A surface acoustic wave filter has a plurality of interdigital transducers
arranged in a ladder circuit structure. Each of the interdigital
transducers has a first comb-shaped electrode and a second comb-shaped
electrode, each of which has a plurality of electrode fingers and a bus
bar connected to first ends of the plurality of electrode fingers. The
first and second comb-shaped electrodes interdigitate with each other so
that second ends of the plurality of electrode fingers of the first
comb-shaped electrode extend toward the bus bar of the second comb-shaped
electrode. A gap is created in at least one of the interdigital
transducers to cause a ripple in the pass band of the surface acoustic
wave filter such that the ripple increases the steepness of the filter
characteristics at the high frequency shoulder of the pass band. The gap
is defined between the bus bar of the first comb-shaped electrode and the
second ends of the plurality of electrode fingers of the second
comb-shaped electrode. The gap width should be in the range of about 0.50
.lambda. to about 4 .lambda., wherein .lambda. is a wavelength of a
surface acoustic wave to be excited on the piezoelectric substrate.