Acoustic wave filter device

An acoustic wave filter device comprising:

• a piezoelectric substrate;
• a three-IDT longitudinally coupled resonator type first acoustic wave filter portion including first to third IDTs that are arranged on the piezoelectric substrate in this order along an acoustic wave propagating direction, and first and second reflectors that are arranged on both sides of the first to third IDTs in the acoustic wave propagating direction;
• and
• a three-IDT longitudinally coupled resonator type second acoustic wave filter portion including fourth to sixth IDTs that are arranged on the piezoelectric substrate in this order along the acoustic wave propagating direction, and third and fourth reflectors that are arranged on both sides of the fourth to sixth IDTs in the acoustic wave propagating direction;
• wherein
• the second IDT includes first and second divided IDT portions divided in the acoustic wave propagating direction and connected in series with each other, the first divided IDT portion is connected to an unbalanced terminal, and the second divided IDT portion is connected to a ground potential;
• ends of the first and third IDTs are electrically connected to ends of the fourth and sixth IDTs, respectively, and the second acoustic wave filter portion is electrically connected to the first acoustic wave filter portion;
• the fifth IDT includes first and second divided IDT portions divided in the acoustic wave propagating direction, and the first and second divided IDT portions of the fifth IDT are connected to first and second balanced terminals, respectively;
• and
• metallization ratios of the first and second divided IDT portions are different from each other in at least one of the second and fifth IDTs.

An acoustic wave filter device that is a three-IDT longitudinally coupled resonator type acoustic wave filter device, comprising:

• a piezoelectric substrate;
• first to third IDTs arranged on the piezoelectric substrate so as to be arranged in this order along an acoustic wave propagating direction;
• and
• first and second reflectors arranged on both sides of the first to third IDTs in the acoustic wave propagating direction;
• wherein
• the first and third IDTs include first and second divided IDT portions divided in an electrode finger overlap width direction and connected in series with each other, respectively, the first divided IDT portion of the first IDT and the first divided IDT portion of the third IDT are connected in common to an unbalanced terminal, and each of the second divided IDT portions of the first and third IDTs is connected to a ground potential;
• and
• the second IDT includes first and second divided IDT portions divided in the acoustic wave propagating direction, and the first and second divided IDT portions of the second IDT are connected to first and second balanced terminals, respectively.

An acoustic wave filter device that is a five-IDT longitudinally coupled resonator type acoustic wave filter device, comprising:

• a piezoelectric substrate;
• first to fifth IDTs arranged on the piezoelectric substrate in this order along an acoustic wave propagating direction;
• and
• first and second reflectors arranged on both sides of the first to fifth IDTs in the acoustic wave propagating direction;
• wherein
• the first, third, and fifth IDTs include first and second divided IDT portions divided in an electrode finger overlap width direction and connected in series with each other, respectively;
• the first divided IDT portions of the first, third, and fifth IDTs are connected in common to an unbalanced terminal, and each of the second divided IDT portions of the first, third, and fifth IDTs is connected to a ground potential;
• the second and fourth IDTs are connected to first and second balanced terminals, respectively;
• and
• metallization ratios of the first and second divided IDT portions are different from each other in at least one of the first third and fifth IDTs.