| 摘要 |
Disclosed is a unidirectional surface acoustic wave transducer for a SAW transversal filter, which uses a piezoelectric substrate made of Lithium Tetraborate (Li2B4O7) and has a phase difference (Deltatheta) of approximately 45° between a reflection center and an excitation center, thereby improving its filter characteristics. A curve D1 is obtained by plotting plural points using as X and Y values the values of a relative electrode thickness H/lambda(%) and a relative electrode width M/lambda of a point having the maximum reflection coefficient |r|, and then connecting the plural points. A curve D2 is obtained by plotting plural points using as X and Y values the values of a relative electrode thickness H/lambda(%) and a relative electrode width M/lambda of a point of the phase difference (Deltatheta) of 45° between a reflection center and an excitation center, and then connecting the plural points. Therefore, the relative electrode thickness H/lambda(%) and the relative electrode width M/lambda with the excellent filter characteristics are obtained from an intersection point of two curves. Preferably, the values of the relative electrode thickness H/lambda(%) and the relative electrode width M/lambda are in the range of Q shown in FIG. 5.
|
