Acoustic wave filter device and duplexer

An acoustic wave filter device comprising:

• a piezoelectric substrate;
• at least one first longitudinally coupled resonator acoustic wave filter;
• and
• at least one second longitudinally coupled resonator acoustic wave filter;
• wherein
• the first longitudinally coupled resonator acoustic wave filter includes an input terminal, an output terminal, an IDT connected to the input terminal, and an IDT connected to the output terminal;
• on the piezoelectric substrate, the IDT of the first longitudinally coupled resonator acoustic wave filter connected to the input terminal and the IDT of the first longitudinally coupled resonator acoustic wave filter connected to the output terminal are alternately arranged along an acoustic wave propagating direction, and the output terminal or the input terminal of the first longitudinally coupled resonator acoustic wave filter is connected to a first balanced signal terminal;
• the second longitudinally coupled resonator acoustic wave filter includes an input terminal, an output terminal, an IDT connected to the input terminal, and an IDT connected to the output terminal;
• on the piezoelectric substrate, the IDT of the second longitudinally coupled resonator acoustic wave filter connected to the input terminal and the IDT of the second longitudinally coupled resonator acoustic wave filter connected to the output terminal are alternately arranged along the acoustic wave propagating direction, the output terminal or the input terminal of the second longitudinally coupled resonator acoustic wave filter is connected to a second balanced signal terminal, and the phase of the second longitudinally coupled resonator acoustic wave filter is different by 180° from the phase of the first longitudinally coupled resonator acoustic wave filter;
• the input terminals or the output terminals of the first and second longitudinally coupled resonator acoustic wave filters are connected to an unbalanced signal terminal;
• and
• wherein the first and second longitudinally coupled resonator acoustic wave filters are withdrawal-weighted, and the withdrawal weighting in at least one of the first and second longitudinally coupled resonator acoustic wave filters is different from the withdrawal weighting in the other longitudinally coupled resonator acoustic wave filter.

An acoustic wave filter device comprising:

• a piezoelectric substrate;
• and
• first to fourth longitudinally coupled resonator acoustic wave filters, an unbalanced signal terminal, and first and second balanced signal terminals, provided on the piezoelectric substrate;
• wherein
• each of the first to fourth longitudinally coupled resonator acoustic wave filters is provided on the piezoelectric substrate and includes a first IDT connected to one of an input terminal and an output terminal of the corresponding one of the first to fourth longitudinally coupled resonator acoustic wave filters and second IDTs provided on both sides of the first IDT in an acoustic wave propagating direction and connected to the other of the input terminal and the output terminal;
• the input terminals of the first and second longitudinally coupled resonator acoustic wave filters are connected to the unbalanced signal terminal, the output terminal of the third longitudinally coupled resonator acoustic wave filter is connected to the first balanced signal terminal, and the output terminal of the fourth longitudinally coupled resonator acoustic wave filter is connected to the second balanced signal terminal;
• the output terminal of the first longitudinally coupled resonator acoustic wave filter is connected to the input terminal of the third longitudinally coupled resonator acoustic wave filter, and the output terminal of the second longitudinally coupled resonator acoustic wave filter is connected to the input terminal of the fourth longitudinally coupled resonator acoustic wave filter;
• the phase of one of the first to fourth longitudinally coupled resonator acoustic wave filters is inverted with respect to the phases of the other longitudinally coupled resonator acoustic wave filters;
• and
• the first and second longitudinally coupled resonator acoustic wave filters are withdrawal-weighted, and the withdrawal weighting in the first longitudinally coupled resonator acoustic wave filter is different from the withdrawal weighting in the second longitudinally coupled resonator acoustic wave filter.

An acoustic wave filter device comprising:

• a piezoelectric substrate;
• and
• first to fourth longitudinally coupled resonator acoustic wave filters, an unbalanced signal terminal, and first and second balanced signal terminals, provided on the piezoelectric substrate;
• wherein
• each of the first to fourth longitudinally coupled resonator acoustic wave filters is provided on the piezoelectric substrate and includes a first IDT connected to one of an input terminal and an output terminal of the corresponding one of the first to fourth longitudinally coupled resonator acoustic wave filters and second IDTs provided on both sides of the first IDT in an acoustic wave propagating direction and connected to the other of the input terminal and the output terminal;
• the input terminals of the first and second longitudinally coupled resonator acoustic wave filters are connected to the unbalanced signal terminal, the output terminal of the third longitudinally coupled resonator acoustic wave filter is connected to the first balanced signal terminal, and the output terminal of the fourth longitudinally coupled resonator acoustic wave filter is connected to the second balanced signal terminal;
• the output terminal of the first longitudinally coupled resonator acoustic wave filter is connected to the input terminal of the third longitudinally coupled resonator acoustic wave filter, and the output terminal of the second longitudinally coupled resonator acoustic wave filter is connected to the input terminal of the fourth longitudinally coupled resonator acoustic wave filter;
• the phase of one of the first to fourth longitudinally coupled resonator acoustic wave filters is inverted with respect to the phases of the other longitudinally coupled resonator acoustic wave filters;
• and
• the third and fourth longitudinally coupled resonator acoustic wave filters are withdrawal-weighted, and the withdrawal weighting in the third longitudinally coupled resonator acoustic wave filter is different from the withdrawal weighting in the fourth longitudinally coupled resonator acoustic wave filter.