Patent ID: 7868715

Claim:
A duplexer comprising: a first filter element, being placed on a piezoelectric substrate, having a ladder-type structure in which a plurality of resonators having a pair of comb-shaped electrode fingers is disposed on a series arm and one or a plurality of parallel arms, wherein said plurality of resonators of said first filter element is arranged so as to have a longitudinal direction thereof along a propagating direction of an elastic surface wave of said piezoelectric substrate; and a second filter element having a frequency pass band higher than that of said first filter element, being placed on said piezoelectric substrate so as to be made face to face with said first filter element, having a ladder-type structure in which a plurality of resonators having a pair of comb-shaped electrode fingers is disposed on a series arm and one or a plurality of parallel arms, wherein said plurality of resonators of said second filter element is arranged so as to have the a longitudinal direction thereof along a propagating direction of an elastic surface wave of said piezoelectric substrate, and one or the plurality of resonators placed on said one or the plurality of parallel arms of said second filter element is disposed at a position that deviates from an elastic wave propagating path of the resonator having the largest width in the elastic wave propagating path among resonators placed on said series arm of said first filter element on said piezoelectric substrate.