The present disclosure relates to a ladder-type surface acoustic wave (SAW) device, which includes a piezoelectric layer, two reflective structures, at least one series interdigital transducer (IDT) coupled between a first signal point and a second signal point, and at least one shunt IDT. The at least one shunt IDT is coupled at least between the first signal point and ground, or between the second signal point and ground. Herein, the two reflective structures, the at least one series IDT, and the at least one shunt IDT reside over the piezoelectric layer. The at least one series IDT and the at least one shunt IDT are arranged between the two reflective structures.

The present disclosure relates to a ladder-type surface acoustic wave (SAW) device, which includes a piezoelectric layer, two reflective structures, at least one series interdigital transducer (IDT) coupled between a first signal point and a second signal point, and at least one shunt IDT. The at least one shunt IDT is coupled at least between the first signal point and ground, or between the second signal point and ground. Herein, the two reflective structures, the at least one series IDT, and the at least one shunt IDT reside over the piezoelectric layer. The at least one series IDT and the at least one shunt IDT are arranged between the two reflective structures.

A multiplexer (10) includes a common terminal (100c), a filter (21) that supports Band 41, a filter (22) that supports Band 40, and a filter (23) that supports Band 1Rx. A matching circuit (11) includes a capacitor (C1) connected in a path (111), a switch (SW1) connected between a ground and a node in the path (111) between the capacitor (C1) and the filter (21), a resonant circuit connected in a path (112) and having a resonant frequency in Band 40, the resonant frequency being a frequency at which an impedance is minimum, a switch (SW2) connected between the ground and a node in the path (112) between the resonant circuit and the filter (22), an inductor (L1) connected in a path (113), and a switch (SW3) connected between the ground and a node in the path (113) between the inductor (L1) and the filter (23).

A filter includes first and second signal terminals, a filter circuit connected between the first and second signal terminals, a substrate having first and second surfaces, the first and second signal terminals being located on the first surface, a part of the filter circuit being located at a side of the second surface, a line located closer to the first surface than the filter circuit in the substrate, a first end of the line being connected to one of the first and second signal terminals, and a ground terminal that is located on the first surface and to which a second end of the line is connected, an area of a region where the line overlaps with the ground terminal being greater than an area of a region where the line overlaps with the one of the first and second signal terminals when the substrate is viewed in plan view.

An acoustic wave device includes a piezoelectric layer and an interdigital transducer disposed on the piezoelectric layer. The interdigital transducer primarily includes Al and includes an additive selected from a group consisting of Nd, Sc, and Ta, and a concentration of the additive in a region opposite to a piezoelectric-layer-side region of the interdigital transducer is higher than a concentration of the additive in the piezoelectric-layer-side region of the interdigital transducer.

A multiplexer (10) includes a common terminal (100c), a filter (21) that supports Band 41, a filter (22) that supports Band 40, and a filter (23) that supports Band 1Rx. A matching circuit (11) includes a capacitor (C1) connected in a path (111), a switch (SW1) connected between a ground and a node in the path (111) between the capacitor (C1) and the filter (21), a resonant circuit connected in a path (112) and having a resonant frequency in Band 40, the resonant frequency being a frequency at which an impedance is minimum, a switch (SW2) connected between the ground and a node in the path (112) between the resonant circuit and the filter (22), an inductor (L1) connected in a path (113), and a switch (SW3) connected between the ground and a node in the path (113) between the inductor (L1) and the filter (23).

The present disclosure relates to a ladder-type surface acoustic wave (SAW) device, which includes a piezoelectric layer, two reflective structures, at least one series interdigital transducer (IDT) coupled between a first signal point and a second signal point, and at least one shunt IDT. The at least one shunt IDT is coupled at least between the first signal point and ground, or between the second signal point and ground. Herein, the two reflective structures, the at least one series IDT, and the at least one shunt IDT reside over the piezoelectric layer. The at least one series IDT and the at least one shunt IDT are arranged between the two reflective structures.

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.

A radio frequency acoustic filter includes a plurality of resonators arranged to filter a signal. At least one resonator of the plurality of resonators includes a support substrate, a functional layer, and a piezoelectric layer. Both the piezoelectric layer and the functional layer are supported by the support substrate. An interdigital transducer structure is at least partially formed in the piezoelectric layer.

A filter includes first and second signal terminals, a filter circuit connected between the first and second signal terminals, a substrate having first and second surfaces, the first and second signal terminals being located on the first surface, a part of the filter circuit being located at a side of the second surface, a line located closer to the first surface than the filter circuit in the substrate, a first end of the line being connected to one of the first and second signal terminals, and a ground terminal that is located on the first surface and to which a second end of the line is connected, an area of a region where the line overlaps with the ground terminal being greater than an area of a region where the line overlaps with the one of the first and second signal terminals when the substrate is viewed in plan view.