A transmit filter circuit includes an input terminal, an output terminal, plural series arm resonators, and a parallel arm resonator. The input terminal receives a transmit signal. The output terminal is electrically connected to an antenna. The plural series arm resonators are electrically connected in series with each other on a line between the input and output terminals. The plural series arm resonators include first and second series arm resonators. The first series arm resonator is closest to the output terminal. The second series arm resonator is second closest to the output terminal. A first end of the parallel arm resonator is electrically connected to a node between the first and second series arm resonators. A reference potential is provided to a second end of the parallel arm resonator. The resonant frequency of the first series arm resonator is higher than that of the second series arm resonator.

Certain aspects of the present disclosure can be implemented in an electroacoustic device. The electroacoustic device generally includes a substrate and one or more resonator structures disposed above the substrate. In some cases, each resonator structure of the one or more resonator structures includes a bulk acoustic resonator, an acoustic mirror disposed below the bulk acoustic resonator, and one or more porous material layers disposed below the acoustic mirror and above the substrate.

An apparatus is disclosed for harmonic reduction with filtering. In example aspects, the apparatus includes a filter circuit with first and second filter ports, first and second lattice filters, and first and second signal manipulator circuits. The first signal manipulator circuit includes a first port, a second port, and a third port coupled to the first filter port. The first signal manipulator circuit splits an input signal into multiple split signals, shifts a phase thereof to produce at least one phase-shifted split signal, and provides the phase-shifted split signal to the first and second ports. The first lattice filter is coupled to the first port, and the second lattice filter is coupled to the second port. The second signal manipulator circuit includes a first port coupled to the first lattice filter, a second port coupled to the second lattice filter, and a third port coupled to the second filter port.

A method of plugging a hydrocarbon well includes deploying a downhole tool to remove at least a portion of a casing at a section of well to be plugged. Deploying a blocking device downhole to block a bottom of the section of well to be plugged. Deploying a plugging material downhole onto the blocking device to fill an area to be plugged. Deploying an exothermic fluid downhole, wherein activation of the exothermic material liquefies the plugging material. Allowing the plugging material and the exothermic fluid to solidify form a cast-in-place plug that fills the section of well to be plugged.

Embodiments of this disclosure relate to bulk acoustic wave resonators on a substrate. The bulk acoustic wave resonators include a first bulk acoustic wave resonator, a second bulk acoustic wave resonator, a conductor electrically connecting the first bulk acoustic wave resonator to the second bulk acoustic wave resonator, and an air gap positioned between the conductor and a surface of the substrate.

An acoustic wave filter device includes a second filter section connected to a first filter section. The second filter section includes acoustic wave resonators in a ladder circuit configuration. Of the acoustic wave resonators in the first and second filter sections, the acoustic wave resonator having the smallest fractional bandwidth is included in the second filter section. In the second filter section, inductors are respectively connected between parallel arm resonators and a reference potential. Attenuation near a pass band in the second filter section is larger than attenuation near a pass band in the first filter section.

A bulk acoustic resonator package includes a substrate, a cap, and first and second bulk acoustic resonators each including a first electrode, a piezoelectric layer, and a second electrode stacked in a direction in which the substrate and the cap face each other, and disposed between the substrate and the cap, wherein the first and second bulk acoustic resonators form a bandwidth based on first and second resonant frequencies different from each other and first and second antiresonant frequencies different from each other, a difference between the first and second resonant frequencies exceeds 200 MHz, the first bulk acoustic resonator is disposed closer to the substrate than to the cap, and the second bulk acoustic resonator is disposed closer to the cap than to the substrate.

A bulk acoustic wave (BAW) resonator comprises: a first electrode; a second electrode comprising a plurality of sides, wherein at least one of the sides is a connection side; a piezoelectric layer disposed between the first and second electrodes, and an acoustic reflective element disposed beneath the first electrode, the second electrode and the piezoelectric layer, wherein an overlap of the reflective element, the first electrode, the second electrode, and the piezoelectric layer defines an active area of the acoustic resonator; a bridge adjacent to a termination of the active area of the BAW resonator; and a discontinuity disposed in the bridge.

A filter includes: one or more series resonators that are connected in series between an input terminal and an output terminal; one or more parallel resonators that are connected in parallel between the input terminal and the output terminal; and a laterally coupled resonator that is connected in parallel with at least one of the one or more series resonators.

Aspects of this disclosure relate to an acoustic wave device with a plurality of piezoelectric layers positioned laterally relative to each other between two electrodes. One of the piezoelectric layers has a different property than another of the piezoelectric layers. Examples of the different property include c-axis orientation, doping concentration, dopant material, and piezoelectric material. At least part of each of the piezoelectric layers can be in a main acoustically active region of the acoustic wave device.