Patent ID: 6665332
Filing Date: 2003-12-16
Classification: G01S,H04B

Abstract:
A geolocation system for providing geolocation of a mobile transceiver capable of spread spectrum coded radio frequency emissions and communication, said geolocation system comprising:a plurality of base stations comprising a primary base station and one or more secondary base stations for receiving the spread spectrum coded radio frequency emissions, the primary base station being in communication with the mobile transceiver and the secondary base stations for conveying selected coded information bits from the mobile transceiver to the secondary base stations via the primary base station; means for synchronizing the plurality of base stations to the mobile transceiver in time; means for determining the geolocation of the mobile transceiver based on times of arrival of the spread spectrum coded radio frequency emissions at the plurality of base stations; wherein each of the plurality of base stations comprises: means for identifying a signal of interest in a spread spectrum coded radio frequency emission received at the base station, a portion of the signal of interest including the selected coded information bits conveyed from the mobile transceiver to the secondary base stations via the primary base station; means for determining a time of arrival of the spread spectrum coded radio frequency emission received at the base station; and wherein said means for determining the time of arrival of the spread spectrum coded radio frequency emission received at the one or more secondary base stations comprises: means for dividing the spread spectrum coded radio frequency emission received at the one or more secondary base stations into a plurality of stages as a function of an estimated propagation distance; despreader/demodulator means for despreading/demodulating each of the plurality of stages into the selected coded information bits; and calculating means for calculating the fast Fourier transform of each of the plurality of stages to produce a time-frequency cross ambiguity function to filter and isolate strongest peak.