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Method for Optimizing an Acquisition of a Spread-Spectrum Signal from a Satellite by a Mobile Receiver

  • US 20110206090A1
  • Filed: 09/25/2009
  • Published: 08/25/2011
  • Est. Priority Date: 09/26/2008
  • Status: Active Grant
First Claim
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1. A method for optimizing an acquisition of a spread-spectrum signal originating from a satellite by a mobile receiver, said method comprising:

  • receiving a signal transmitted by at least one transmitter, the signal being modulated by a pseudo-random code;

    generating a local replica of the pseudo-random code of the signal transmitted;

    transmitting a plurality of assumptions relating to the frequency fi of the signal received at an initial instant t0 and to the trend of this frequency over time up to a final instant tn corresponding to an integration time, each assumption concerning the trend of the frequency of the signal between the initial instant and the final instant being called trend path;

    calculating the correlation functions s(fi, tk, τ

    ) of all the pairs of frequency-time assumptions (fi, tk);

    choosing a first initial frequency assumption f1 corresponding to the initial instant t0;

    acquiring at least one information item concerning the movement of the receiver, and deducing therefrom, for the initial frequency assumption f1, the trend assumptions for the frequency of the signal over time;

    determining the respective total energy, corresponding to the maximum of the correlation function, also called correlation peak, of all the possible trend paths of the frequency of the signal between the instants t0 and tn, the total energy of each possible trend path being obtained by coherently aggregating correlation results between the initial t0 and final tn instants, the frequency taking in succession all the frequency values located on the chosen trend path;

    selecting the trend path whose total energy is the strongest;

    choosing in succession all the other possible initial frequency assumptions and, for each initial frequency assumption, in selecting the trend path of the frequency of the signal whose total energy is the strongest; and

    deciding that, out of all the paths selected on each frequency assumption, the path which has the strongest energy is the most likely path and corresponds to the real path followed by the receiver.

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