| 摘要 |
PURPOSE:To surely remove an error due to a directly received pulse by forming a pseudo signal for a directly received ultrasonic pulse to remove the directly received pulse from the received ultrasonic wave signal. CONSTITUTION:A part of a transmission output is applied to a delay circuit 18 and a filter 19 to generate a pseudo signal simulating a directly received pulse from an ultrasonic pulse generator 4 received at an ultrasonic pulse receiver 5. The pseudo signal and the received ultrasonic pulse, passed through a BPF7 and a rectifier circuit 8, etc. are processed in a differential amplifier 20, therefore, the directly received pulse in the received ultrasonic pulse is removed and car periphery is searched by a reflected ultrasonic pulse. Since said configuration removing the directly received pulse without setting a dead zone or the like a distance measurement errors due to the directly received pulse can be surely prevented. |
