Surface acoustic wave filter

摘要

A surface acoustic wave filter employing surface acoustic wave electrodes for forming a ladder filter circuit according to the invention, the SAW filter comprises a series resonator group including a plurality of surface acoustic wave electrodes formed on a surface of a piezoelectric substrate and electrically disposed in series between an input terminal and an output terminal; and a parallel resonator group including a plurality of surface acoustic wave electrodes individually electrically disposed in parallel between an input- or output-terminal of the individual surface acoustic wave electrodes of the series resonator group and a ground electrode, wherein a part number of the surface acoustic electrodes of the parallel resonator group is configured to deteriorate an obtained Q value and presents a resonant frequency which is lower than an antiresonant frequency and higher than a resonant frequency respectively formed by the other surface acoustic wave electrodes of the parallel resonator group. Thus is obtained a steep shoulder characteristic curve on a lower side of a passband.