Hitachi, Ltd.

Takemitsu Buma

Jun Yamada

Takashi Shiba

Norio Hosaka

A surface acoustic wave resonator has two solid-type interdigital transducers and two grating reflectors arranged on a piezoelectric substrate or on a surface acoustic wave substrate which contains a piezoelectric material and the reflectors are arranged outside these transducers. If the electrode pitch of the interdigital transducers is suitably different from the pitch of grating of the reflectors, ripples caused by the triple transit echo at frequencies other than the peak frequency are deviated so as to lie outside the stop band of the reflectors, so that spurious responses are suppressed. In this case, the number of electrode pairs Ni of the interdigital transducers should satisfy a relation, Ni.gtoreq..pi./.epsilon., wherein .epsilon. denotes a characteristic mechanical impedance mismatch contribution on the surface of the electrode and on the free surface in the interdigital transducers, so that a peak caused by the trapping of energy in the interdigital transducers is brought into agreement with a peak caused by the triple transit echo to decrease the losses and to increase the Q value.

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Yokohama, Japan

Takemitsu Buma