Patent ID: 9712139
Date: 2017-07-18
CPC Classifications: H03H

Claim:
1. An elastic wave filter device comprising: a serial arm connecting an input terminal to an output terminal; a parallel arm connecting the serial arm to a ground potential; and a plurality of elastic wave resonators; wherein at least two of the plurality of elastic wave resonators includes a piezoelectric substrate and an interdigital transducer electrode located on the piezoelectric substrate; the interdigital transducer electrode includes: when a direction perpendicular or substantially perpendicular to an elastic wave propagation direction is taken as a width direction, a dimension of the low acoustic velocity area in the width direction of one of the at least two of the plurality of elastic wave resonators differs from a dimension of the low acoustic velocity area in the width direction of another one of the at least two of the plurality of elastic wave resonators; the first and second busbars respectively include a plurality of cavities arranged in a dispersed manner along the elastic wave propagation direction, an inner side portion relative to the cavities in the width direction of the interdigital transducer electrode is taken as an inner side busbar section, a portion where the plurality of cavities are provided is taken as a central busbar section, and an outer side portion relative to the central busbar section is taken as an outer side busbar section; the inner side busbar section is belt-shaped and extends in the elastic wave propagation direction; and the central busbar section defines the high acoustic velocity area.