Patent ID: 6137380
Filing Date: 2000-10-24
Classification: H03H

Abstract:
A surface acoustic wave filter comprising:a surface acoustic wave substrate;an input terminal;an output terminal;a ground terminal;a series resonator disposed on the surface acoustic wave substrate and having a resonant frequency and an antiresonant frequency, the series resonator being electrically disposed between the input terminal and the output terminal in series so as to define a series arm; anda first parallel resonator disposed on the surface acoustic wave substrate having a resonant frequency and an antiresonant frequency which is substantially identical to the resonant frequency of the series resonator, the first parallel resonator being electrically disposed between the series arm and a ground terminal so as to define a first parallel arm, the series arm and the first parallel arm constituting a ladder circuit such that the surface acoustic wave filter has a predetermined pass band;wherein the first parallel resonator has a spurious component at a frequency located between the resonant frequency of the first parallel resonator and a low end of the passband of the surface acoustic wave filter or at a frequency located between the antiresonant frequency of the series resonator and a high end of the passband of the surface acoustic wave filter.