| 摘要 |
PURPOSE:To make a transmitter large enough to obtain necessary acoustic power and to obtain an excellent signal-to-noise ratio by obtaining a maximum detection output when a signal arrives from a receiver side. CONSTITUTION:A signal wave f2 enters from the side of the receiver 4 and is reflected by the transmitter 3 to cause non-linear interference with an ultrasonic wave f1 from the transmitter, so that it is cought by the receiver 4. The receiver 4 is sufficiently reducible in size and the arrival signal is never masked as a result. A signal arriving from the transmitter side is unnecessary, so the transmitter is made larger enough to generate an ultrasonic wave having a necessary level; and the excellent signal-to-noise ratii is obtained and the minimum frequency of a signal to be detected depends upon the size of the transmitter, so the size should by large enough. |
