Abstract: In a composite filter device, a first acoustic wave resonator includes a functional electrode on a first main surface of a first piezoelectric substrate, and a wiring electrode is on the first main surface and is not connected to a signal potential. A support is on the first main surface and surrounds the first acoustic wave resonator. A second piezoelectric substrate is on the support and includes a third main surface closer to the support than a fourth main surface. A second acoustic wave resonator includes a functional electrode on the third main surface. The second acoustic wave resonator is a parallel-arm resonator higher in resonant frequency than any other parallel-arm resonator or a series-arm resonator lower in resonant frequency than any other series-arm resonator. The second acoustic wave resonator and the wiring electrode overlap each other when viewed in plan.

Abstract: An acoustic wave device includes a support substrate, a piezoelectric layer on the support substrate, and a functional element on the piezoelectric layer. The support substrate and the piezoelectric layer each have a rectangular or substantially rectangular shape in plan view from a direction normal to the support substrate. At least one corner portion of the piezoelectric layer has a curved shape or a polygonal shape.

Abstract: A ladder filter includes series arm resonators, parallel arm resonators, and first and second inductors. Second ends of the parallel arm resonators are connected in common to each other and are connected to a ground potential. A first end of each of the first and second inductors is connected to a series arm, and second ends thereof are connected in common to each other and are connected to the ground potential with a capacitor therebetween.

Abstract: An acoustic wave device includes first and second acoustic wave resonator units. In a first IDT electrode of the first acoustic wave resonator unit, an intersecting width region includes a central region and first and second low acoustic velocity regions at outer side portions of the central region. The first and second high acoustic velocity regions include openings along an acoustic wave propagation direction. In the second acoustic wave resonator unit, a second IDT electrode includes a central region and first and second low acoustic velocity regions at outer side portions in an intersecting width direction of the central region. At an outer side portion of the first low acoustic velocity region, openings are at a third busbar. At an outer side portion of the second low acoustic velocity region, openings are not provided for a fourth busbar.

Abstract: An acoustic wave element includes a piezoelectric film, an interdigital transducer electrode on a first principal surface of the piezoelectric film, and a high acoustic velocity member near a second principal surface of the piezoelectric film. A surface of the high acoustic velocity member opposite to the piezoelectric film and a side surface of each of the high acoustic velocity member and the piezoelectric film are covered with resin. At least a portion of the side surface of the high acoustic velocity member is in contact with the resin. A gap is provided between the resin and at least a portion of the side surface of the piezoelectric film.

Abstract: Of a plurality of acoustic wave resonators, the acoustic wave resonator electrically closest to a first terminal is an antenna end resonator, the antenna end resonator is a first acoustic wave resonator and at least one acoustic wave resonator other than the antenna end resonator of the plurality of acoustic wave resonators is a second acoustic wave resonator. An acoustic wave device satisfies a first condition. The first condition is a condition that a high acoustic velocity layer of the first acoustic wave resonator and a high acoustic velocity layer of the second acoustic wave resonator each include a silicon substrate, a surface closer to a piezoelectric layer in the silicon substrate of the first acoustic wave resonator is a plane or a plane, and a surface closer to a piezoelectric layer in the silicon substrate of the second acoustic wave resonator is a plane.

Abstract: In a multiplexer, input or output terminals of four acoustic wave filters are connected to, among a plurality of terminals provided on piezoelectric substrates, antenna terminals connected to an antenna connection terminal; the four acoustic wave filters include a first acoustic wave filter and a second acoustic wave filter that is located at a farther position from the antenna connection terminal than a position of the first acoustic wave filter in a plan view of a substrate; and among the plurality of terminals, the terminals located at the closest position to the antenna connection terminal in the plan view of the substrate are connected to the second acoustic wave filter as the antenna terminals.

Abstract: In a multiplexer, input or output terminals of four acoustic wave filters are connected to, among a plurality of terminals provided on piezoelectric substrates, antenna terminals connected to an antenna connection terminal; the four acoustic wave filters include a first acoustic wave filter and a second acoustic wave filter that is located at a farther position from the antenna connection terminal than a position of the first acoustic wave filter in a plan view of a substrate; and among the plurality of terminals, the terminals located at the closest position to the antenna connection terminal in the plan view of the substrate are connected to the second acoustic wave filter as the antenna terminals.

Abstract: A multiplexer includes a common terminal, a reception terminal, and transmission terminals; a reception filter between the common terminal and the reception terminal; a transmission filter between the common terminal and the transmission terminal; a transmission filter between the common terminal and the transmission terminal; a first inductor connected in series between the common terminal and the reception filter; a second inductor connected between the transmission terminal and the transmission filter; and a third inductor connected between the transmission terminal and the transmission filter. The first inductor and the second inductor couple with each other through a magnetic field, and the first inductor and the third inductor couple with each other through a magnetic field.

Abstract: In a splitter, a first band pass filter is connected between an antenna terminal and a first terminal, a high pass filter and a second band pass filter are connected between the antenna terminal and a second terminal, a pass band of the second band pass filter is higher than a pass band of the first band pass filter, a cut off frequency of the high pass filter is located closer to the high-frequency side than the pass band of the first band pass filter, the pass band of the second band pass filter is located closer to the high-frequency side than the cut off frequency, and the high pass filter also functions as a notch filter having an anti-resonant frequency in a transition region such that the steepness of the transition region between the pass band of the second band pass filter and the attenuated band is high.

Abstract: A multiplexer includes a common terminal, a reception terminal, and transmission terminals; a reception filter between the common terminal and the reception terminal; a transmission filter between the common terminal and the transmission terminal; a transmission filter between the common terminal and the transmission terminal; a first inductor connected in series between the common terminal and the reception filter; a second inductor connected between the transmission terminal and the transmission filter; and a third inductor connected between the transmission terminal and the transmission filter. The first inductor and the second inductor couple with each other through a magnetic field, and the first inductor and the third inductor couple with each other through a magnetic field.

Abstract: An elastic wave filter device has a center frequency of a reception frequency band. A plurality of parallel arms are connected to a portion of a series arm on a second signal terminal side of a portion in which a first series-arm resonator is provided. Series-arm resonators among the plurality of series-arm resonators other than the first series-arm resonator include a series-arm resonator having a resonant frequency higher than the resonant frequency of the first series-arm resonator. The resonant frequency of the first series-arm resonator is equal to the reception frequency band.

Abstract: In a splitter, a first band pass filter is connected between an antenna terminal and a first terminal, a high pass filter and a second band pass filter are connected between the antenna terminal and a second terminal, a pass band of the second band pass filter is higher than a pass band of the first band pass filter, a cut off frequency of the high pass filter is located closer to the high-frequency side than the pass band of the first band pass filter, the pass band of the second band pass filter is located closer to the high-frequency side than the cut off frequency, and the high pass filter also functions as a notch filter having an anti-resonant frequency in a transition region such that the steepness of the transition region between the pass band of the second band pass filter and the attenuated band is high.

Abstract: An elastic wave filter device has a center frequency of a reception frequency band. A plurality of parallel arms are connected to a portion of a series arm on a second signal terminal side of a portion in which a first series-arm resonator is provided. Series-arm resonators among the plurality of series-arm resonators other than the first series-arm resonator include a series-arm resonator having a resonant frequency higher than the resonant frequency of the first series-arm resonator. The resonant frequency of the first series-arm resonator is equal to the reception frequency band.