| 摘要 |
PURPOSE:To suppress a shunt of energy of a transmitting pulse to a receiving circuit side, and to secure coupling of a sufficiently tight signal path, by coupling a transducer and a receiving circuit by use of a variable capacity diode. CONSTITUTION:A waveform in case when a pulse generating circuit 1 applies a positive pulse electric signal to a piezoelectric transducer 4 consists of a positive pulse waveform part (a) and a high voltage waveform part (b) of its dynamic current. In case when a transistor 3 is turned on in a moment only and a pulse is applied to the transducer 4, in the waveform part (a) and (b), capacity of a variable capacity diode 5 is reduced, for instance, to several PF or ten and several PF or so in case of 1SV100, and coupling of the transducer 4 and a receiving circuit 6 becomes loose, therefore, it is suppressed sufficiently that energy of a pulse waveform from the pulse generating circuit 1 is shunted to the receiving circuit 6 side. When the transistor 3 is returned to off and a tail part (b) of a high voltage waveform is attenuated gradually, capacity of the variable capacity diode 5 increases, and coupling of the transducer 4 and the receiving circuit 6 becomes tight gradually, therefore, a transfer signal is scarcely attenuated. |
