Acoustic wave resonator, acoustic wave filter, multiplexer, and communication apparatus

An acoustic wave resonator, comprising:

• a piezoelectric substrate,
• an IDT electrode comprising pluralities of electrode fingers aligned in a direction of propagation of an acoustic wave on the piezoelectric substrate, and
• a pair of reflectors located on the two sides of the pluralities of electrode fingers on the piezoelectric substrate in the direction of propagation, wherein
• the IDT electrode comprises a plurality of areas, a plurality of electrode fingers among the pluralities of electrode fingers being distributed to each of the areas, each of the areas having constant electrode finger pitch, the areas having resonance frequencies different from each other, and,
• between any two areas adjacent to each other among the plurality of areas, an electrode finger in one area at an end part on the other area side and an electrode finger in the other area at an end part on the one area side are two electrode fingers which are adjacent to each other, and the electrode finger pitch of these two electrode fingers is different in size from any of the electrode finger pitches in the two areas and is smaller than an intermediate value between the electrode finger pitches in the two areas, wherein the acoustic wave resonator is a 1-port resonator.

An acoustic wave filter, comprising:

• one or more serial resonators and one or more parallel resonators which are connected in a ladder form, wherein
• at least one of the one or more parallel resonators is configured by an acoustic wave resonator, wherein the acoustic wave resonator, comprising:
• a piezoelectric substrate,
• an IDT electrode comprising pluralities of electrode fingers aligned in a direction of propagation of an acoustic wave on the piezoelectric substrate, and
• a pair of reflectors on two sides of the pluralities of electrode fingers on the piezoelectric substrate in the direction of propagation, wherein
• the IDT electrode further comprising a plurality of areas, a plurality of electrode fingers among the pluralities of electrode fingers being distributed to each of the areas, the areas having resonance frequencies different from each other,
• the plurality of areas comprise at least an area having a lowest resonance frequency among all areas, an area having a highest resonance frequency among all of the areas, and an area having a resonance frequency which is higher than the lowest resonance frequency and is second highest among all of the areas, and
• the second highest resonance frequency is lower than an intermediate value between the lowest resonance frequency and the highest resonance frequency.

A multiplexer, comprising:

• an antenna terminal,
• a transmission filter filtering a transmission signal and outputting the result to the antenna terminal, and
• a receiving filter filtering a reception signal from the antenna terminal, wherein
• at least one of the transmission filter and an acoustic wave filter comprising:
• one or more serial resonators and one or more parallel resonators which are connected in a ladder form, wherein
• at least one of the one or more parallel resonators is configured by an acoustic wave resonator, wherein the acoustic wave resonator, comprising:
• a piezoelectric substrate,
• an IDT electrode comprising pluralities of electrode fingers aligned in a direction of propagation of an acoustic wave on the piezoelectric substrate,
• and a pair of reflectors on two sides of the pluralities of electrode fingers on the piezoelectric substrate in the direction of propagation, wherein
• the IDT electrode further comprising a plurality of areas, a plurality of electrode fingers among the pluralities of electrode fingers being distributed to each of the areas, the areas having resonance frequencies different from each other,
• the plurality of areas comprise at least an area having a lowest resonance frequency among all areas, an area having a highest resonance frequency among all of the areas, and an area having a resonance frequency which is higher than the lowest resonance frequency and is second highest among all of the areas,
• the second highest resonance frequency is lower than an intermediate value between the lowest resonance frequency and the highest resonance frequency,
• a plurality of the parallel resonators each of which is configured by the acoustic wave resonator, wherein
• for the resonance frequency of the area having the lowest resonance frequency, a ratio of a difference between the minimum value and the maximum value among the plurality of parallel resonators relative to an intermediate value between these minimum value and maximum value is larger than a ratio of a difference between the minimum value and the maximum value among the plurality of parallel resonators relative to an intermediate value between these minimum value and maximum value for the resonance frequency of the area having the highest resonance frequency.

A communication apparatus, comprising:

• an antenna,
• a multiplexer, comprising:
• an antenna terminal,
• a transmission filter filtering a transmission signal and outputting the result to the antenna terminal, and
• a receiving filter filtering a reception signal from the antenna terminal, wherein
• at least one of the transmission filter and an acoustic wave filter comprising:
• one or more serial resonators and one or more parallel resonators which are connected in a ladder form, wherein
• at least one of the one or more parallel resonators is configured by an acoustic wave resonator, wherein the acoustic wave resonator, comprising:
• a piezoelectric substrate,
• an IDT electrode comprising pluralities of electrode fingers aligned in a direction of propagation of an acoustic wave on the piezoelectric substrate, and
• a pair of reflectors on two sides of the pluralities of electrode fingers on the piezoelectric substrate in the direction of propagation, wherein
• the IDT electrode further comprising a plurality of areas, a plurality of electrode fingers among the pluralities of electrode fingers being distributed to each of the areas, the areas having resonance frequencies different from each other,
• the plurality of areas comprise at least an area having a lowest resonance frequency among all areas, an area having a highest resonance frequency among all of the areas, and an area having a resonance frequency which is higher than the lowest resonance frequency and is second highest among all of the areas,
• the second highest resonance frequency is lower than an intermediate value between the lowest resonance frequency and the highest resonance frequency,
• a plurality of the parallel resonators each of which is configured by the acoustic wave resonator, wherein
• for the resonance frequency of the area having the lowest resonance frequency, a ratio of a difference between the minimum value and the maximum value among the plurality of parallel resonators relative to an intermediate value between these minimum value and maximum value is larger than a ratio of a difference between the minimum value and the maximum value among the plurality of parallel resonators relative to an intermediate value between these minimum value and maximum value for the resonance frequency of the area having the highest resonance frequency.