Acoustic wave filter device
AssigneeMurata Manufacturing Co., Ltd.
InventorKatsuhito Kuroda
Life of this patent
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Abstract
In an acoustic wave filter device, a first filter circuit portion includes a first inductor provided in a series arm that couples an input terminal and an output terminal is serially connected to a first acoustic wave resonator, and a second filter circuit portion includes a second inductor provided in the series arm and second and third acoustic wave resonators and connected between one end and the other end of the second inductor and a ground potential. When the pass band center frequency is set as a first center frequency and the center frequency of a filter defined by the inductance of the first and second inductors and the capacitance of the first to third acoustic wave resonators is set as a second center frequency f2, f1 is less than f2.
Claims7
An acoustic wave filter device having a first attenuation band, a pass band having a first center frequency, the pass band located on a frequency side that is lower than the first attenuation band, and a second attenuation band located on a frequency side that is higher than the first attenuation band, the acoustic wave filter device comprising:
- first filter circuit portions having first inductors provided in a series arm that couples an input terminal and an output terminal and first acoustic wave resonators serially connected to the first inductors;
- and
- a second filter circuit portion having at least one second inductor provided in the series arm, a second acoustic wave resonator connected between one end of the second inductor and a ground potential, and a third acoustic wave resonator connected between the other end of the second inductor and the ground potential;
- wherein
- the first filter circuit portions and the second filter circuit portion are serially connected in the series arm;
- and
- when the center frequency of a frequency characteristic of an LC filter defined by capacitance components of the first, second and third acoustic wave resonators and inductance components of the first and second inductors is a second center frequency, the second center frequency is higher than the first center frequency.
Dependencies are inferred from the claim text.