Patent ID: 6535080
Filing Date: 2003-03-18
Classification: H03H

Abstract:
A surface acoustic wave filter comprising:a piezoelectric substrate; and a plurality of surface acoustic wave resonators provided on said piezoelectric substrate and connected to define a ladder filter circuit; wherein the ladder filter circuit includes: input-side balanced signal terminals A1 and A2 connected to an external balanced circuit; output-side balanced signal terminals B1 and B2 connected to an external balanced circuit; at least one first series arm surface acoustic wave resonator connected in series between said input-side balanced signal terminal A1 and said output-side balanced signal terminal B1; at least one second series arm surface acoustic wave resonator connected in series between said input-side balanced signal terminal A2 and said output-side balanced signal terminal B2; and at least one impedance element connected between a first signal line connecting said input-side balanced signal terminal A1 to said output-side balanced signal terminal B1 and a second signal line connecting said input-side balanced signal terminal A2 to said output-side balanced signal terminal B2; wherein said at least one impedance element is a capacitance element.