An acoustic resonator includes a piezoelectric plate with a back surface attached to a substrate. An interdigital transducer (IDT) including interleaved fingers is formed on the front surface of the piezoelectric plate, the IDT comprising multiple copies of a unit cell juxtaposed along a length of the IDT. Each unit cell includes a first pitch/mark zone having a first pitch P1 between adjacent fingers and a first mark M1 and a second pitch/mark zone having a second pitch P2 and a second mark M2, where P.sub.2 is not equal to P.sub.1 and M.sub.2 is not equal to M.sub.1. A radio frequency signal applied to the IDT causes the first pitch mark zone and the second pitch/mark zone to excite a same shear primary acoustic mode in the piezoelectric plate.

Aspects of this disclosure relate to an acoustic wave resonator having at least two resonant frequencies. An acoustic wave filter can include series acoustic wave resonators and shunt acoustic wave resonators together arranged to filter a radio frequency signal. A first shunt resonator of the shunt acoustic wave resonators can include an interdigital transducer electrode and have at least a first resonant frequency and a second resonant frequency. Related acoustic wave resonators, multiplexers, wireless devices, and methods are disclosed.

A transducer structure for a surface acoustic wave device, comprising a pair of inter-digitated comb electrodes, wherein the pair of inter-digitated comb electrodes comprises neighboring electrode means belonging to different comb electrodes and having a pitch p being defined as the edge-to-edge electrode means distance between two neighboring electrode means, the pitch p satisfying the Bragg condition; characterized in that the pair of inter-digitated comb electrodes comprises at least one region in which two or more neighboring electrode means belong to the same comb electrode while having an edge-to-edge distance to each other corresponding to the pitch p. The present disclosure relates also to a surface acoustic wave filter device.

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 multiplexer includes a transmission-side filter connected to a common terminal and a transmission input terminal, and a reception-side filter connected to the common terminal and a reception output terminal, in which the transmission-side filter includes serial arm resonators, parallel arm resonators, and a parallel arm circuit. In an interdigital transducer electrode included in the serial arm resonator connected closest to the common terminal, an electrode finger pitch at a center portion in an arrangement direction of electrode fingers is maximum among electrode finger pitches of the interdigital transducer electrode, and electrode finger pitches at end portions in the arrangement direction are minimum among the electrode finger pitches of the interdigital transducer electrode.

Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. A pitch between adjacent fingers of the IDT is varied along one or both of an aperture of the IDT and a length of the IDT.

A surface acoustic wave resonator comprises interdigital transducer (IDT) electrodes disposed on an upper surface of a piezoelectric substrate between first and second reflector gratings each including reflector electrodes. The IDT electrodes include a central region having a first width in a direction perpendicular to an extension direction of the IDT electrodes and edge regions each having a second width on opposite sides of the central region. The IDT electrodes have a lesser average pitch in the central region than an average pitch of the IDT electrodes in each of the edge regions. The reflector electrodes have a lesser average pitch than the average pitch of the IDT electrodes in the central region.

Reduced-size guided-surface acoustic wave (SAW) resonators are disclosed. Guided-SAW resonators can achieve high acoustic coupling and acoustic quality Q, but may have a larger surface area compared with a traditional temperature compensated (TC)-SAW resonator. In an exemplary aspect, a guided-SAW device is fabricated with a metal-insulator-metal (MIM) capacitor to produce a guided-SAW which has the same high Q with a surface area which is the same or less than traditional TC-SAW resonators.

A band elimination filter includes a plurality of parallel resonators, each including a piezoelectric substrate and an IDT electrode on a surface of the piezoelectric substrate. The IDT electrode includes a pair of comb-shaped electrodes opposing each other, and the IDT electrode includes electrode fingers, a pitch of the electrode fingers being different between an end portion of the IDT electrode in a propagation direction of an elastic wave and a central portion of the IDT electrode different from the end portion.

Aspects of this disclosure relate to an acoustic wave resonator having at least two resonant frequencies. An acoustic wave filter can include series acoustic wave resonators and shunt acoustic wave resonators together arranged to filter a radio frequency signal. A first shunt resonator of the shunt acoustic wave resonators can include an interdigital transducer electrode and have at least a first resonant frequency and a second resonant frequency. Related acoustic wave resonators, multiplexers, wireless devices, and methods are disclosed.