Multiplexer

A multiplexer comprising:

• a transmission filter and a reception filter each including a plurality of resonators including one or more series arm resonators;
• wherein
• the transmission filter includes a piezoelectric substrate and a first series arm resonator unit on the piezoelectric substrate;
• the reception filter shares the piezoelectric substrate with the transmission filter and includes a second series arm resonator unit on the piezoelectric substrate;
• the transmission filter includes an input terminal, an output terminal, and a ground terminal, and, in a circuit configuration of the transmission filter, a path connecting the input terminal and the output terminal is a series arm, a path branching from the series arm to the ground terminal is a parallel arm, and a connection point between the series arm and the parallel arm is a node;
• the first series arm resonator unit includes one of the series arm resonators in the transmission filter or a group of a plurality of the series arm resonators in the transmission filter that are connected in series to each other without the node therebetween;
• the reception filter includes an input terminal, an output terminal, and a ground terminal, and, in a circuit configuration of the reception filter, a path connecting the input terminal and the output terminal is a series arm, a path branching from the series arm to the ground terminal is a parallel arm, and a connection point between the series arm and the parallel arm is a node;
• the second series arm resonator unit includes one of the series arm resonators in the reception filter or a group of a plurality of the series arm resonators in the reception filter that are connected in series to each other without the node therebetween;
• on the piezoelectric substrate, among all of the series arm resonators of the transmission filter, one of the series arm resonators in the first series arm resonator unit is located at a shortest distance to all of the resonators of the reception filter;
• on the piezoelectric substrate, among all of the resonators of the reception filter, one of the series arm resonators in the second series arm resonator unit is located at a shortest distance to one of the series arm resonators of the first series arm resonator unit of the transmission filter;
• the series arm resonators of each of the transmission filter and the reception filter each include an IDT electrode, and each of the IDT electrodes includes a plurality of electrode fingers and a crossing region in which, when a direction in which the plurality of electrode fingers extend is defined as an electrode-finger-extending direction, the electrode fingers that are adjacent to each other overlap each other in a direction perpendicular or substantially perpendicular to the electrode-finger-extending direction;
• and
• when a dimension of the crossing region in the electrode-finger-extending direction is defined as a crossing width, the first series arm resonator unit includes a first series arm resonator for which a product of a number of pairs of the plurality of electrode fingers and a crossing width is smallest among all of the series arm resonators of the transmission filter, and the second series arm resonator unit includes a second series arm resonator for which the product of a number of pairs of the plurality of electrode fingers and the crossing width is largest among all of the series arm resonators of the reception filter.