Patent ID: 8416036

Claim:
A branching filter comprising: an antenna terminal; a transmission signal terminal; first and second reception balanced signal terminals; a wiring substrate including first and second main surfaces; a ladder elastic wave filter chip mounted on the first main surface of the wiring substrate and including a first piezoelectric substrate and a ladder elastic wave filter that is provided on the first piezoelectric substrate, the ladder elastic wave filter chip being connected between the antenna terminal and the transmission signal terminal; and a longitudinally-coupled-resonator-type elastic wave filter chip mounted on the first main surface of the wiring substrate; wherein the wiring substrate includes an antenna back-surface electrode provided on the second main surface and connected to the antenna terminal, and a first wiring connected to the antenna back-surface electrode; the longitudinally-coupled-resonator-type elastic wave filter chip includes: a second piezoelectric substrate; a longitudinally-coupled-resonator-type elastic wave filter provided on the second piezoelectric substrate, connected between the antenna terminal and the first and second reception balanced signal terminals, and being configured to have a balanced-unbalanced transformation function; an antenna electrode pad provided on the second piezoelectric substrate and connected to the antenna back-surface electrode through the first wiring; and a second wiring provided on the second piezoelectric substrate and connecting the antenna electrode pad and the longitudinally-coupled-resonator-type elastic wave filter; the longitudinally-coupled-resonator-type elastic wave filter includes a first functional electrode that is connected between the second wiring and the first reception balanced signal terminal and a second functional electrode that is connected between the second wiring and the second reception balanced signal terminal; the second wiring extends in a first direction, and the first functional electrode and the second functional electrode are axisymmetrically arranged with respect to each other about a central axis that extends in the first direction of the second wiring; the ladder elastic wave filter chip has a long narrow shape with a longitudinal direction that is parallel or substantially parallel to a second direction perpendicular or substantially perpendicular to the first direction; and the first wiring includes a portion that is directly connected to the antenna electrode pad, is disposed inside the wiring substrate, and extends in the first direction.