US Patent 7880566 Balanced lattice filter device

A lattice-type filter circuit includes first and second balanced signal terminals; first and second balanced signal terminals; a first resonator connected to a series arm between the first balanced signal terminal on the input side and the first balanced signal terminal on the output side; a second resonator connected to a series arm between the second balanced signal terminal on the input side and the second balanced signal terminal on the output side; a first resonant circuit including impedance elements, being connected to a lattice arm between the first balanced signal terminal on the output side and the second balanced signal terminal on the input side; and a second resonant circuit including impedance elements, being connected to a lattice arm between the second balanced signal terminal on the output side and the first balanced signal terminal on the input side.