| 摘要 |
PURPOSE:To measure the accurate speed of the vehicle by sensing the Doppler frequency of the reflected wave from the vehicle only during a specified time, and receiving the reflected sonic wave from the vehicle passing a specified position. CONSTITUTION:A means which intermittently generates the ultrasonic wave is constituted by an ultrasonic wave transceiver 7, a transmitting driver 12, a reference oscillator 13, and a timing signal generator 14. The reflected wave from the vehicle is inputted to a Doppler signal sensor 16 via the ultrasonic wave transceiver 7 and a received signal selecting amplifier 15. The Doppler signal which is sensed by the Doppler signal sensor 16 is inputted to a speed computing and processing circuit 19 via a Doppler signal selecting filter 17 and a gate switch circuit 18, and the vehicle speed is computed. The filter 17 and the gate switch 18 allow the Doppler frequency in the reflected ultrasonic wave from the vehicle to pass during only the specified time other than the intermittent driving time. |
