| 摘要 |
PURPOSE:To enable to supply maximum power to ultrasonic wave transducer TRD by connecting a series circuit consisting of resistance and inducatance to TRD in parallel and attaching an impedance matching transformer to TRD. CONSTITUTION:In case of ultrasonic wave TRD consisting of electroacoustic transducer element 14 including a macromolecule piezoelectric film, series circuit 13 consisting of inductance L1 and resistance R1 is connected to element 14 in parallel and impedance matching transformer 12 is connected between connector 11 and element 14. When the resistance and capacity of element 14 at the operational center frequency decided by the constitution of element 14 are denoted R and C respectively and then R1 and L1 are selected so as to be R=R1=(L1/C)<1/2>= input impedance, the impedance of load seen from the secondary coil of transformer 12 becomes pure resistance R. If the winding ratio of transformer 12 is decided so as to match the cable connected to connector 11, characteristic impedance including power source and resistance, maximum power can be supplied to TRD from power source and a reflected signal converted electrically with TRD can be transferred without distortion. |
