Patent ID: 7683735

Claim:
A balanced acoustic wave filter device comprising: an unbalanced terminal and first and second balanced terminals; a piezoelectric substrate; and first and second acoustic wave filter sections arranged on the piezoelectric substrate, the first and second acoustic wave filter sections each including at least three interdigital transducers defined by longitudinally coupled resonators; wherein the first acoustic wave filter section includes a first interdigital transducer, a second interdigital transducer, and a third interdigital transducer; the second interdigital transducer being connected to the first balanced terminal, and the first and third interdigital transducers being disposed on either side of the second interdigital transducer; the second acoustic wave filter section includes a fourth interdigital transducer, a fifth interdigital transducer, and a sixth interdigital transducer; the fifth interdigital transducer being connected to the second balanced terminal, and the fourth and sixth interdigital transducers being disposed on either side of the fifth interdigital transducer; the first to sixth interdigital transducers are arranged so that an electric signal that flows through the first balanced terminal and an electric signal that flows through the second balanced terminal have phases different by 180 degrees; and the second interdigital transducer of the first acoustic wave filter section and the fifth interdigital transducer of the second acoustic wave filter section each have first and second interdigital transducer bus bar segments divided in the direction of propagation of acoustic waves, the first and second interdigital transducer segments being electrically connected in series with each other.