Surface acoustic wave device having interdigitated comb electrodes weighted for odd/even response

Claim 1

A surface acoustic wave device, comprising: (A) a piezoelectric substrate for propagating acoustic waves; (B) input and output side electrodes disposed on a surface of said substrate and located laterally with respect to one another along a propagating direction of said acoustic waves; (C) at least one of said input and output side electrodes comprising first and second interdigital electrodes: (i) said first interdigital electrode including a pair of comb electrodes, each of said comb electrodes of said first interdigital electrode including a respective common electrode extending generally along said propagating direction and a plurality of electrode fingers coupled thereto, each of said electrode fingers extending in a direction generally perpendicular to said propagating direction, each of said fingers overlapping adjacent fingers of the remaining comb electrode of the pair, the overlapping length of adjacent fingers being so weighted as to define one of odd and even components of a desired frequency characteristic, said first interdigital electrode lying within an imaginary rectangle whose length is defined by the distance between the most distant electrode fingers of said first interdigital electrode as measured in said propagating direction and whose width is defined by maximum distance between said common electrodes as measured along said direction perpendicular to said propagating direction; (ii) said second interdigital electrode including a pair of comb electrodes, each of said comb electrodes including a respective common electrode extending generally along said propagating direction and a plurality of electrode fingers coupled thereto, said electrode fingers extending in a direction generally perpendicular to said propagating direction, each of said fingers of said second interdigital electrode overlapping adjacent fingers of the remaining comb electrode of said second interdigital electrode, the overlapping length of adjacent fingers being so weighted as to define the other of said odd and even components of said desired response frequency characteristic, said overlapping portions of said electrode fingers of said second interdigital electrode lying entirely within said imaginary rectangle but outside said overlapping region of said fingers of said first interdigital electrode.