Patent ID: 7369015
Filing Date: 2008-05-06
Classification: H03H

Abstract:
1. A balanced surface acoustic wave filter having an unbalanced terminal and first and second balanced terminals and having a balanced-unbalanced conversion function, comprising: a piezoelectric substrate; and first to fifth IDTs arranged on the piezoelectric substrate along a surface acoustic wave propagation direction; wherein the second and fourth IDTs are connected to the unbalanced terminal, and the second IDT and the fourth IDT have a phase difference of 180° with respect to each other; the third IDT is divided into a first sub-IDT portion and a second sub-IDT portion along the surface acoustic wave propagation direction, the first sub-IDT portion and the first IDT are connected to the first balanced terminal, and the second sub-IDT portion and the fifth IDT are connected to the second balanced terminal; and conditions of 1.55≦N