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Ultrasonic ground speedometer utilizing Doppler effect

  • US 5,148,409 A
  • Filed: 09/06/1991
  • Issued: 09/15/1992
  • Est. Priority Date: 04/28/1989
  • Status: Expired due to Fees
First Claim
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1. An ultrasonic ground speedometer utilizing Doppler effect comprising:

  • ultrasonic transmitting means for outputting an ultrasonic wave at a predetermined angle against a road surface,ultrasonic receiving means for receiving a reflected ultrasonic wave caused by reflection of the output ultrasonic wave from the road surface;

    arithmetic means for deriving ground speed from Doppler shift between the frequencies of the output ultrasonic wave from said ultrasonic transmitting means and the reflected ultrasonic wave received by said ultrasonic receiving means;

    means for controlling the output ultrasonic wave frequency to keep the reflected ultrasonic wave frequency represented by the sum of the output ultrasonic wave frequency and the Doppler shift to a constant value in response to change in the ground speed derived by said arithmetic means;

    wherein said ultrasonic receiving means includes a resonance type ultrasonic transducer having a resonance point in the vicinity of said reflected ultrasonic wave frequency, andwherein said ultrasonic transmitting means includes an ultrasonic transducer having a flat/sensitivity ultrasonic transducer having a flat frequency/sensitivity characteristic over a relatively wide frequency range obtained by subtracting and adding the Doppler shift from and to a resonance frequency of said ultrasonic receiving means.

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