Acoustic wave filter

An acoustic wave filter comprising:

• a plurality of input-output terminals;
• a filter circuit in a first path linking the plurality of input-output terminals;
• and
• an additional circuit in a second path connected in parallel to at least a portion of the first path;
• wherein
• the additional circuit includes a resonator including a plurality of interdigital transducers (IDTs) and a reflector;
• the plurality of IDTs are arranged along a first direction;
• the IDTs each include a plurality of electrode fingers extending in a second direction intersecting with the first direction and arranged along the first direction;
• the reflector is adjacent to an outermost IDT that is located in an outermost side portion of the plurality of IDTs with respect to the first direction and includes a plurality of reflection electrode fingers extending in the second direction and arranged along the first direction;
• the outermost IDT includes a first excitation portion and a second excitation portion;
• the first excitation portion is adjacent to the reflector in the first direction;
• the outermost IDT includes ((N/2)+1) electrode fingers when a total number N of the electrode fingers included in the outermost IDT is an even number, or the outermost IDT includes ((N+1)/2) electrode fingers when the total number N is an odd number;
• the second excitation portion is on an opposite side to the reflector as seen from the first excitation portion in the first direction and includes two or more electrode fingers, except the electrode fingers of the first excitation portion, among the plurality of electrode fingers included in the outermost IDT;
• and
• assuming an average arrangement pitch of the electrode fingers included in the first excitation portion in the first direction is px and an average arrangement pitch of the plurality of reflection electrode fingers in the first direction is pr, pr/px has a value in a range from about 0.5 to about 0.97 or a range from about 1.15 to about 2.0.