| 摘要 |
PURPOSE:To prevent the occurrence of an undesired reflected wave for a surface acoustic wave filter element for multichannel, by short-circuiting both terminals of an unused input transducer. CONSTITUTION:A surface acoustic wave filter device is provided with two input transducers 321 and 322 which are formed interdigitally on a piezoelectric substrate 31 with different frequency bands, an output transducer 33 which is formed interdigitally at a place close to the transducers 321 and 322, and a sound absorber layer 34 provided near the substrate 31. A common terminal 32a of both transducers 321 and 322 is grounded and at the same time connected to the 1st changeover switch 36. Other terminals 32b and 32c are connected to the contacts 36b and 36c of the switch 36, and these contacts serve as the contact of the 2nd changeover switch 37 of an electric signal generator 35. As a result, a reflected wave 38c sent from the transducer 322 is extremely reduced regardless of the presence of a reflected wave 38b given from the transducer 33. |
