SATELLITE-BASED POSITIONING SYSTEM IMPROVEMENT
First Claim
1. In an SPS system for identifying the location of a receiver in the presence of satellite signal attenuation having a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data:
- a receiver for detecting, acquiring, and tracking a set of the encoded signals and simultaneously determining the code phases of said set with respect to said epochs;
an aiding source to transmit information to the SPS system, andwherein said receiver is comprised of a processor executing an algorithm for computing an initial approximate location from measured satellite Doppler differences.
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Accused Products
Abstract
A method, device and system for determining a receiver location using weak signal satellite transmissions. The invention involves a sequence of exchanges between an aiding source and a receiver that serve to provide aiding information to the receiver so that the receiver'"'"'s location may be determined in the presence of weak satellite transmissions. With the aiding information, the novel receiver detects, acquires and tracks weak satellite signals and computes position solutions from calculated pseudo ranges despite the inability to extract time synchronization date f, '"'"'n the weak satellite signals. The invention includes as features, methods and apparatus for the calibration of a local oscillator, the cancellation of cross correlations, a Doppler location scheme, an ensemble averaging scheme, the calculation of almanac aiding from a table of orbit coefficients, absolute time determination, and a modified search engine.
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Citations
19 Claims
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1. In an SPS system for identifying the location of a receiver in the presence of satellite signal attenuation having a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data:
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a receiver for detecting, acquiring, and tracking a set of the encoded signals and simultaneously determining the code phases of said set with respect to said epochs; an aiding source to transmit information to the SPS system, and wherein said receiver is comprised of a processor executing an algorithm for computing an initial approximate location from measured satellite Doppler differences. - View Dependent Claims (2, 3)
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4-5. -5. (canceled)
- 6. A method of calibrating a local oscillator of an SPS receiver comprising the steps of counting local oscillator cycles and fractions thereof over a period precisely determined by a number of signal framing intervals, calculating a calibration offset and using the calibration offset to correct the oscillator frequency
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8. An SPS system for identifying the location of a receiver in the presence of satellite signal attenuation comprising:
- a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data;
a receiver for detecting, acquiring, tracking a set of the encoded signals and simultaneously determining the code phases of said set with respect to said epochs;
an aiding source to transmit information to the SPS system, a canceler for reducing the amplitude of strong signals wherein the canceler is integrated into a correlator. - View Dependent Claims (9, 10)
- a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data;
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11-18. -18. (canceled)
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19. An SPS system for identifying the location of a receiver in the presence of satellite signal attenuation comprising:
- a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data;
a receiver for detecting, acquiring, tracking a set of the encoded signals and simultaneously determining the code phases of said set with respect to said epochs; and
a search engine having a search range of at least 60 chips after acquisition of the first satellite.
- a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data;
Specification