Elastic wave filter, and duplexer and electronic device using same

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.