Surface acoustic wave device and communications apparatus

摘要

A surface acoustic wave (SAW) device includes at least one longitudinally coupled resonator SAW filter (201) and at least one SAW resonator (223) connected in series to the SAW filter (201) on a piezoelectric substrate. The SAW resonator (223) is set so that the resonant frequency is located within the pass band of the SAW filter (201) and the antiresonant frequency is located outside the pass band of the SAW filter. A dummy electrode (228) is provided between an electrode finger and a bus bar of an interdigital transducer (IDT) of the SAW resonator (223). The gap between the dummy electrode (228) and the electrode finger of the IDT is set to be 0.5 lambda or smaller when the wavelength determined by the pitch between the electrode fingers of the interdigital transducers of the SAW resonator (223) is indicated by lambda .