Continuous integration based satellite navigational signal acquisition
First Claim
1. A method implemented in a global satellite navigation receiver for acquisition of signals received from navigational satellites, the method comprising:
- in a coarse acquisition phase;
for a selected dwell in a list of code-frequency dwells, calculating a non-coherent accumulated power from the signals,if the non-coherent accumulated power is less than a low threshold value then eliminating the selected dwell from the list of code-frequency dwells and continuing the coarse acquisition phase,if the non-coherent accumulated power is greater than a high threshold then initiating a fine acquisition phase using the selected dwell;
if a number of integration intervals for the selected dwell exceeds a predetermined duration then initiating the fine acquisition phase using the list of code-frequency dwellsin the fine acquisition phase;
for a given dwell, calculating a fast Fourier transform of a set of recent signal samples to determine coherent accumulated powers for a set of frequencies, anddiscarding frequencies whose coherent accumulated powers are less than an average power.
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Abstract
A method and device to acquire navigational satellite signals combines non-coherent and coherent integrations and can efficiently acquire both strong and weak signals. Successive steps eliminate lower powered and less likely combinations of code offsets and carrier frequencies or dwells of a given satellite signal. Only remaining dwells then are correlated and integrated over larger time duration to obtain the most probable dwell or dwells, which results in reduced computational load. The selection of most likely dwells is based on Parseval'"'"'s theorem on equivalence of power in time and frequency domains. An optimal estimator algorithm efficiently estimates the probable navigation data bits embedded in the received signal. In case of an ambiguity due to several possible dwells, the steps are repeated with a new set of signal samples.
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Citations
18 Claims
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1. A method implemented in a global satellite navigation receiver for acquisition of signals received from navigational satellites, the method comprising:
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in a coarse acquisition phase; for a selected dwell in a list of code-frequency dwells, calculating a non-coherent accumulated power from the signals, if the non-coherent accumulated power is less than a low threshold value then eliminating the selected dwell from the list of code-frequency dwells and continuing the coarse acquisition phase, if the non-coherent accumulated power is greater than a high threshold then initiating a fine acquisition phase using the selected dwell; if a number of integration intervals for the selected dwell exceeds a predetermined duration then initiating the fine acquisition phase using the list of code-frequency dwells in the fine acquisition phase; for a given dwell, calculating a fast Fourier transform of a set of recent signal samples to determine coherent accumulated powers for a set of frequencies, and discarding frequencies whose coherent accumulated powers are less than an average power. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A global satellite navigation system receiver device comprising an RF front end for receiving signals from navigational satellites, a baseband section receiving IF signals from the RF front end, and a processor receiving I,Q signal samples from the baseband section, wherein the processor implements a two-phase signal acquisition process comprising a coarse acquisition phase and a fine acquisition phase,
wherein the coarse acquisition phase comprises: -
for a selected dwell in a list of code-frequency dwells, calculating a non-coherent accumulated power from the signals, if the non-coherent accumulated power is less than a low threshold value then eliminating the selected dwell from the list of code-frequency dwells and continuing the coarse acquisition phase, if the non-coherent accumulated power is greater than a high threshold then initiating a fine acquisition phase using the selected dwell; if a number of integration intervals for the selected dwell exceeds a predetermined duration then initiating the fine acquisition phase using the list of code-frequency dwells wherein the fine acquisition phase comprises; for a given dwell, calculating a fast Fourier transform of a set of recent signal samples to determine coherent accumulated powers for a set of frequencies, and discarding frequencies whose coherent accumulated powers are less than an average power. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification