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Method and apparatus for distance measurement

  • US 6,404,703 B1
  • Filed: 07/06/1999
  • Issued: 06/11/2002
  • Est. Priority Date: 05/14/1996
  • Status: Expired due to Fees
First Claim
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1. A distance measuring method comprising the steps of:

  • transmitting between at least one pair of first and second locations a respective first signal having a first propagation speed, wherein the or each said first signal includes a respective first modulation signal having a repetition period longer than a propagation time of said first signal between the at least one pair of the first and second locations, and wherein the or each said first signal is sequentially transmitted at two carrier frequencies, and said carrier frequencies are selected according to the respective first modulating signal;

    transmitting between the or each pair of first and second locations a respective second signal having a second propagation speed higher than the first propagation speed; and

    determining the distance between the first and second locations from the difference in propagation time between said first and second signals.

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