Patent ID: 11043933

Abstract:
A notch filter includes a substrate having piezoelectricity, the substrate including a high-acoustic-velocity member, a low-acoustic-velocity film provided on the high-acoustic-velocity member, and a piezoelectric thin film provided on the low-acoustic-velocity film; an interdigital transducer electrode provided on the piezoelectric thin film; and reflectors provided on both sides of the interdigital transducer electrode in an acoustic wave propagation direction. An IR gap is within one of two ranges: 0.1λ≤GIR<0.5λ or 0.5λ<GIR≤0.9λ, where λ is a wavelength determined by an electrode finger pitch of the interdigital transducer electrode, and the IR gap is a distance between electrode finger centers of an electrode finger of the interdigital transducer electrode closest to the reflector out of the electrode fingers of the interdigital transducer electrode, and an electrode finger of the reflector closest to the interdigital transducer electrode, out of the electrode fingers of the reflector.