Patent ID: 8436778

Claim:
An antenna duplexer comprising: an antenna terminal adapted to be connected with an antenna; a transmission filter connected to the antenna terminal and adapted to be coupled with a transmission circuit; and a reception filter connected to the antenna terminal and adapted to be coupled with the reception circuit, wherein a pass band of the transmission filter is lower than a pass band of the reception filter, the transmission filter includes a first terminal adapted to be coupled with one of the transmission circuit and the antenna terminal, a second terminal adapted to be coupled with one of another of the transmission circuit and the antenna terminal, a first series resonator having a first port and a second port, the first port of the first series resonator being coupled with the first terminal, a second series resonator having a first port and a second port, the first port of the second series resonator being connected to the second port of the first series resonator at a first node, the second port of the second series resonator being coupled with the second terminal, a first parallel resonator having a first port and a second port, the first port of the first parallel resonator being connected to the first port of the first series resonator, a second parallel resonator having a first port and a second port, the first port of the second parallel resonator being connected to the first node, the second port of the second parallel resonator being connected to the second port of the first parallel resonator at a second node, a third parallel resonator having a first port and a second port, the first port of the third parallel resonator being connected to the first node, a fourth parallel resonator having a first port and a second port, the first port of the fourth parallel resonator being connected to the second port of the second series resonator, the second port of the fourth parallel resonator being connected to the second port of the third parallel resonator at a third node, a first inductance element having a first end and a second end, the first end of the first inductance element being connected to the second node, the second end of the first inductance element being coupled with a ground, and a second inductance element having a first end and a second end, the first end of the second inductance element being connected to the third node, the second end of the second inductance element being coupled with the ground, the first parallel resonator, the second parallel resonator, and the first inductance element produce an attenuation pole at a frequency lower than a pass band of the transmission filter, the third parallel resonator, the fourth parallel resonator, and the second inductance element produce an attenuation pole at a frequency higher than a pass band of the transmission filter, and an inductance of the second inductance element is lower than an inductance of the first inductance element.