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Method and apparatus for geolocating a wireless communications device

  • US 6,891,500 B2
  • Filed: 11/12/2002
  • Issued: 05/10/2005
  • Est. Priority Date: 03/18/2002
  • Status: Active Grant
First Claim
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1. For a transmitting unit transmitting a signal, a method for determining the time difference of arrival of the a signal received at two or more receiving sites, said method comprising:

  • (a) for the signal received at the two or more receiving sites, determining a frequency domain representation of the signal, wherein the frequency domain representation comprises a two dimensional number for each of a plurality of frequencies, wherein the two dimensional number comprises a phase and a magnitude;

    (b) determining the time difference of arrival using the two-dimensional numbers for like-frequency component pairs from at least two frequency domain representations; and

    (c) generating a phase angle versus like-frequency function and determining the time difference of arrival from a slope of the function;

    (d) determining the location of the transmitting unit from the determined time difference of arrival, wherein a y-intercept of the function represents a frequency offset between the signal received by at least two of the plurality of receiving sites; and

    (e) for a plurality of transmitting units, determining the transmitting unit of interest using radio frequency signature parameters including the frequency offset.

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