Elastic wave filter, branching filter, and communication device

An elastic wave filter comprising:

• a piezoelectric substrate;
• a first terminal;
• a second terminal;
• and
• a filter body that is provided on the piezoelectric substrate and in which a series arm including a plurality of series resonators connected in series with one another between the first terminal and the second terminal and a plurality of parallel resonators are connected in a ladder form,
• wherein
• the series arm has
• a first split arm that extends from one side to an other side in a predetermined direction with respect to the piezoelectric substrate and includes at least one of the series resonators,
• a second split arm that extends from a part of the first split arm on the other side toward the one side and includes at least one of the series resonators, and
• regions extended along a straight line parallel with an elastic wave propagation direction from a series resonator located closest to the first terminal from a circuit perspective among the plurality of series resonators and a parallel resonator located closest to the first terminal from a circuit perspective among the plurality of parallel resonators do not overlap a series resonator located closest to the second terminal from a circuit perspective among the plurality of series resonators and a parallel resonator located closest to the second terminal from a circuit perspective among the plurality of parallel resonators,
• wherein a length, in a direction orthogonal to the elastic wave propagation direction, of a region of the piezoelectric substrate where the filter body is located is equal to or less than a length combining a sum of lengths of the plurality of series resonators in the direction orthogonal to the elastic wave propagation direction and a sum of lengths of the plurality of parallel resonators in the direction orthogonal to the elastic wave propagation direction.

A branching filter comprising:

• an antenna terminal;
• a transmission filter connected to the antenna terminal;
• a reception filter connected to the antenna terminal;
• an elastic wave filter comprising:
• a piezoelectric substrate;
• a first terminal;
• a second terminal;
• and
• a filter body that is provided on the piezoelectric substrate and in which a series arm including a plurality of series resonators connected in series with one another between the first terminal and the second terminal and a plurality of parallel resonators are connected in a ladder form,
• wherein
• the series arm has
• a first split arm that extends from one side to an other side in a predetermined direction with respect to the piezoelectric substrate and includes at least one of the series resonators, and
• a second split arm that extends from a part of the first split arm on the other side toward the one side and includes at least one of the series resonators, and
• regions extended along a straight line parallel with an elastic wave propagation direction from a series resonator located closest to the first terminal from a circuit perspective among the plurality of series resonators and a parallel resonator located closest to the first terminal from a circuit perspective among the plurality of parallel resonators do not overlap a series resonator located closest to the second terminal from a circuit perspective among the plurality of series resonators and a parallel resonator located closest to the second terminal from a circuit perspective among the plurality of parallel resonators,
• wherein
• only the reception filter of the transmission filter and the reception filter is the elastic wave filter;
• the transmission filter shares the piezoelectric substrate with the reception filter and has electrodes located on the piezoelectric substrate;
• and
• an area of a region where the filter body is located on the piezoelectric substrate is equal to or less than a half of an area of a region where the electrodes are located.