Branching filter
A branching filter includes an antenna terminal, a transmission signal terminal, a reception signal terminal, a transmission filter element, and a reception filter element. At least one of the transmission filter element and the reception filter element includes a longitudinally coupled resonator filter element having first and second IDT electrodes arranged along a direction of propagation of an elastic wave. The first IDT electrode includes a first end connected to the antenna terminal. The second IDT electrode includes a first end connected to one of the transmission signal terminal and the reception signal terminal. The longitudinally coupled resonator filter element further includes an inductor connected in series between a second end of the first IDT electrode and a ground potential.
1. A branching filter comprising:
an antenna terminal;
a transmission signal terminal;
a reception signal terminal;
a transmission filter element disposed between the antenna terminal and the transmission signal terminal; and
a reception filter element disposed between the antenna terminal and the reception signal terminal; wherein
at least one of the transmission filter element and the reception filter element includes a longitudinally coupled resonator filter element including first and second IDT electrodes arranged along a direction of propagation of an elastic wave, the first IDT electrode having a first end connected to the antenna terminal, the second IDT electrode having a first end connected to one of the transmission signal terminal and the reception signal terminal;
the longitudinally coupled resonator filter element further includes an inductor connected in series between a second end of the first IDT electrode and a ground potential and arranged to provide an attenuation range in a region higher than a pass band of the at least one of the transmission filter element and the reception filter element; and
the reception filter element includes the longitudinally coupled resonator filter element, and the transmission filter element includes a ladder filter element.
2. The branching filter according to claim 1 , wherein the inductor is connected to a first ground electrode, and the second IDT electrode includes a second end connected to a second ground electrode separated from the first ground electrode.