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Position tracking system

  • US 5,163,004 A
  • Filed: 01/11/1991
  • Issued: 11/10/1992
  • Est. Priority Date: 01/11/1991
  • Status: Expired due to Term
First Claim
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1. A position tracking system, comprising:

  • at least three continuous-wave, simultaneously-transmitting radio frequency transmitting stations disposed in spaced relation to each other, one of which stations generating a signal at a first fixed frequency, and the other transmitting stations each generating a signal at a fixed frequency differing therefrom and from each other; and

    a mobile receiving station simultaneously receiving the different frequency signals and responsive thereto to convert each frequency signal differing from said first frequency to said first frequency and simultaneously comparing the phase difference therebetween to produce an output signal indicative of the location of said mobile receiving station relative to the location of said transmitting stations.

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