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Ultrasound intrusion detector

  • US 5,973,996 A
  • Filed: 04/22/1998
  • Issued: 10/26/1999
  • Est. Priority Date: 06/12/1997
  • Status: Expired due to Term
First Claim
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1. A method for detecting the presence of a moving object in a detection area, comprising:

  • emitting a sequence of bursts of ultrasonic energy into the area;

    receiving ultrasonic energy reflected from within the detection area, in response to the sequence of bursts, and generating a sequence of signals respectively responsive thereto;

    comparing each signal in the sequence with a preceding signal, to find a variation in the signals over the sequence of bursts; and

    analyzing the variation in the signals to determine the presence of the moving object,wherein comparing each signal with the preceding signal comprises sampling values of the signals and comparing the sampled values as a function of delay time between emitting the burst and receiving the energy andanalyzing the variation in the signals comprises determining a rate of change of the sampled values compared at a selected delay time.

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