Step filter for estimating distance in a time-of-flight ranging system

  • US 9,194,943 B2
  • Filed: 04/11/2012
  • Issued: 11/24/2015
  • Est. Priority Date: 04/12/2011
  • Status: Active Grant
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First Claim
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1. A method of estimating a distance between a mobile node and a base station, said method comprising:

  • providing a display on the mobile node;

    providing a time of flight subsystem including circuitry incorporated in the mobile node and the base station and generating a time of flight distance signal by periodically transmitting a time of flight signal between the mobile node and the base station and measuring the time taken for transmission of the time of flight signal therebetween;

    providing an accelerometer on the mobile node and generating an accelerometer signal therewith;

    initializing the value of a distance estimate signal based on the time of flight distance signal;

    detecting a human step based on variances in the accelerometer signal;

    changing the value of the distance estimate signal by a predetermined quantum only upon detection of a human step, wherein the value of the distance estimate signal is increased by the predetermined quantum responsive to the time of flight distance signal being greater than the distance estimate signal and wherein the value is decreased by the predetermined quantum responsive to the time of flight distance signal being less than the distance estimate signal; and

    periodically displaying the value of the distance estimate signal on the display.

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