Patent ID: 9729125
Date: 2017-08-08
CPC Classifications: H03H

Claim:
1. A filter apparatus comprising: an input terminal; an output terminal; a low pass filter connected between the input terminal and the output terminal; and a high pass filter connected in series to the low pass filter between the input terminal and the output terminal; wherein the low pass filter includes: the high pass filter includes: a first attenuation band caused by the anti-resonant frequency of the first acoustic resonator is provided at a low frequency side of a pass band and a second attenuation band caused by the resonant frequency of the second acoustic resonator is provided at a high frequency side of the pass band; a third attenuation band caused by a resonant frequency of the first LC resonant circuit is provided at a low frequency side of the first attenuation band; and a fourth attenuation band caused by a resonant frequency of the second LC resonant circuit is provided at a high frequency side of the second attenuation band.