Patent ID: 7876178

Claim:
A composite filter comprising: a piezoelectric substrate; a surface acoustic wave filter; an LC filter coupled to the surface acoustic wave filter; and a laminated substrate; wherein the surface acoustic wave filter is formed by combining surface acoustic wave resonators having comb-shaped electrodes that oppose each other along a first opposing direction on the piezoelectric substrate; wherein the LC filter comprises a π-shaped LC filter formed of a first capacitor and a second capacitor coupled to an inductor in a π-shape, and a third capacitor coupled in parallel to the inductor; wherein at least one of the first, second and third capacitors is formed of comb-shaped electrodes opposed to each other along a second opposing direction on the piezoelectric substrate, and the second opposing direction of the comb-shaped electrodes differs from the first opposing direction of the comb-shaped electrodes of the surface acoustic wave resonators; wherein the piezoelectric substrate is provided with a first grounding conductor disposed at a place not confronting a top face or an underside of the inductor, and the first and second capacitors of the π-shaped LC filter are coupled to the first grounding conductor; and wherein other inductors coupled to the first and second capacitors respectively are provided by coupling a second grounding conductor embedded in the laminated substrate with the first grounding conductor.