BALANCED SURFACE ACOUSTIC WAVE FILTER

摘要

A balanced acoustic wave filter device that has a balanced-to-unbalanced conversion function and that is capable of reducing the insertion loss in a pass band is provided. A balanced acoustic wave filter device (1) is provided. In the balanced acoustic wave filter device (1), first and second acoustic wave filter sections (6 and 7) that are connected in parallel to an unbalanced terminal (3) are connected to first and second balanced terminals, respectively. The first and second surface acoustic wave filter sections (6 and 7) are configured such that the phases of the first and second balanced terminals (4 and 5) differ by 180 degrees. The first and second acoustic wave filter sections (6 and 7) are longitudinally coupled resonator-type acoustic wave filter sections each including a plurality of IDTS disposed in a direction in which acoustic waves propagate. The total number of pairs of electrode fingers of the IDTS in the second acoustic wave filter section (7) in which the polarities of electrode fingers that are adjacent to each other in an area in which IDTs are adjacent to each other are opposite to each other is greater than the total number of pairs of electrode fingers of the IDTs in the first acoustic wave filter section (6) in which the polarities of electrode fingers that are adjacent to each other in an area in which IDTS are adjacent to each other in the direction in which acoustic waves propagate are equal to each other.