SURFACE ACOUSTIC WAVE RESONATOR AND SURFACE ACOUSTIC WAVE FILTER USING THE RESONATOR

摘要

PROBLEM TO BE SOLVED: To provide a ladder-type surface acoustic wave filter with higher angle ratio than conventional filters, by making the resonant frequency closer to the antiresonant frequency in a surface acoustic wave resonator. SOLUTION: This surface acoustic wave filter is made up of a piezoelectric substrate, a comb-shaped electrode consisting of electrode fingers having the period pi that is almost as long as the wavelength of the surface acoustic wave to be excited, and at least one reflector which is arranged near the comb-shaped electrode in a manner that it can reflect the surface acoustic wave in parallel with the forwarding direction of the excited surface acoustic wave from the comb-shaped electrode. This filter features that the comb-shaped electrode has three or more electrode fingers in the period pi, and that the reflector consists of a plurality of gratings having the period pr that is half as long as the wavelength of the surface acoustic wave coming through the reflector.