An object of the present invention is to realize a resonator-type SAW filter permitting higher extra-passband suppressibility by minimizing occurrence of an unwanted spurious peak. A resonator-type SAW filter in which a plurality of SAW resonators each having reflectors and an interdigital transducer and being connected in series and parallel with the other, wherein in at least one of the SAW resonators, particularly in at least one of the SAW resonators connected in series with one another, an inter-electrode pitch λ REF in the reflectors has a different value from an inter-electrode pitch λ IDT in the interdigital transducers.

Resonator-type surface-acoustic-wave filter for reducing the signal strength of a spurious peak

A surface acoustic wave filter device suitable for CDMA communication system includes a piezoelectric substrate, and a unidirectional input side transducer and a bidirectional output side transducer are formed on the substrate. The filter device has satisfactory filtering characteristics in terms of insertion loss, frequency characteristic, T.T.E. attenuation level, group delay time, etc.

Surface acoustic wave filter having unidirectional and bidirectional transducers

PURPOSE:To obtain a symmetric frequency feature by eliminating the difference of the sound speed in a weighting electrode and that in a single phase one-way electrode in a surface acoustic wave filter used for a communication unit and the like. CONSTITUTION:The weighting electrode 7 composed of an interdigital transducer 1c and a dummy electrode 6, which are provided on a piezoelectric substrate 3, and the single phase one-way electrode 8 composed of an interdigital transducer 1d and a reflector 2, which are provided on the piezoelectric substrate 3, are provided. Thus, the pitch size (m) of the interdigital transducer 1c is made longer than the pitch size (n) of the interdigital transducer 1d by a ratio between the speed of sound in the single phase one-way electrode and that in the weighting electrode, and therefore the filter feature is made symmetric.

Inoue Akihiko

Papers

Surface acoustic wave filter