Surface acoustic wave filter and surface acoustic wave duplexer having the same

摘要

A surface acoustic wave filter includes a series-arm resonators and parallel-arm resonators that are connected in a ladder-like structure, each having an interdigital transducer formed on a piezoelectric substrate, and at least one of the series-arm resonators having a different static capacitance from the other series-arm resonators. In this surface acoustic wave filter, at least one of the series-arm resonators except the series-arm resonator located at the first stage in the ladder-like structure has a lower average resonant frequency than the other series-arm resonators.