| 摘要 |
PURPOSE:To mask a sneak wave by outputting only a reflected signal by the output voltage of a waveform shaping circuit provided with a waveform shaping circuit and a voltage comparing circuit. CONSTITUTION:An ultrasonic pulse having certain period of a timing circuit 1 is impressed to a transmitter 3 to transmit, and the mixed signal of a reflected signal 16 of a detection object 15 and a sneak wave 17 is received by a receiver 6. The pulse having a certain period of the circuit 1 is supplied to a waveform shaping circuit 5 through a timer circuit 4, and a reference voltage which changes exponential-functionally with time is inputted to a voltage comparing circuit 9. The reflected signal 16 including the sneak wave 17 attained by the receiver 6 is inputted to the circuit 9 through an amplifeir 7 and a detector 8. The output voltage of the circuit 5 and the reflected signal 16 including the sneak wave 17 are compared with each other in the circuit 9 to output only the reflected signal 16. Thus, the sneak wave 17 is masked to detect easily the position of the object 15. |
