Longitudinally coupled resonator acoustic wave filter

A longitudinally coupled resonator acoustic wave filter comprising:

• a piezoelectric substrate;
• a first IDT electrode on the piezoelectric substrate;
• and
• a second IDT electrode on the piezoelectric substrate and adjacent to the first IDT electrode;
• wherein
• the first IDT electrode includes a hot-side busbar connected to a hot-side potential, a ground-side busbar connected to a ground-side potential, a plurality of first electrode fingers connected to the hot-side busbar, and a plurality of second electrode fingers connected to the ground-side busbar;
• the second IDT electrode includes a hot-side busbar connected to a hot-side potential, a ground-side busbar connected to a ground-side potential, a plurality of third electrode fingers connected to the hot-side busbar, and a plurality of fourth electrode fingers connected to the ground-side busbar;
• when a direction in which the first to fourth electrode fingers extend is a first direction, a direction perpendicular or substantially perpendicular to the first direction is a second direction, and a region in which the plurality of first electrode fingers and the plurality of second electrode fingers of the first IDT electrode overlap each other in the second direction is an interdigitated region of the first IDT electrode and a region in which the plurality of third electrode fingers and the plurality of fourth electrode fingers of the second IDT electrode overlap each other in the second direction is an interdigitated region of the second IDT electrode, the ground-side busbar of the first IDT electrode and the hot-side busbar of the second IDT electrode face each other in the second direction, the hot-side busbar of the first IDT electrode and the ground-side busbar of the second IDT electrode face each other in the second direction, and a projecting portion extending in the second direction toward the second IDT electrode beyond the interdigitated region of the first IDT electrode is provided, the projecting portion being connected to the ground-side busbar of the first IDT electrode;
• and
• a width in the first direction of the hot-side busbar of the second IDT electrode tapers from a middle of the hot-side busbar of the second IDT electrode toward both ends in the second direction of the hot-side busbar of the second IDT electrode.

A longitudinally coupled resonator acoustic wave filter comprising:

• a piezoelectric substrate;
• a first IDT electrode on the piezoelectric substrate;
• and
• a second IDT electrode on the piezoelectric substrate and adjacent to the first IDT electrode;
• wherein
• the first IDT electrode includes a hot-side busbar connected to a hot-side potential, a ground-side busbar connected to a ground-side potential, a plurality of first electrode fingers connected to the hot-side busbar, and a plurality of second electrode fingers connected to the ground-side busbar;
• the second IDT electrode includes a hot-side busbar connected to a hot-side potential, a ground-side busbar connected to a ground-side potential, a plurality of third electrode fingers connected to the hot-side busbar, and a plurality of fourth electrode fingers connected to the ground-side busbar;
• when a direction in which the first to fourth electrode fingers extend is a first direction, a direction perpendicular or substantially perpendicular to the first direction is a second direction, and a region in which the plurality of first electrode fingers and the plurality of second electrode fingers of the first IDT electrode overlap each other in the second direction is an interdigitated region of the first IDT electrode and a region in which the plurality of third electrode fingers and the plurality of fourth electrode fingers of the second IDT electrode overlap each other in the second direction is an interdigitated region of the second IDT electrode, the ground-side busbar of the first IDT electrode and the hot-side busbar of the second IDT electrode face each other in the second direction, the hot-side busbar of the first IDT electrode and the ground-side busbar of the second IDT electrode face each other in the second direction, and a projecting portion extending in the second direction toward the second IDT electrode beyond the interdigitated region of the first IDT electrode is provided, the projecting portion being connected to the ground-side busbar of the first IDT electrode;
• and
• when a distance between an end portion of the projecting portion, the end portion being adjacent to the interdigitated region of the second IDT electrode, and an edge to which the plurality of third electrode fingers of the hot-side busbar of the second IDT electrode are connected is d1 and a distance between the hot-side busbar of the second IDT electrode and the ground-side busbar of the second IDT electrode is d2, d1<d2 is satisfied.