Patent ID: 7804384

Claim:
An acoustic wave filter device comprising: a piezoelectric substrate; a first longitudinally coupled resonator type acoustic wave filter which is disposed on the piezoelectric substrate and has a plurality of IDT electrodes and first and second terminals; and a second longitudinally coupled resonator type acoustic wave filter which is disposed on the piezoelectric substrate and has a plurality of IDT electrodes and third and fourth terminals; wherein the acoustic wave filter device has a balanced-to-unbalanced conversion function in which, when identical signals are input to the first terminal and the third terminal, a phase difference between a signal output from the second terminal and a signal output from the fourth terminal is approximately 180 degrees in at least a pass band; the first and third terminals are commonly connected and connected to an unbalanced terminal; and the second and fourth terminals are set as first and second balanced terminals, respectively; a propagation direction of an acoustic wave in the first longitudinally coupled resonator type acoustic wave filter and a propagation direction of an acoustic wave in the second longitudinally coupled resonator type acoustic wave filter are different from each other.