Patent ID: 8791774

Claim:
A branching filter comprising: an antenna terminal; a transmission signal terminal; a reception signal terminal; a ladder-type elastic wave filter unit connected between the antenna terminal and the transmission signal terminal; and a longitudinally coupled resonator-type elastic wave filter unit connected between the antenna terminal and the reception signal terminal; wherein the ladder-type elastic wave filter unit comprises: a plurality of series arm resonators connected in series with each other between the antenna terminal and the transmission signal terminal, the series arm resonators defining a series arm; and a parallel arm resonator connected between the series arm and a ground potential; the longitudinally coupled resonator-type elastic wave filter unit comprises first and second functional electrode units, the first and second functional electrode units each comprising at least one IDT electrode connected between the antenna terminal and the reception signal terminal; a transmission signal propagation direction that is perpendicular or substantially perpendicular to an elastic wave propagation direction in the series arm resonators is perpendicular or substantially perpendicular to each of a first reception signal propagation direction that is perpendicular or substantially perpendicular to an elastic wave propagation direction in the first functional electrode unit and a second reception signal propagation direction that is perpendicular or substantially perpendicular to an elastic wave propagation direction in the second functional electrode unit; the ladder-type elastic wave filter unit has an elongated shape whose length direction extends along the transmission signal propagation direction; the longitudinally coupled resonator-type elastic wave filter unit has an elongated shape whose length direction extends along the elastic wave propagation directions in the first and second functional electrode units; the ladder-type elastic wave filter unit further comprises a piezoelectric substrate including the series arm resonators and the parallel arm resonator provided thereon; the longitudinally coupled resonator-type elastic wave filter unit further comprises a piezoelectric substrate including the first and second functional electrode units provided thereon; the piezoelectric substrate of the ladder-type elastic wave filter unit has a rectangular or substantially rectangular shape whose length direction extends along the transmission signal propagation direction; and the piezoelectric substrate of the longitudinally coupled resonator-type elastic wave filter unit has a rectangular or substantially rectangular shape whose length direction extends along the elastic wave propagation directions in the first and second functional electrode units.