Patent ID: 9722576
Date: 2017-08-01
CPC Classifications: H03H

Claim:
1. An elastic wave filter comprising: an unbalanced signal terminal, a first balanced signal terminal, and a second balanced signal terminal; a pair of grating reflectors; first, second, third, fourth, and fifth interdigital transducer (IDT) electrodes arranged in ordinal order between the pair of grating reflectors and each having a wiring electrode and a ground electrode electrically connected to ground, the wiring electrodes of the third and fifth IDT electrodes being disposed adjacent to the ground electrode of the fourth IDT electrode, the wiring electrode of the second IDT electrode being disposed adjacent to the wiring electrode of the third IDT electrode, and the ground electrode of the first IDT electrode being disposed adjacent to the ground electrode of the second IDT electrode, the unbalanced signal terminal being connected to the wiring electrode of each of the first, third, and fifth IDT electrodes, the first balanced signal terminal being electrically connected to the wiring electrode of the second IDT electrode, and the second balanced signal terminal being electrically connected to the wiring electrode of the fourth IDT electrode, a first pitch gradation of pitch spacing between electrode fingers in each of the first IDT electrode, the second IDT electrode, and the third IDT electrode on a first side of a center line in the third IDT electrode being gradually reduced by a first spacing α as a distance from the center line increases, and a second pitch gradation of pitch spacing between electrode fingers in each of the fourth IDT electrode and the fifth IDT electrode and the electrode fingers in the third IDT electrode on a second side of the center line being gradually reduced by a second spacing β as the distance from the center line increases, where α and β are different.