Saw resonator having a broad bandwidth

Abstract

A SAW resonator includes resonating SAW transducer units formed on a piezoelectric substrate and juxtaposed in a direction of propagation of acoustic waves, and a unidirectionally reflecting SAW transducer unit provided in each end of the juxtaposed resonating SAW transducer units on the substrate. Each resonating SAW transducer unit includes first and second SAW transducers connected in series and/or in parallel with each other. Each unidirectionally reflecting SAW transducer unit includes first and second comb-like electrodes having a plurality of first second fingers, respectively, formed on the substrate, in which: two second fingers are interposed between each pair of adjacent two first fingers; at least one reflective stripe is provided between the two second fingers interposed between at least one pair of adjacent two first fingers; and the distances between the reflective stripe and the two second fingers and the widths of the two second fingers are determined such that acoustic waves produced by the fingers of the reflecting SAW transducer units and propagating in a first direction perpendicular to the direction of the length of the fingers and reflected by the reflective stripe in a second direction perpendicular to the first direction are in phase with acoustic waves propagating in the second direction and acoustic waves produced by the fingers of the reflecting SAW transducer units and propagating in the second direction and reflected by the reflective stripe in the first direction are out of phase with acoustic waves propagating in the first direction.