Patent ID: 8354897

Claim:
An elastic wave filter comprising: a piezoelectric substrate; and a longitudinally coupled resonator-type elastic wave filter unit provided on the piezoelectric substrate; wherein the longitudinally coupled resonator-type elastic wave filter unit comprises first to fifth IDTs arranged in an elastic wave propagation direction and first and second reflectors arranged in the elastic wave propagation direction so as to be disposed on either side of an area in which the first to fifth IDTs are disposed; the third IDT comprises first and second divided comb-shaped electrodes arranged in the elastic wave propagation direction, the first divided comb-shaped electrode is disposed at a side near the second IDT, and the second divided comb-shaped electrode is disposed at a side near the fourth IDT, the second and fourth IDTs are connected to an unbalanced signal terminal, the first IDT and the first divided comb-shaped electrode of the third IDT are connected to a first balanced signal terminal, and the fifth IDT and the second divided comb-shaped electrode of the third IDT are connected to a second balanced signal terminal; each of the first and fifth IDTs has a constant electrode finger pitch, and the electrode finger pitch of the first IDT is less than the electrode finger pitch of the fifth IDT; and a signal passing through the first IDT and a signal passing through the second IDT are in phase in an area in which the first and second IDTs are adjacent to each other.