Patent ID: 10911024

Abstract:
A SAW filter includes a piezoelectric substrate, a serial arm and a parallel resonance portion. The serial arm includes one or more serial resonance portions. The parallel resonance portion is located on the piezoelectric substrate and configures a ladder-type filter together with the serial arm. The parallel resonance portion includes a parallel resonator and a capacity element. The parallel resonator includes an IDT electrodes on the piezoelectric substrate and a pair of reflectors on the two sides thereof. The capacity element is connected in parallel with the parallel resonator. A capacitance of the capacity element is 0.8 time or more of a capacitance of the IDT electrode in the parallel resonator. A difference between an anti-resonance frequency and a resonance frequency of the first parallel resonance portion is smaller than a difference between an anti-resonance frequency and a resonance frequency of the first parallel resonator.