| 摘要 |
PURPOSE:To attain miniaturization, by constituting the length of a path on which ultrasonic waves are propagated as the sum of the length of the paths where a bulk wave is propagated in a delay medium and a surface acoustic wave is propagated on the side of the delay medium. CONSTITUTION:In applying a high frequency electric signal to a piezoelectric element 5, the piezoelectric element 5 is vibrated mechanically to generate an ultrasonic wave signal in the delay medum. This ultrasonic wave is propagated in the medium 7, reaches a piezoelectric element 6, which is excited mechanically by the ultrasonic wave. An electric signal generated with the vibration of the element 6 is applied to a comb type electrode 10. This electric signal generates a surface wave on a piezoelectric thin film 8 at the side surface of the medium 7 and the surface wave is propagated on the film 8. The surface wave propagating on the film 8 reaches a comb type filter 11 while being reflected at a reflecting grating 12. The surface wave reaching the electrode 11 is converted again into an electric signal and extracted. Through the constitution like this, the delay time is doubled. That is, the size of the delay medium required to obtain a prescribed delay time is halved and the miniaturization of the ultrasonic wave delay line is attained. |
