Patent ID: 7626475

Claim:
A SAW filter device having a trap band and a pass band lower than the trap band, comprising: a filter chip including a θ-rotated Y-cut X-propagation LiNbO 3 substrate and a plurality of one-port SAW resonators provided on the θ-rotated Y-cut X-propagation LiNbO 3 substrate, the plurality of one-port SAW resonators each including an IDT made of one of Al and an Al alloy; wherein a cutting angle θ of the θ-rotated Y-cut X-propagation LiNbO 3 is in a range between about 50° and about 55°, a normalized film thickness of the IDT 100h/λ, expressed in %, wherein h denotes a thickness of the IDT and λ denotes a wavelength of a surface acoustic wave, is in a range between about 2% and about 4%, and a duty ratio of the IDT is less than 0.4.