DUPLEXER

摘要

A duplexer includes a transmission filter with a ladder circuit configuration and a reception filter including a ladder filter portion connected to an antenna terminal and a longitudinally coupled resonator-type surface acoustic wave filter. In the transmission filter, a coupling capacitor is connected between an end portion of an inductor nearer to parallel arm resonators and a wiring line connecting the ladder filter portion to the longitudinally coupled resonator-type surface acoustic wave filter in the reception filter.

主权项

1. A duplexer comprising:
an antenna terminal; a transmission terminal; a reception terminal; a transmission filter that is connected between the antenna terminal and the transmission terminal and that has a ladder circuit configuration including a plurality of elastic wave resonators; a reception filter including a longitudinally coupled resonator filter portion connected between the antenna terminal and the reception terminal and a ladder filter portion connected between the longitudinally coupled resonator filter portion and the antenna terminal; wherein the transmission filter includes a first series arm resonator, a first parallel arm resonator, and an inductor connected between the first parallel arm resonator and a ground potential; the ladder filter portion includes at least two second series arm resonators and a second parallel arm resonator; and the duplexer further includes a coupling capacitor or an elastic wave resonator connected between a wiring line connecting the second series arm resonators of the ladder filter portion to each other and an end portion of the inductor nearer to the first parallel arm resonator.