| 摘要 |
PURPOSE:To electrically adjust the optimum gradient angle of a device by utilizing the mode conversion of lambda wave-surface wave. CONSTITUTION:On the surface of a thin piezoelectric substrate 10 having a thickness which is substantially the same or slightly less than the wave length, lambda, of sonic wave, interdigital electrodes 11, 12 for input and for output respectively, and a multistrip coupler 13 are provided. The coupler 13 is formed by arranging plural pieces of conductor in parallel to each other on the surface of the substrate. The electrodes 11, 12 are provided so that their electrode fingers are arranged to be parallel with and opposed to the arrangement of conductor pieces of the coupler 13. On the back of the substrate 10, a flat plate-like electrode is provided so as to oppose to the arrangement of conductor pieces of the coupler 13. By the existence of this electrode 14, the propagation of sonic wave through the substrate is influenced, and this can be solved by reducing the number of conductor pieces on the surface, but the speed of sonic wave is varied, therefore a flat platelike electrode 15 is provided to eliminate such influence. |
