Patent ID: 9154113
Filing Date: 2015-10-06
Classification: H03H

Abstract:
1. A ladder acoustic wave filter device comprising: an input end; an output end; a series arm that electrically connects the input end and the output end; a series arm resonator provided to the series arm and including a series-arm-side IDT electrode; a parallel arm electrically connected between the series arm and a ground potential; and a parallel arm resonator provided to the parallel arm and including a parallel-arm-side IDT electrode; wherein each of the series-arm-side IDT electrode and the parallel-arm-side IDT electrode includes a pair of comb-shaped electrodes that are interposed between each other, the pair of comb-shaped electrodes each including a busbar and a plurality of electrode fingers extending from the busbar; the series-arm-side IDT electrode is apodization weighted, and the busbars of the series-arm-side IDT electrode are configured so that in an acoustic wave propagation direction, a distance between the busbars in an overlap width direction perpendicular to the acoustic wave propagation direction becomes shorter as an overlap width of the electrode fingers becomes smaller; each of the pair of comb-shaped electrodes of the parallel-arm-side IDT electrode further includes a plurality of dummy electrodes that extends from the busbar and are opposed to the electrode fingers of the other comb-shaped electrode in the overlap width direction, and the parallel-arm-side IDT electrode is an IDT electrode in which the overlap width is constant; and a region bounded by a first envelope and a second envelope has a hexagonal shape, the first envelope being an imaginary line formed by connecting tips of the electrode fingers of one of the pair of comb-shaped electrodes of the series-arm-side IDT electrode, the second envelope being an imaginary line formed by connecting tips of the electrode fingers of the other one of the pair of comb-shaped electrodes of the series-arm-side IDT electrode.