| 摘要 |
PURPOSE:To make it possible to satisfy all conditions a video intermediate-frequency filter requires, by fixing the propagative direction of elastic surface waves within the range between counter clockwise 126 and 132 degrees from the Y axis. CONSTITUTION:On substrate 1 of a X-cut single LiTaO3 crystal, exciting-receiving transducers 2 and 3 for elastic surface waves are arranged which have an angle of theta deg. from the Y axis toward the Z axis, namely, counterclockwise, so that characteristics of electrical-mechanical coupling coefficient K<2> shown in the figure can be obtained. Here, coefficient K<2> should be more than 0.9% in order to maintain the specific band width of a video signal within at 10% while keeping an insertion loss small. In addition, angle theta should also be between 126 and 132 degrees counterclockwise in order to satisfy conditions that a bulk level is less than -40dB, so that conditions can all be satisfied which the video intermediate VIF filter requires. |
