An acoustic wave resonator includes: a first piezoelectric portion of a piezoelectric layer, disposed on a cavity and having a first average thickness; and a second piezoelectric portion of the piezoelectric layer, disposed adjacent to an edge of the first piezoelectric portion and having a second average thickness that is different from the first average thickness.

A filter includes a plurality of series portions each including one or more series resonators, and a plurality of shunt portions each including one or more shunt resonators. At least one of the plurality of shunt portions includes two shunt resonators connected to each other in anti-series, and antiresonance frequencies of the two shunt resonators are arranged externally of a passband.

A composite filter device includes a connection portion connected to a common terminal, a first filter between the connection portion and a first terminal, a second filter between the connection portion and a second terminal, a first inductor that is connected in series between the second filter and the connection portion, includes a first wiring electrode wound in a predetermined direction, and is provided at an internal layer of a multilayer board, and a second inductor that is connected in series between the common terminal and the connection portion, includes a second wiring electrode wound in the predetermined direction, and is provided at an internal layer of the multilayer board. The first and second wiring electrodes at least partially overlap when the multilayer board is viewed in plan.

Acoustic wave filter devices is disclosed. The device includes a piezoelectric layer, an input electrode and an output electrode located on a top surface of the piezoelectric layer and physically separated from one another, and a counter electrode having a top surface connected to a bottom surface of the piezoelectric layer. The input and output electrodes each include a base and at least one extension extending from the base. The at least one extension of the input electrode extending alongside and in a generally opposite direction to and separated by a gap width from an adjacent extension of the at least one extensions of the output electrode. In some embodiments, the at least one extension of the input or output electrodes has a width that can changes from a first end of the at least one extension to a second end.

An acoustic wave filter device is disclosed. The device includes an acoustic wave filter element, and a first resonator and a second resonator coupled to the acoustic wave filter element. The acoustic wave filter element includes interdigited input electrodes and output electrodes located on a top surface of a piezoelectric layer and an counter-electrode on the bottom surface of the piezoelectric layer. Each of the first and the second resonators includes a resonator electrode on the top surface of the piezoelectric layer and a resonator counter-electrode on the bottom surface of the piezoelectric layer. The first resonator has a first notch in resonator impedance at a first frequency. The second resonator includes a first mass loading layer on the second resonator electrode such that the second resonator has a second notch in resonator impedance at a second frequency that is different from the first frequency.

A multiplexer includes: a first bandpass filter having a first end coupled to a common terminal and a second end coupled to a first terminal, the first bandpass filter having a first passband; a second bandpass filter having a first end coupled to the common terminal and a second end coupled to a second terminal, the second bandpass filter having a second passband that does not overlap with the first passband and is higher than the first passband; and a first band-stop filter having a first end coupled to the first terminal and a second end coupled to the second terminal, the first band-stop filter having a first stopband formed of a first attenuation pole and a second attenuation pole, the first attenuation pole being located within the first passband or near the first passband, the second attenuation pole being located within the second passband or near the second passband.

A filter may include a plurality of bulk acoustic wave resonators including one or more series resonators and one or more shunt resonators formed by a first electrode, a piezoelectric layer, and a second electrode sequentially stacked on a substrate, a cap accommodating the plurality of bulk acoustic wave resonators therein, and one or more switches provided on the cap.

A filter may include one or more series unit, and a shunt unit disposed between the one or more series unit and ground. The one or more series unit includes a plurality of series resonators which are selectively operated, and each of the plurality of series resonators includes a film bulk acoustic resonator.

Embodiments of resonator circuits and modulating resonators and are described generally herein. One or more acoustic wave resonators may be coupled in series or parallel to generate tunable filters. One or more acoustic wave resonances may be modulated by one or more capacitors or tunable capacitors. One or more acoustic wave modules may also be switchable in a filter. Other embodiments may be described and claimed.

There is disclosed acoustic resonators and filter devices. An acoustic resonator device includes a piezoelectric plate, a portion of the piezoelectric plate forming a diaphragm, a thickness of the piezoelectric plate is greater than or equal to 300 nm and less than or equal to 500 nm, and an interdigital transducer (IDT) with interleaved fingers of the IDT on the diaphragm. The piezoelectric plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm.