BOUNDARY ACOUSTIC WAVE FILTER

摘要

A boundary acoustic wave filter in which out-of-band attenuation can be enlarged. The boundary acoustic wave filter, wherein, on a piezoelectric substrate (101), a dielectric film (102) is formed, at least one longitudinal coupling resonator type boundary acoustic wave filter (110) having a plurality of IDTs on the boundary between the both and at least two single terminal pair boundary acoustic wave resonators (120, 130) are provided, at least one boundary acoustic wave resonator (120) is connected in series with the longitudinal coupling resonator type boundary acoustic wave filter (110), at least one remaining single terminal pair boundary acoustic wave resonator (130) is connected in parallel with the longitudinal coupling resonator type boundary acoustic wave filter (110), antiresonance frequency of a series connection boundary acoustic wave resonator is located on the high frequency side of the pass band of the boundary acoustic wave filter, and the resonance frequency of a parallel connection boundary acoustic wave resonator is located higher than the antiresonance frequency of the series connection boundary acoustic wave resonator.