Patent ID: 8222971

Claim:
An acoustic wave filter device comprising: a piezoelectric substrate; and a plurality of acoustic wave filters disposed on the piezoelectric substrate; wherein at least one acoustic wave filter of the plurality of acoustic wave filters is a 5-IDT longitudinally-coupled resonator type acoustic wave filter having a balanced-to-unbalanced transforming function and includes first to fifth IDTs arranged in sequence along an acoustic wave propagation direction, a pair of reflectors disposed at both ends of the first to fifth IDTs in the acoustic wave propagation direction, an unbalanced terminal, and first and second balanced terminals; the third IDT includes first and second divided IDT portions being two portions into which the third IDT is divided in the acoustic wave propagation direction; first ends of the second and fourth IDTs are commonly connected to the unbalanced terminal, and second ends thereof are connected to a ground potential via a first ground terminal; first ends of the first, third, and fifth IDTs are commonly connected to the ground potential via a second ground terminal; a second end of the first IDT and the first divided IDT portion are commonly connected to the first balanced terminal, and a second end of the fifth IDT and the second divided IDT portion are commonly connected to the second balanced terminal; the acoustic wave filter device further comprises: a common connection line arranged to commonly connect the first ends of the first, third, and fifth IDTs; and a ground line having a first end connected to the common connection line and a second end connected to the second ground terminal in order to connect the common connection line to the ground potential; and the common connection line is disposed on the piezoelectric substrate, and a connection point at which the ground line is connected to the common connection line is positioned such that a distance between the connection point and the first balanced terminal and a distance between the connection point and the second balanced terminal are the same or substantially the same.