An acoustic wave filter includes a first longitudinally coupled resonator including first and second IDT electrodes, and a second longitudinally coupled resonator including third and fourth IDT electrodes. Each IDT electrode includes a wide pitch electrode finger group and a narrow pitch electrode finger group. A number of electrode fingers in the wide pitch electrode finger group of the first IDT electrode is smaller than that in the wide pitch electrode finger group of the second IDT electrode by a percentage equal to or more than about 4.2% and equal to or less than about 23.5%. A number of the electrode fingers in the wide pitch electrode finger group of the IDT electrode third is smaller than that in the wide pitch electrode finger group of the fourth IDT electrode by a percentage equal to or more than about 9.5% and equal to or less than about 52.4%.

A guided acoustic wave device includes a substrate, a lithium tantalate layer on the substrate, and a transducer on the lithium tantalate film. The lithium tantalate has a crystalline orientation defined by (YXl), where is between 10 and 37. The inventors discovered that limiting the crystalline orientation of the lithium tantalate in this manner provides significant increases in the electromechanical coupling coefficient of the acoustic wave device, thereby increasing bandwidth and improving performance.

A multiplexer includes a common terminal, a first band pass filter that is connected to the common terminal and has a first pass band, and a second band pass filter that is connected to the common terminal and has a second pass band located at higher frequencies than the first pass band. The first band pass filter includes an acoustic wave device that includes a support substrate, a piezoelectric body stacked on the support substrate, and an IDT electrode provided on the piezoelectric body. The piezoelectric body is made of lithium niobate. The acoustic wave device utilizes Rayleigh waves.

There is provided a SAW filter manufacturing method for manufacturing a SAW filter from a piezoelectric substrate having planned dividing lines set on a top surface of the piezoelectric substrate, and having a device including comb-shaped electrodes in regions demarcated by the planned dividing lines. The method includes a structure forming step of forming a structure having projections and depressions on an undersurface side of the piezoelectric substrate by irradiating the piezoelectric substrate with a laser beam of a wavelength absorbable by the piezoelectric substrate from the undersurface side of the piezoelectric substrate, and a dividing step of dividing the piezoelectric substrate along the planned dividing lines after the structure forming step.

An acoustic wave filter device includes first and second terminals, an inductor connected to the first terminal, and a longitudinally coupled resonator coupled between the inductor and the second terminal. The longitudinally coupled resonator includes at least one first IDT electrode coupled to the first terminal, and at least one second IDT electrode connected to the second terminal. A total capacitance value of the at least one first IDT electrode is greater than a total capacitance value of the at least one second IDT electrode.

Aspects of this disclosure relate to a filter that includes an acoustic wave device with a multi-layer substrate with heat dissipation. The multi-layer substrate includes a support substrate (e.g., a quartz substrate), a piezoelectric layer, an interdigital transducer electrode on the piezoelectric layer, and a thermally conductive layer configured to dissipate heat associated with the acoustic wave device. The thermally conductive layer is disposed between the support substrate and the piezoelectric layer. The thermally conductive layer has a thickness that is greater than 10 nanometers and less than a thickness of the piezoelectric layer.

A radio-frequency filter (10) includes a series arm circuit (11) and a parallel arm circuit (12). The series arm circuit (11) is disposed on a path connecting an input/output terminal (11m) and an input/output terminal (11n). The parallel arm circuit (12) is connected to a ground and to a node (x1) on the path. The series arm circuit (11) includes a series connecting circuit (11e) and a first variable frequency circuit (11a). The series connecting circuit (11e) includes a series arm resonator (S1) and a capacitor (C1). The first variable frequency circuit (11a) is connected in parallel with the series connecting circuit (11e) and varies the anti-resonant frequency of the series arm circuit (11). The first variable frequency circuit (11a) includes a capacitor (C2) and a switch (SW1) connected in series with each other. The series arm resonator (s1) and the capacitor (C1) are connected in series with each other.

An elastic wave element includes a piezoelectric substrate, an IDT electrode including a first comb-shaped electrode and a second comb-shaped electrode, and reflectors. Each of the reflectors includes a first reflective busbar electrode, a second reflective busbar electrode, and reflective electrode fingers. The first comb-shaped electrode includes a first busbar electrode connected to the first reflective busbar electrodes, and first electrode fingers. The second comb-shaped electrode includes a second busbar electrode and second electrode fingers. In in-between areas, in each of which a reflective electrode finger and a first electrode finger adjacent to each other in the elastic-wave propagation direction face each other, connecting electrodes which electrically couple the reflective electrode fingers to the first electrode fingers are provided.

The present invention discloses a type of ultra-wide band SAW filter which comprises a first SAW resonator group and a second SAW resonator group that are connected to form a ladder structure. Each SAW resonator in the said first SAW resonator group has the same film thickness; each SAW resonator in the said second SAW resonator group has the same film thickness; the film thickness of each SAW resonator in the said first SAW resonator group is the same as or different from the film thickness of each SAW resonator in the said second SAW resonator group. The SAW filter according to the present invention can realize the pass-band non-parasitic mode response and is a high-performance ultra-wide band filter with a bandwidth of 6-20% of the center frequency and an insertion loss of less than 2 dB, and the present invention features small size, low cost and a broad application prospect in the field of military and civilian communications equipment.

A multiplexer includes a common terminal, a first band pass filter that is connected to the common terminal and has a first pass band, and a second band pass filter that is connected to the common terminal and has a second pass band located at higher frequencies than the first pass band. The first band pass filter includes an acoustic wave device that includes a support substrate, a piezoelectric body stacked on the support substrate, and an IDT electrode provided on the piezoelectric body. The piezoelectric body is made of lithium niobate. The acoustic wave device utilizes Rayleigh waves.