A radio frequency (RF) front-end (RFFE) device includes a die having a front-side dielectric layer on an active device. The active device is on a first substrate. The RFFE device also includes a microelectromechanical system (MEMS) device. The MEMS device is integrated on the die at a different layer than the active device. The MEMS device includes a cap layer composed of a cavity in the front-side dielectric layer of the die. The cavity in the front-side dielectric layer is between the first substrate and a second substrate. The cap is coupled to the front-side dielectric layer.

Embodiments of a single-chip ScAIN tunable filter bank include a plurality of switching elements, and a plurality of channel filters integrated on a monolithic platform. The monolithic platform may comprise a single crystal base and each of the switching elements may comprise at least one of a scandium aluminum nitride (ScAIN) or other Group III-Nitride transistor structure fabricated on the single crystal base. In these embodiments, each channel filter comprises a multi-layered ScAIN structure comprising one or more a single-crystal epitaxial ScAIN layers fabricated on the single crystal base. The ScAIN layers for each channel filter may be based on desired frequency characteristics of an associated one of the RF channels.

A radio frequency filter includes at least a first sub-filter and a second sub-filter connected in parallel between a first port and a second port. Each of the sub-filters has a piezoelectric plate having front and back surfaces, the back surface attached to a substrate, and portions of the piezoelectric plate forming diaphragms spanning respective cavities in the substrate. A conductor pattern is formed on the front surface of the plate, the conductor pattern includes interdigital transducers (IDTs) of a respective plurality of resonators, with interleaved fingers of each IDT disposed on a respective diaphragm of the plurality of diaphragms. A thickness of the portions of the piezoelectric plate of the first sub-filter is different from a thickness of the portions of the piezoelectric plate of the second sub-filter.

A radio frequency filter includes at least a first sub-filter and a second sub-filter connected in parallel between a first port and a second port. Each of the sub-filters has a piezoelectric plate having front and back surfaces, the back surface attached to a substrate, and portions of the piezoelectric plate forming diaphragms spanning respective cavities in the substrate. A conductor pattern is formed on the front surface of the plate, the conductor pattern includes interdigital transducers (IDTs) of a respective plurality of resonators, with interleaved fingers of each IDT disposed on a respective diaphragm of the plurality of diaphragms. A thickness of the portions of the piezoelectric plate of the first sub-filter is different from a thickness of the portions of the piezoelectric plate of the second sub-filter.

Embodiments disclosed herein include resonators and methods of forming such resonators. In an embodiment a resonator comprises a substrate, where a cavity is disposed into a surface of the substrate, and a piezoelectric film suspended over the cavity. In an embodiment, the piezoelectric film has a first surface and a second surface opposite from the first surface, and the piezoelectric film is single crystalline and has a thickness that is 0.5 μm or less. In an embodiment a first electrode is over the first surface of the piezoelectric film, and a second electrode is over the second surface of the piezoelectric film.

Examples provide a wideband filter structure and apparatus, a radio transceiver, a mobile terminal, and a method for filtering a radio signal. The wideband filter structure (10) for a radio signal comprises a combination of at least one acoustic resonator (12) and at least one analog resonator (14). The acoustic resonator (12) is coupled to the analog resonator (14). The wideband filter structure (10) comprises a further component (16), which is coupled to the combination of the acoustic resonator (12) and the analog resonator (14).

A radio-frequency filter (10) includes a series arm resonator (s1) connected between input/output terminals (11m and 11n) and parallel arm circuits (110 and 120) connected to a node (xl) and a ground. The parallel arm circuit (110) includes a parallel arm resonator (p1) and a variable frequency circuit (110A) connected in series with each other between the node (xl) and a ground. The variable frequency circuit (110A) changes the resonant frequency of the parallel arm circuit (110). The variable frequency circuit (110A) is connected in series with the parallel arm resonator (p1) and includes a capacitor (C1) and a switch (SW1) connected in parallel with each other. The parallel arm circuit (120) includes a capacitor (C2) and a switch (SW2) connected in series with each other between the node (x1) and a ground.

Embodiments of a single-chip ScAIN tunable filter bank include a plurality of switching elements, and a plurality of channel filters integrated on a monolithic platform. The monolithic platform may comprise a single crystal base and each of the switching elements may comprise at least one of a scandium aluminum nitride (ScAIN) or other Group III-Nitride transistor structure fabricated on the single crystal base. In these embodiments, each channel filter comprises a multi-layered ScAIN structure comprising one or more a single-crystal epitaxial ScAIN layers fabricated on the single crystal base. The ScAIN layers for each channel filter may be based on desired frequency characteristics of an associated one of the RF channels.

An acoustic resonator structure is provided. The acoustic resonator structure includes an acoustic resonator configured to resonate in a resonance frequency to pass a radio frequency (RF) signal from an input node to an output node. However, the acoustic resonator may create an electrical capacitance in parallel to the acoustic resonator. The electrical capacitance may cause the acoustic resonator to resonate outside the resonance frequency, thus compromising performance of the acoustic resonator. In this regard, an active circuit is provided in parallel to the acoustic resonator in the acoustic resonator structure. The active circuit can be configured to cause a negative capacitance between the input node and the output node. As such, it may be possible to cancel the electrical capacitance created by the acoustic resonator, thus helping to improve performance of the acoustic resonator.

Embodiments may relate to a radio frequency (RF) front-end module (FEM). The RF FEM may include an integrated die with an active portion and an acoustic wave resonator (AWR) portion adjacent to the active portion. The RF FEM may further include a lid coupled with the die. The lid may at least partially overlap the AWR portion at a surface of the die. Other embodiments may be described or claimed.