BOUNDARY ACOUSTIC WAVE FILTER

摘要

A boundary acoustic wave filter which can reduce insertion loss in the pass band. A longitudinal coupling resonator type boundary acoustic wave filter (100) comprises a piezoelectric composed of LiNbO<SUB>3</SUB> using as a major surface a surface obtained by rotating the Y axis through 15°±10°, a dielectric composed of a silicon oxide film and laminated on the piezoelectric, and an electrode structure arranged on the boundary between the piezoelectric and the dielectric, wherein the electrode structure comprises a plurality of IDTs (112-114, 122-124, 132-134, 142-144, 152-154, 162-164), and reflectors (111, 115, 121, 125, 131, 135, 141, 145, 151, 155, 161, 165) arranged along the propagating direction of boundary acoustic wave, and, assuming the intersection width of the electrode finger in the plurality of IDTs is W and the period of the electrode finger is P, the following relation is satisfied; 20=W/P=45.