Patent ID: 7486158

Claim:
A branching filter comprising: a first band-pass filter having a relatively low frequency passband; and a second band-pass filter having a relatively high frequency passband; wherein the first and second band-pass filters each include a surface acoustic wave filter having a ladder circuit structure including series resonators and parallel resonators, and ends of the first and second band-pass filters are connected to one common terminal; the second band-pass filter is a polar filter including: a first parallel resonator having a relatively high impedance Z 1 and a relatively high resonant frequency f 1 ; a second parallel resonator having a relatively low impedance Z 2 and a relatively low resonant frequency f 2 , the second parallel resonator being connected to a parallel arm that is different from that to which the first parallel resonator is connected, a common-connection ground terminal commonly connected to ends of the first parallel resonator and the second parallel resonator, the ends being connected to a ground potential; a first inductance connected between the common-connection ground terminal and the ground potential; a third parallel resonator connected to a parallel arm that is different from those to which the first and second parallel resonators are connected; and a second inductance connected between the third parallel resonator and the ground potential; a relationship f 1 >f 0 >f 2 is satisfied, where f 0 denotes an average of resonant frequencies of all the parallel resonators; and the first inductance and the second inductance are arranged to suppress an occurrence of a ripple at a high frequency side of the passband of the first band-pass filter, thereby achieving a sufficient pass band width.