| 摘要 |
PURPOSE:To eliminate a noise caused by a multipath reflection, by making a receiving signal branch, giving delay and attenuation, and adding it so as to become antiphase to the receiving signal. CONSTITUTION:A reflected wave which reaches a vibrator of a probe 11 hits against a discontinuous face of acoustic impedance except a target and generates a multipath reflection, therefore, following a reflected wave P0 reflected by the target, reflected waves P1, P2 by the multipath reflection appear. In this case, when an output of a receiving circuit 14 is adjusted suitably by a delaying circuit 22 so that a delayed signal P0' is set so as to appear at the time coinciding with the first multiple reflected wave P1 as shown in B, and also the attenuation quantity of an attenuating circuit 23 is adjusted so that amplitude of the delayed signal P0' is set so as to coincide with amplitude of the first multiple reflected wave P1, an output signal of the attenuating circuit 23 becomes like C. When this output signal is added to negative phase by an adding circuit 15, a desired reflected wave P0 only appears in the output of the adding circuit as shown in D, and unnecessary multiple reflected waves P1, P2... can be eliminated. |
