Satellite-based positioning system receiver for weak signal operation
AssigneeSigtec Navigation Pty Ltd.
InventorsRoderick C. Bryant, Eamonn P. Glennon, Andrew G. Dempster, Stanley L. Dougan
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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 from the weak satellite signals.
Claims32
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
- an aiding source to transmit an approximate location of the receiver and the position and velocity of a plurality of satellites;
- wherein the receiver determines a precise location using the approximate location, the satellite positions, the code phases and carrier frequency differences.
A method for determining a precise location of a receiver in the presence of attenuated satellite signals carrying synchronization data comprising:
- receiving and storing almanac data for regional satellites in a receiver;
- requesting from an aiding source an approximate location of the receiver;
- sending an approximate location of the receiver from the aiding source in response to a request from the receiver;
- detecting, acquiring and tracking a set of signals from a plurality of satellites by the receiver;
- determining simultaneously in the receiver the code phases from the set of signals and then determining an offset for each code phase with respect to a corresponding reference code phase;
- sending a request including the identities of the plurality of satellites from the receiver to the aiding source;
- returning from the aiding source to the receiver the positions and velocities of each requested satellite;
- and
- determining in the receiver a position solution using the approximate location, almanac data, code phase differences and satellite positions.
A device for use in an SPS system for determining a precise location in the presence of attenuated satellite signals comprising:
- a transmission means for sending requests for its approximate location and satellite positions and velocities to an external aiding source;
- a reception means for receiving the approximate location and satellite positions and velocities from the external aiding source;
- an antenna to receive transmitted satellite signals;
- a circuit to filter and sample the signals received at the antenna;
- a plurality of signal correlators;
- a control circuit, including a processor and memory, that effects signal detection in which stronger encoded signals are acquired before more attenuated signals by successively increasing a correlator output signal integration period and successively reducing an amplitude threshold value,
- wherein said control circuit determines the code phase offsets for a plurality of detected, acquired and tracked satellite signals in the plurality of signal correllators and using said code phase offsets in a determination of a location solution for the device.
Dependencies are inferred from the claim text.