Global positioning system tag system

Claim 1

A method for determining at least one of position and velocity of an object using a plurality of GPS signals transmitted by a plurality of GPS sources, said method comprising the steps of: positioning an interrogator remote from the object, the interrogator responsive to the plurality of GPS signals for determining GPS source information and at least one of frequency information and time and code phase information of at least one of the GPS signals; transmitting an RF signal comprising the GPS source information and the at least one of frequency information and time and code phase information of at least one of the GPS signals from the interrogator; positioning a transponder comprising a plurality of correlators on the object, the transponder responsive to the RF signal and the plurality of GPS signals for: tracking one of the plurality of GPS signals in response to the GPS source information and the at least one of frequency information and time and code phase information; and generating a correlation snapshot by obtaining a noncoherent sum of a plurality of integrations using the plurality of correlators spaced one chip apart, determining the approximate signal peak from the noncoherent sum, prepositioning the correlators at a code phase predicted from the signal peak, and performing an integration with one-eighth chip correlator spacing to produce a plurality of correlator sums, the snapshot comprising a sampled coarse acquisition (C/A) code between the one of the plurality of GPS signals and a replica of the one of the plurality of GPS signals generated by the transponder at regular offsets of some fraction of a C/A code chip; transmitting the snapshot to the interrogator; and processing the correlation snapshot to determine at least one of position and velocity of the transponder.

Claim 2

A method for determining at least one of position and velocity of an object using a plurality of GPS signals transmitted by a plurality of GPS sources, said method comprising the steps of: positioning an interrogator remote from the object, the interrogator responsive to the plurality of GPS signals for determining GPS source information and at least one of frequency information and time and code phase information of at least one of the GPS signals; transmitting an RF signal comprising the GPS source information and the at least one of frequency information and time and code phase information of at least one of the GPS signals from the interrogator; positioning a transponder comprising a plurality of correlators on the object, the transponder responsive to the RF signal and the plurality of GPS signals for: tracking one of the plurality of GPS signals in response to the GPS source information and the at least one of frequency information and time and code phase information; and generating a correlation snapshot by obtaining a noncoherent sum of a plurality of integrations using the plurality of correlators spaced one chip apart, determining the approximate signal peak from the noncoherent sum, prepositioning the correlators at a code phase predicted from the signal peak, and performing an integration with one-eighth chip correlator spacing to produce a plurality of correlator sums, the snapshot comprising a sampled coarse acquisition (C/A) code between the one of the plurality of GPS signals and a replica of the one of the plurality of GPS signals generated by the transponder at regular offsets of some fraction of a C/A code chip; transmitting the snapshot to the interrogator; and processing the correlation snapshot to determine at least one of position and velocity of the transponder.