Patent ID: 8258894

Claim:
A bulk acoustic wave (BAW) filter device, comprising: a first port; a second port; a first coupled resonator filter stage comprising a first BAW resonator connected to the first port and a second BAW resonator acoustically coupled to the first BAW resonator; a second coupled resonator filter stage comprising a third BAW resonator connected to the second port and a fourth BAW resonator acoustically coupled to the third BAW resonator; and a filter section comprising: a fifth BAW resonator, the fifth BAW resonator connected between the second BAW resonator and the fourth BAW resonator a third port and a fourth port, each comprising a first and second terminal; and a shunt BAW resonator or series BAW resonator, wherein the shunt BAW resonator is connected in parallel to the third port or the fourth port and the series BAW resonator connects the first terminals of the third and fourth ports or the series BAW resonator connects the second terminals of the third and fourth ports.