An acoustic wave device includes a piezoelectric layer made of lithium niobate or lithium tantalate, and first and second electrodes opposed to each other in a direction that intersects with a thickness direction of the piezoelectric layer. The first and second electrodes are adjacent electrodes, and, when a thickness of the piezoelectric layer is d and a distance between centers of the first and second electrodes is p, d/p is less than or equal to about 0.5.

An acoustic wave device includes a piezoelectric substrate, a first interdigital transducer (IDT) electrode, reflectors on both sides of the first IDT electrode in a propagation direction of an acoustic wave, and a second IDT electrode facing the first IDT electrode with a reflector interposed therebetween. The first and second IDT electrodes include first and second intersecting areas in which electrode fingers overlap in the propagation direction. The first and second intersecting areas overlap in the propagation direction. A third busbar of the second IDT electrode is coupled to a first busbar of the first IDT electrode. A fourth busbar of the second IDT electrode is coupled to a ground potential. A resonant frequency of the second IDT electrode is in a frequency band of an interference wave signal.

A Lamb wave resonator includes a piezoelectric material layer, a first finger electrode, a second finger electrode, at least two floating electrodes, and at least two gaps. The first finger electrode is disposed on one side of the piezoelectric material layer and includes a first main portion and first fingers. The second finger electrode is disposed on the side of the piezoelectric material layer and includes a second main portion and second fingers. The first fingers are parallel to and alternately arranged with the second fingers. The floating electrodes are disposed between each first finger and each second finger, and the gaps are disposed at two ends of each floating electrode, respectively.

Disclosed are a resonant device and an acoustic filter. The resonant device includes a wafer substrate, a piezoelectric layer and an interdigital electrode layer. The piezoelectric layer is located on a side of the wafer substrate and includes a piezoelectric monocrystal material, and the piezoelectric monocrystal material includes a first crystal axis, a second crystal axis and a third crystal axis perpendicular to each other. A direction of an electric field generated by the interdigital electrode layer in the piezoelectric layer is a device direction.

In some embodiments, a surface acoustic wave device can include a piezoelectric substrate and an interdigital transducer electrode implemented on a surface of the piezoelectric substrate, such that the surface acoustic device supports a surface acoustic wave having a wavelength λ and a phase velocity less than 3,000 m/s with an electromechanical coupling coefficient of at least 9.0. In some embodiments, the phase velocity less than 2,000 m/s, and the surface acoustic wave can include a lowest asymmetry (A0) mode. In some embodiments, such a surface acoustic wave device can be implemented in products such as a radio-frequency filter, a radio-frequency module and a wireless device.

A receiving filter includes a reception terminal which outputs reception signals from an antenna terminal, a second DMS filter configured by a longitudinally coupled double-mode type acoustic wave filter which is located in a signal path from the antenna terminal to the reception terminal, a fourth GND terminal given a reference potential, and a fourth GND wiring connected to the fourth GND terminal and to the second DMS filter. A reception terminal conductor configured by the reception terminal and the reception terminal wiring connected to the reception terminal and A fourth GND conductor configured by the fourth GND terminal and the fourth GND wiring are adjacent and are capacity-coupled with respect to each other.

A resonator is provided that includes a piezoelectric layer having a first and second surfaces that oppose each other, an IDT electrode on the first surface of the piezoelectric layer, and a high acoustic velocity substrate on the second surface of the piezoelectric layer. The piezoelectric layer is made from a quartz crystal having cut-angles obtained by rotating a plane orthogonal to a crystal Y-axis about a crystal X-axis, in a propagation direction at 90°±10° to the crystal X-axis of the piezoelectric layer, an acoustic velocity in the high acoustic velocity substrate is higher than an acoustic velocity in the piezoelectric layer, and the IDT electrode includes a comb-shaped electrode including multiple electrode fingers aligned in the propagation direction.

A multiplexer includes first and second nodes, an inductor, a first transmit/receive filter, and second and third transmit filters. The inductor is connected at one end to the first node and at the other end to the second node. The first transmit/receive filter is connected to the first node without the inductor interposed therebetween and uses the transmit and receive bands of band A as a pass band. The second transmit filter is connected to the second node and uses the transmit band of band B as a pass band. The third transmit filter is connected to the second node and uses the transmit band of band C as a pass band.

A filter device includes a filter between an input terminal and an output terminal, and an additional circuit connected in parallel with the filter between the input terminal and the output terminal. The additional circuit includes at least two longitudinally coupled resonators connected in parallel with each other and including longitudinally coupled resonators, and at least one capacitance element between the input terminal and the at least two longitudinally coupled resonators or between the output terminal and the at least two longitudinally coupled resonators. The average pitch of a plurality of electrode fingers of IDT electrodes of the longitudinally coupled resonator and the average pitch of a plurality of electrode fingers of IDT electrodes of the longitudinally coupled resonator are different from each other.

A resonator includes an interdigital transducer provided with a main electrode area formed to a shape of a comb on a piezoelectric substrate by a reference pitch in such a manner as to have a unit length along a longitudinal direction thereof and one pair of first electrode areas constituted of one side first electrode area formed to a shape of a comb on the piezoelectric substrate by a first increment pitch obtained by increasing the reference pitch by a first value in such a manner as to have the unit length along the longitudinal direction and the other side first electrode area formed to a shape of a comb on the piezoelectric substrate by a first decrement pitch obtained by decreasing the reference pitch by almost the same value as the first value.