Surface acoustic wave filter and branching filter utilizing it

摘要

Disclosed is a surface acoustic wave filter having a first serial-arm SAW resonator coupled to an input terminal and a first dual-mode SAW resonator coupled between the first serial-arm SAW resonator and an output terminal, wherein the first dual-mode SAW resonator includes first to third comb-shaped interdigital transducers, the second comb-shaped interdigital transducer is arranged between the first and third comb-shaped interdigital transducers and also coupled between the first serial-arm SAW resonator and the ground potential, and each of the first and third comb-shaped interdigital transducers is coupled between the ground potential and the output terminal. Also disclosed is a branching filter utilizing the surface acoustic wave filter.