| 摘要 |
PURPOSE:To decrease the number of reflecting grids, by setting the space between the reflecting grids at a specific value and thus lowering no frequency characteristics of the delay time. CONSTITUTION:A pair of reflectors consisting of the input and output converters 2 and 3 comprising the reed screen type electrodes plus the reflecting grids 4-13 are provided on a piezoelectric substrate 1. The grid space xi+1-xi between the i-th and i+1st reflecting grids counted from the input or output converter 2 or 3 is set to be n-fold (n: >=2 integer) of the length of the elastic surface wave reflected from the i-th reflecting grid. Thus the number of the reflecting grids that is expressed by an equation N=f0.DELTAT/2n+1 (f0: central frequency; DELTAT: delay dispersion) can be decreased down to 1/n compared with the conventional case of n=1. |
