Patent ID: 8456254

Claim:
An acoustic wave filter device having a trap band and a pass band lower than the trap band, the acoustic wave filter device comprising: a plurality of inductors connected in series in a series arm having and connecting an input terminal and an output terminal; and a plurality of first acoustic wave resonators connected between the series arm and a ground potential, the plurality of inductors and the plurality of first acoustic wave resonators being arranged as a plurality of π-type filter circuits in a direction from the input terminal to the output terminal, each of the plurality of π-type filter circuits being composed of at least one of the plurality of inductors and the first acoustic wave resonators connected between the ground potential and respective ends of the at least one of the plurality of inductors, the acoustic wave filter device further comprising a second acoustic wave resonator having an anti-resonance frequency provided in the series arm, wherein in at least one of portions where the plurality of filter circuits are adjacent to each other, the adjacent π-type filter circuits are electrically connected by the second acoustic wave resonator, and wherein the anti-resonance frequency of the second acoustic wave resonator is located in the trap band defined by a resonance frequency of at least one of the plurality of first acoustic wave resonators.