| 摘要 |
PURPOSE:To measure a distance with high accuracy by eliminating an influence of a roundabout wave and a multiple reflection wave, and detecting only a phase difference to a sending wave motion of direct reflection. CONSTITUTION:A reflected wave from an object is received by a receiver 40, amplified by an amplifying circuit 41, and thereafter, inputted to a waveform shaping circuit 42 and a receiving wave strength detecting circuit 60. In the waveform shaping circuit 42, a receiving signal D is converted to a square wave, and inputted to a phase detecting circuit 50 together with an oscillating signal A, by which a phase difference between sending and receiving wave motions is detected. In an operation controlling circuit 70, a distance to an object is derived by using a detected phase difference which is detected by the phase detecting circuit 50 during the time when a receiving wave strength signal E is obtained in the beginning, after a gate signal B has been outputted. In this way, only a phase difference between a sending wave motions of a direct reflected wave can be detected, therefore, a distance can be measured with high accuracy.
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