A filter circuit includes a first inductor circuit connected in series with a second inductor circuit, and a first capacitor circuit connected in series with a second capacitor circuit. The first inductor circuit and the second inductor circuit are connected between a first input/output port and a second input/output port of the filter circuit. A third inductor circuit is connected between a reference node and a first node that is between the first inductor circuit and the second inductor circuit. A resonator circuit is connected to a second node between the first capacitor circuit and the second capacitor circuit. A fourth inductor circuit is connected between the resonator circuit and the reference node. In some embodiments, another resonator circuit is connected between the input port and the output port of the filter circuit.

An acoustic wave device comprises a substrate including a piezoelectric material, interdigital transducer (IDT) electrodes disposed on a surface of the substrate, a first dielectric film having a lower surface disposed on the IDT electrodes and the surface of the substrate, first strips formed of a first material having a density greater than a density of the first dielectric film disposed within the first dielectric film over tips of the interdigitated electrode fingers in the edge regions of the IDT electrodes, and second strips formed of a second material having a density greater than the density of the first dielectric film disposed within the first dielectric film in the gap regions of the IDT electrodes, laterally spaced from the first strips in a direction perpendicular to a direction of propagation of a main acoustic wave through the acoustic wave device, and extending only partially over the gap regions.

An RF ladder filter having a parallel capacitance compensation circuit is disclosed. The parallel capacitance compensation circuit is made up of a first inductive element with a first T-terminal and a first end coupled to a first ladder terminal and a second inductive element with a second T-terminal that is coupled to the first T-terminal of the first inductive element and a second end coupled to a second ladder terminal. Further included is a compensating acoustic RF resonator (ARFR) having a fixed node terminal and a third T-terminal that is coupled to the first T-terminal of the first inductive element and the second T-terminal of the second inductive element, and a finite number of series-coupled ladder ARFRs, wherein the parallel capacitance compensation circuit is coupled across one of the finite number of series-coupled ARFRs by way of the first ladder terminal and the second ladder terminal.

An elastic wave device includes a piezoelectric thin film, IDT electrodes on the piezoelectric thin film, an insulating layer surrounding the piezoelectric thin film on a primary surface of a support substrate, a spacer layer surrounding the piezoelectric thin film in plan view, and a cover on the spacer layer. The spacer layer includes an outer edge and an inner edge closer than the outer edge to the piezoelectric thin film in plan view. The primary surface of the insulating layer closer to the spacer layer includes a sloping region that extends where the insulating layer overlaps the spacer layer in plan view and in which the distance from the first primary surface of the support substrate along the direction perpendicular or substantially perpendicular to the support substrate increases from the outer edge toward the inner edge.

An acoustic wave device comprises a substrate including a piezoelectric material, and interdigital transducer (IDT) electrodes disposed on a surface of the substrate. The IDT electrodes have gap regions, edge regions, and center regions. A maximum width of the IDT electrodes in the gap regions is greater than the maximum width of the IDT electrodes in the edge regions, thereby achieving a velocity of an acoustic wave in the gap regions being greater than the velocity of the acoustic wave in the center regions, and the velocity of the acoustic wave in the center regions being greater than the velocity of the acoustic wave in the edge regions.

Communications devices, triplexers, high-pass filters, and low-pass filters are disclosed. A communications device includes a triplexer having a common port and first, second, and third branch ports. A hybrid LC/SAW high-pass filter is connected between the common port and the third branch port, a hybrid LC/SAW low-pass filter is connected between the common port and an internal node, an LC high-pass filter is connected between the internal node and the second branch port, and an LC low-pass filter is connected between the internal node and the first branch port.

A composite filter device includes a first filter and a plurality of second filters with different passbands. End portions of the first filter and the plurality of second filters are connected to a common connection. The first filter includes a piezoelectric substrate made of LiNbO.sub.3, an IDT electrode provided on the piezoelectric substrate, and a dielectric layer provided on the piezoelectric substrate so as to cover the IDT electrode. The first filter utilizes a fundamental wave of Rayleigh waves. The passband of the first filter is arranged in a frequency band that is lower than any of the passbands of the plurality of second filters.

A first filter of a multiplexer includes a ladder filter structure with a plurality of series resonators and a plurality of parallel resonators. Each resonator is an acoustic wave resonator that includes an InterDigital Transducer (IDT) electrode including a pair of comb-shaped electrodes. A total number of reflection electrode fingers of the reflectors of at least one of the series resonator that is closest to the common terminal among the series resonators and the parallel resonator that is closest to the common terminal is smaller than a total number of reflection electrode fingers of the reflectors of each of a remainder of the resonators.

An apparatus is disclosed for site-selective piezoelectric-layer trimming. The apparatus includes at least one surface-acoustic-wave filter with an electrode structure and a piezoelectric layer. The electrode structure has multiple gaps. The piezoelectric layer has a planar surface defined by a first (X) axis and a second (Y) axis that is perpendicular to the first (X) axis. The piezoelectric layer is configured to propagate an acoustic wave along the first (X) axis. The piezoelectric layer includes a first portion that supports the electrode structure and a second portion that is exposed by the multiple gaps of the electrode structure. The second portion has different heights across the second (Y) axis. The different heights are defined with respect to a third (Z) axis that is substantially normal to the planar surface.

An acoustic wave resonator includes: a piezoelectric substrate; an IDT located on the piezoelectric substrate and including comb-shaped electrodes facing each other, each of the comb-shaped electrodes including: electrode fingers exciting an acoustic wave; and a bus bar to which the electrode fingers are connected; a dielectric film located on the piezoelectric substrate in an overlap region, where the electrode fingers of one of the comb-shaped electrodes and the electrode fingers of the other overlap, so as to cover the electrode fingers; and an additional film located on the dielectric film in the overlap region and having a density greater than that of the dielectric film, and of which a film thickness in edge regions corresponding to both edges of the overlap region in an extension direction of the electrode fingers is greater than a film thickness in a central region sandwiched between the edge regions in the overlap region.