PURPOSE: To attenuate the bulk wave up to the level where it does not cause the defect of the frequency characteristic, by mixing high-permittivity substance powder equal to the piezoelectric substrate with the adhesive by which the piezoelectric substrate is caused to adhere onto the stem.
CONSTITUTION: Input electrode 12 and output electrode 13 are formed as prescribed on the surface of piezoelectric substrate 11 consisting of LiTaO3, and the reverse face of substrate 11 is caused to face to stem 14, and substrate 11 is bound to a prescribed position on the surface of stem 14 by adhesion through adhesive 15. In this adhesive powder 16 of LiTaO3 which is the same material as substrate 11 is mixed in volume ratio 1:1. As a result, the acoustic impedance of the adhesive layer can be made equal to that of the substrate approximately, and the bulk wave propagated through the reverse face of the substrate is attenuated up to the level, where it does not cause the defect of the frequency characteristic, when the elastic surface wave filter is operated.
TOKUNAGA SHIZUO
KITA SHIGEYUKI
