| 摘要 |
PROBLEM TO BE SOLVED: To obtain the surface acoustic wave resonator with less spurious radiation by apotizing each crossing width of an interdigital electrode so as to maximize the transducing efficiency into its vibration mode with respect to a surface acoustic wave of an optional noted overtone. SOLUTION: An interdigital electrode 2 and grating reflectors 31, 32 made of an Al thin film are formed on the surface of a piezoelectric substrate. The crossing width of the interdigital electrode 2 is apotized symmetrically toward the reflectors 31, 32 at both sides according to a weight function F(x) to maximize a transformation ratio Tr of a fundamental wave mode being a noted overtone mode. That is, the crossing width of the interdigital electrode 2 is apotized along with a shape expressed by the weight function F(x) to maximize a general transformation ratio Tr shown in equation with respect to the noted overtone. In the equation,ϕ(x) is a vibration distribution of a surface acoustic wave in the noted overtone mode in a waveguide path, F(x) is a stimulation energy distribution by the interdigital electrode and x is a position of the waveguide path in the broadwise direction.
|
