LONGITUDINALLY COUPLED RESONATOR TYPE SURFACE ACOUSTIC WAVE FILTER DEVICE

摘要

There is provided a longitudinally-coupled-resonator-type elastic wave filter device that includes a series-weighted IDT and can suppress the generation of ripples in a pass hand. In a longitudinally-coupled-resonator-type elastic wave filter device, at least one of an IDT (113) and an IDT (114) which are adjacent to each other is provided with a dummy electrode (116 or 118) for series weighting in a portion in which the IDTs (113 and 114) are adjacent to each other, and at least one of series-weighted portions includes at least one of metallization ratio reducing means in a first acoustic track and metallization ratio increasing means in a second acoustic track so as to reduce the difference between the metallization ratio of the first acoustic track passing through a connecting portion (116c) of the dummy electrode (116) and the metallization ratio of each of second and third acoustic tracks each placed on either side of the first acoustic track in the direction of propagation of an elastic wave.