Patent ID: 8773221

Claim:
A band rejection filter comprising: a ladder circuit including: a series arm arranged to connect an input terminal and an output terminal to each other; a parallel arm which is connected between the series arm and a ground potential; a plurality of elastic wave resonators which are disposed in at least one of the series arm and the parallel arm; an inductance element which is disposed in at least one of the series arm and the parallel arm; and a first attenuation band, a first passband which is provided by an inductance of the inductance element and adjacent to the first attenuation band, a second attenuation band which is provided by resonances of the plurality of elastic wave resonators and included in the first passband, and a transition band which is adjacent to the second attenuation band; wherein at least one of the elastic wave resonators which contributes to formation of the transition band has a propagation angle larger than propagation angles of the others of the elastic wave resonators; and the at least one of the elastic wave resonators having the propagation angle larger than the propagation angles of the others of the elastic wave resonators includes one of an elastic wave resonator of the plurality of elastic wave resonators which has a lowest resonant frequency and an elastic wave resonator of the plurality of elastic wave resonators which has a highest anti-resonant frequency.