Elastic-wave filter device

摘要

An elastic-wave filter device includes a reception filter section including a longitudinally coupled resonator-type elastic-wave filter section that has a balanced-to-unbalanced conversion function and has improved common-mode isolation characteristics. Among IDT electrodes of a filter section, each of the other comb-shaped electrode of a first IDT electrode including a pair of comb-shaped electrodes, one of which is connected to a first balanced-signal terminal, and the other comb-shaped electrode of a second IDT electrode including a pair of comb-shaped electrodes, one of which is connected to a second balanced-signal terminal, is connected to one of ground electrodes that are provided on a piezoelectric substrate. Inductors are provided on the piezoelectric substrate, and each inductor is connected between the other comb-shaped electrode of one of the first and second IDT electrodes and one of the ground electrodes.

主权项

1. An elastic-wave filter device comprising:
an antenna terminal; first and second balanced-signal terminals; and a reception filter section that is connected between the antenna terminal and the first and second balanced-signal terminals; wherein the reception filter section includes a longitudinally coupled resonator elastic-wave filter section that includes a piezoelectric substrate and a plurality of IDT electrodes provided on the piezoelectric substrate and each of which includes a pair of comb-shaped electrodes; among the plurality of IDT electrodes, a first comb-shaped electrode of a first IDT electrode including the pair of comb-shaped electrodes, one of which is connected to the first balanced-signal terminal, is connected to a corresponding first one of a plurality of ground electrodes that are provided on the piezoelectric substrate, and a first comb-shaped electrode of a second IDT electrode including the pair of comb-shaped electrodes, one of which is connected to the second balanced-signal terminal, is connected to a different corresponding second one of the ground electrodes provided on the piezoelectric substrate; and the elastic-wave filter device further comprises:
a first elastic-wave resonator that includes the piezoelectric substrate and an IDT electrode which is provided on the piezoelectric substrate and which is connected between a node between the reception filter section and the first balanced-signal terminal and the corresponding first one of the ground electrodes;a second elastic-wave resonator that includes the piezoelectric substrate and an IDT electrode which is provided on the piezoelectric substrate and which is connected between a node between the reception filter section and the second balanced-signal terminal and the corresponding second one of the ground electrodes; andinductors which are provided on the piezoelectric substrate and each of which is connected between the first comb-shaped electrode of a corresponding one of the first and second IDT electrodes and the corresponding first and second ones of the ground electrodes.