Patent ID: 7764144

Claim:
An elastic wave filter comprising: an input side tapered IDT electrode which includes a pair of bus bars formed in parallel to each other and electrode fingers extending from each of the pair of bus bars to be shaped in comb teeth, and which is formed in a manner that the width of the electrode finger and a space area between the electrode fingers are widened gradually from one bus bar toward the other bus bar; an output side tapered IDT electrode being disposed separately from the input side tapered IDT electrode with a space in the direction of propagation of the elastic wave, which includes a pair of bus bars formed in parallel to each other and electrode fingers extending from each of the pair of bus bars to be shaped in comb teeth, and which is formed in a manner that the width of the electrode finger and a space area between the electrode fingers are widened gradually from the one bus bar toward the other bus bar; a short grating electrode provided between the input side tapered IDT electrode and the output side tapered IDT electrode; arranging the one bus bar of the input side tapered IDT electrode and the one bus bar of the output side tapered IDT electrode in the direction of propagation of the elastic wave; and forming an arrangement pattern of the electrode fingers in the short grating electrode in a manner that the arrangement pattern of the electrode fingers of at least either the input side tapered IDT electrode or the output side tapered IDT electrode is continuously extended.