Patent ID: 8427259
Filing Date: 2013-04-23
Classification: H03H

Abstract:
1. An elastic wave filter comprising: an unbalanced signal terminal; a first interdigital transducer (IDT) electrode, a second IDT electrode, and a third IDT electrode whose wiring electrodes are electrically connected to the unbalanced signal terminal; a fourth IDT electrode disposed between the first IDT electrode and the second IDT electrode; a fifth IDT electrode disposed between the second IDT electrode and the third IDT electrode; a first balanced signal terminal electrically connected to a wiring electrode of the fourth IDT electrode; and a second balanced signal terminal electrically connected to a wiring electrode of the fifth IDT electrode, wherein respective ground electrodes of the first IDT electrode, the second IDT electrode, the third IDT electrode, the fourth IDT electrode, and the fifth IDT electrode are electrically connected to a ground, wherein a signal in opposite phase with a signal input from the unbalanced signal terminal is output from the first balanced signal terminal, wherein a signal in phase with the signal input from the unbalanced signal terminal is output from the second balanced signal terminal, wherein the respective wiring electrodes of the second IDT electrode and the third IDT electrode are adjacent to the ground electrode of the fifth IDT electrode, wherein the wiring electrode of one of the first IDT electrode and the second IDT electrode is adjacent to the wiring electrode of the fourth IDT electrode, wherein the ground electrode of the other of the first IDT electrode and the second IDT electrode is adjacent to the ground electrode of the fourth IDT electrode, wherein concerning a pitch spacing between electrode fingers in each of the first IDT electrode, the second IDT electrode, the third IDT electrode, the fourth IDT electrode, and the fifth IDT electrode, with respect to a center line in the second IDT electrode, the pitch spacings in the pitch gradation on one side are gradually reduced by spacing a as the distance from the center line increases and the pitch spacings in the pitch gradation on the other side are gradually reduced by spacing β as the distance from the center line increases, where α and β are different.