| 摘要 |
PURPOSE:To minimize the frequency dispersion for the propagatin velocity of the elastic wave by using the X-cut lithium tantalate (LiTaO3) of the excellent temperature characteristics for the substrate and then selecting properly the film thickness of the electrode material Al. CONSTITUTION:In the case of the comb-line filter, for instance, the X-cut LiTaO3 is used for substrate 21, and roller-screen type electrodes 23-25 are formed with Al on the surface of the substrate via the normal photolithography method. The film thickness of the Al is set so that product of film thickness h of Al and frequency k of the elastic surface wave may be within 0.01-0.2 or 0.8-1.9. Elastic surface wave 22 is propagated preferably in the direction featuring angles 100 deg.- 150 deg. from the Y axis, and 112 deg. is given to the filter shown in the figure. |
