Patent ID: 7286028

Claim:
A surface acoustic wave (SAW) filter comprising: a first SAW resonator; a second SAW resonator connected in series to said first SAW resonator at a first node; a third SAW resonator connected in series to said second SAW resonator at a second node; a fourth SAW resonator connected in series to said third SAW resonator at a third node; a fifth SAW resonator connected between the first node and a ground; a sixth SAW resonator connected between the third node and a ground; a first capacitance element having a capacitance and being connected between the second node and a ground; a first inductance element connect between said fifth SAW resonator and the ground such that said fifth SAW resonator and said first inductance element are connected in series; a second inductance element connected between said sixth SAW resonator and the ground such that said sixth SAW resonator and said second inductance element are connected in series; a piezoelectric board having a surface including said first to sixth SAW resonators and said first capacitance element disposed thereon; a first electrode, arranged on said surface of said piezoelectric board, and extending from one of the second node and the ground, said first electrode having a first edge; and a second electrode, arranged on said surface of said piezoelectric board, and extending from another of the second node and the ground, said second electrode having a second edge parallel to and facing said first edge of said first electrode, wherein said first capacitance element includes: a third electrode, arranged on said surface of said piezoelectric board, and extending from said first edge of said first electrode; and a fourth electrode, arranged on said surface of said piezoelectric board, extending from said second edge of said second electrode, and facing said third electrode in a direction perpendicular to said first and second edges with a gap formed therebetween.