A surface acoustic wave resonator comprises a multi-layer piezoelectric substrate including a carrier substrate, a layer of a first dielectric material disposed on a front side of the carrier substrate, and a layer of piezoelectric material disposed on a front side of the layer of the first dielectric material, the piezoelectric material having a cut angle θ of from about 12 degrees to about 25 degrees to suppress bulk leakage and improve gamma, and interdigital transducer electrodes disposed on a front side of the layer of piezoelectric material.

Disclosed are a resonator and a manufacturing method thereof, a filter, and an electronic device. The resonator includes a substrate, a Bragg reflection layer, and a piezoelectric layer that are sequentially stacked. A first electrode is disposed on a surface that is of the piezoelectric layer and that faces the Bragg reflection layer, a second electrode is disposed on a surface that is of the piezoelectric layer and that is away from the Bragg reflection layer, a border ring is disposed on a surface that is of the second electrode and that is away from the piezoelectric layer, and the resonator has a first resonance region and a second resonance region corresponding to the border ring.

A multiplexer includes a first filter and a second filter with a lower pass band than that of the first filter. A longitudinally coupled acoustic wave resonator of the first filter includes an interdigital transducer electrode group of interdigital transducer electrodes having an asymmetric shape with respect to a center line that passes through a center of the interdigital transducer electrode group and is perpendicular or substantially perpendicular to an acoustic wave propagation direction. The interdigital transducer electrodes connected to a first path on a common terminal side when seen from the longitudinally coupled acoustic wave resonator have a smaller aggregate average of electrode finger pitches of the interdigital transducer electrodes and a smaller sum of numbers of pairs of electrode fingers of the interdigital transducer electrodes, compared with the interdigital transducer electrodes connected to the first path on a first terminal side.

A filter circuit comprises in a signal line a band filter (BF) allowing to let pass a useful frequency band and a notch filter (NF) circuited in series to the band filter for filtering out a stop band frequency. The notch filter comprises a series circuit of a number of parallel shunt elements (SE1 . . . SE6) wherein each shunt element is shifted infrequency against the other shunt elements that the frequencies thereof are distributed (f1 . . . F6) over a notch band. All shunt elements may be realized as a SAW one-port resonator (TR.sub.NF) including regions with different pitches.

A multi-band filter configured to allow signals to pass at multiple frequency bands includes a piezoelectric substrate and a plurality of groups of electrodes disposed on the piezoelectric substrate. Each group forms a respective filter to allow signals to pass at a corresponding frequency band. A first group forms a first filter having a first frequency band and a second group forms a second filter having a second frequency band. The first frequency band is lower than the second frequency band. The filter includes a dielectric film formed to cover at least a part of the piezoelectric substrate and the plurality of groups of electrodes. The filter also includes a passivation film disposed on the dielectric film. The passivation film has a smaller thickness for the first group than for the second group, so as to suppress a spurious response generated in the piezoelectric substrate.

Aspects of this disclosure relate to an acoustic wave filter that includes acoustic wave resonators arranged to filter a radio frequency signal. The acoustic wave resonators include a first acoustic wave resonator. The acoustic wave filter includes a circuit element in parallel with the first acoustic wave resonator in a stage of the acoustic wave filter. The circuit element and the first acoustic wave resonator have different resonant frequencies. The circuit element can reduce an impact of bulk mode of the first acoustic wave resonator on insertion loss of the acoustic wave filter. The first acoustic wave resonator can be a surface acoustic wave resonator in certain embodiments. The circuit element can be a second acoustic wave resonator or a capacitor, for example.

Aspects of this disclosure relate to an acoustic wave filter that includes acoustic wave resonators arranged to filter a radio frequency signal. The acoustic wave resonators include a first acoustic wave resonator. The acoustic wave filter includes a circuit element in parallel with the first acoustic wave resonator in a stage of the acoustic wave filter. The circuit element and the first acoustic wave resonator have different resonant frequencies. The circuit element can reduce an impact of bulk mode of the first acoustic wave resonator on insertion loss of the acoustic wave filter. The first acoustic wave resonator can be a surface acoustic wave resonator in certain embodiments. The circuit element can be a second acoustic wave resonator or a capacitor, for example.

Aspects of this disclosure relate to a multiplexer that includes a first filter and a second filter coupled to a common node. The first filter includes an acoustic filter arranged to filter a radio frequency signal, a matching network coupled between the acoustic filter and the common node, and a parallel circuit coupled in series between the acoustic filter and the common node. The parallel circuit includes an inductive component in parallel with a capacitive component. In certain instances, the first filter is coupled to the common node via a switch, the matching network is coupled to a node between the acoustic filter and the switch, and the parallel circuit is coupled in series between the acoustic filter and the switch. Related methods, radio frequency modules, and wireless communication devices are also disclosed.

Aspects of this disclosure relate to an acoustic wave resonator with transverse mode suppression. The acoustic wave resonator can include a piezoelectric layer, an interdigital transducer electrode, a temperature compensation layer, and a mass loading strip. The mass loading strip can be a conductive strip. The mass loading strip can overlap edge portions of fingers of the interdigital transducer electrode. A layer of the mass loading strip can have a density that is at least as high as a density of a material of the interdigital transducer electrode. The material of the interdigital transducer can impact acoustic properties of the acoustic wave resonator.

A multiplexer includes a common terminal, first and second transmit filters, and a first receive filter connected to the common terminal and each including resonators, a relationship Tx1c < Rx1c < Tx2c is satisfied, where Tx1c, Tx2c, and Rx1c denote center frequencies of pass bands Tx1, Tx2, and Tx3 of the first and second transmit filters and the first receive filter, respectively, a resonator closest to the common terminal in the first receive filter is a series arm resonator, and a pitch ratio denoted by pS1(Rx1)/p(Tx2) is more than about 1 and less than or equal to about 1.035, where p(Tx2) denotes an electrode finger pitch of an IDT electrode in a resonator closest to the common terminal in the second transmit filter and pS1(Rx1) denotes an electrode finger pitch of an IDT electrode of the series arm resonator closest to the common terminal in the first receive filter.