PURPOSE: To reduce the influence of a high-degree mode and to suppress a spurious wave in the vicinity of a resonance frequency by comprising a interdigital width weighting IDT electrode by multiplying the approximate function cos-1(αX) of lateral 0th-order mode of main resonance by an approximate function cos(βX) of longitudinal 0th-order mode.
CONSTITUTION: This element is a surface wave element constituted in such way that the interdigital width weighting envelope of an IDT electrode 2 is shown in Y=±cos-1(αX).cos(βX) letting the center of the IDT electrode 2 an origin, assuming an X-axis in the propagating direction of a surface wave and a Y-axis in the vertical direction, and in the case of letting the range of the IDT electrode 2 in the X-axial direction as -X0/2≤X≤X0/2 where, 0<α≤π≤/X0 and 0<β≤π/X0 can be satisfied in a surface wave element in which the IDT electrode 2 with interdigital weighted and reflector electrodes 5a, 5b formed before and behind the IDT electrode are formed on a piezoelectric substrate 1.
TADA YUTAKA
KAWAKATSU KOJI
