtaining N coherent integration powers or amplitudes.

11. The receiver of claim 9, further comprising means for obtaining N coherent integration powers or amplitudes.

12. The receiver of claim 10, further comprising 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 of claim 11, further comprising 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 of claim 6, further comprising, linked to the correlator, another memory able to store the signal received according to a writing frequency fe and to restore the signal received to the correlator according to a reading frequency fl such that fl>

fe.

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

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

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

18. The receiver of claim 7, further comprising, linked to the correlator, another memory able to store the signal received according to a writing frequency fe and to restore the signal received to the correlator according to a reading frequency fl such that fl>

fe.

19. The receiver of claim 8, further comprising, linked to the correlator, another memory able to store the signal received according to a writing frequency fe and to restore the signal received to the correlator according to a reading frequency fl such that fl>

fe.

20. The receiver of claim 9, further comprising, linked to the correlator, another memory able to store the signal received according to a writing frequency fe and to restore the signal received to the correlator according to a reading frequency fl such that fl>

fe.

21. The receiver of claim 10, further comprising, linked to the correlator, another memory able to store the signal received according to a writing frequency fe and to restore the signal received to the correlator according to a reading frequency fl such that fl>

fe.

22. The receiver of claim 11, further comprising, linked to the correlator, another memory able to store the signal received according to a writing frequency fe and to restore the signal received to the correlator according to a reading frequency fl such that fl>

fe.

23. The receiver of claim 12, further comprising, linked to the correlator, another memory able to store the signal received according to a writing frequency fe and to restore the signal received to the correlator according to a reading frequency fl such that fl>

fe.

24. The receiver of claim 13, further comprising, linked to the correlator, another memory able to store the signal received according to a writing frequency fe and to restore the signal received to the correlator according to a reading frequency fl such that fl>

fe.