| 摘要 |
PURPOSE: A method for discriminating environmental noise in ultrasonic distance measurement is provided to increase reliability of position tracking data by preventing an error due to an ultrasonic wave included in environmental noise. CONSTITUTION: An ultrasonic signal is inputted in a plurality of channels(S10). A first reference frequency(F1) is detected from the received signal and an output for a corresponding state is periodically updated(S20). A second reference(F2) signal is detected from the received signal and an output for a corresponding state is periodically updated(S30). An output state of the first reference frequency is compared with an output state of the second reference frequency and a normal signal is determined(S40).
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