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.

An acoustic structure is provided. The acoustic structure includes an acoustic resonator structure configured to resonate in a series resonance frequency (e.g., passband frequency) to pass a signal, or cause a series capacitance to block the signal in a parallel resonance frequency (e.g., stopband frequency). The parallel resonance frequency may become higher than the series resonance frequency when the tunable capacitance is lesser than or equal to two times of the series capacitance (C.sub.Tune≤2C.sub.0), or lower than the series resonance frequency when the tunable capacitance is greater than two times of the series capacitance (C.sub.Tune>2C.sub.0). In this regard, the acoustic structure can be configured to include a tunable reactive circuit to generate the tunable capacitance (C.sub.Tune) to adjust the parallel resonance frequency. As such, it may be possible to flexibly configure the acoustic resonator structure to block the signal in desired stopband frequencies.

Disclosed is a filter bank module having a substrate, an antenna port terminal, and a filter bank die. The filter bank die is fixed to the substrate and includes a first acoustic wave (AW) filter having a first antenna terminal coupled to the antenna port terminal and a first filter terminal, wherein the first AW filter is configured to pass a first passband and attenuate frequencies outside the first passband, and a second AW filter having a second filter terminal, and a second antenna terminal coupled to the first antenna terminal to effectively diplex signals that pass through the first AW filter and the second AW filter, wherein the second AW filter is configured to pass a second passband that is spaced from the first passband to minimize interference between first bandpass and the second bandpass while attenuating frequencies outside the second passband.

Disclosed is a filter bank die having a first acoustic wave (AW) filter having a first antenna terminal and a first filter terminal, and a second AW filter having a second filter terminal, and a second antenna terminal coupled to the first antenna terminal to effectively diplex signals that pass through the first AW filter and the second AW filter.

A method for determining the state of a piezoelectric element, in particular the piezoelectric element of a sensor apparatus, it is provided. The piezoelectric element is a component of a resonant circuit. The resonant circuit is excited to natural vibrations. The period durations of the natural vibrations of the resonant circuit are captured, and conclusions are drawn regarding the state of the piezoelectric element base on the period durations of the natural vibrations. A sensor apparatus with at least one piezoelectric element is provided. The sensor apparatus has at least one resonant circuit and that the piezoelectric element is a component of the resonant circuit. The sensor apparatus includes at least one evaluator for capturing and evaluating the natural vibrations of the resonant circuit. The evaluator includes at least one storage device for storing reference resonance frequencies that have been determined in advance.

A micro-transfer printable transverse bulk acoustic wave filter comprises a piezoelectric filter element having a top side, a bottom side, a left side, and a right side disposed over a sacrificial portion on a source substrate. A top electrode is in contact with the top side and a bottom electrode is in contact with the bottom side. A left acoustic mirror is in contact with the left side and a right acoustic mirror is in contact with the right side. The thickness of the transverse bulk acoustic wave filter is substantially less than its length or width and its length can be greater than its width. The transverse bulk acoustic wave filter can be disposed on, and electrically connected to, a semiconductor substrate comprising an electronic circuit to control the transverse bulk acoustic wave filter and form a composite heterogeneous device that can be micro-transfer printed.

Embodiments of the invention include a piezoelectric package integrated filtering device that includes a film stack. In one example, the film stack includes a first electrode, a piezoelectric material in contact with the first electrode, and a second electrode in contact with the piezoelectric material. The film stack is suspended with respect to a cavity of an organic substrate having organic material and the film stack generates an acoustic wave to be propagated across the film stack in response to an application of an electrical signal between the first and second electrodes.

Packaged RF front end systems including a hybrid filter and an active circuit in a single package are described. In an example, a package includes an active die comprising an acoustic wave resonator. A package substrate is electrically coupled to the active die. A seal frame surrounds the acoustic wave resonator and is attached to the active die and to the package substrate, the seal frame hermetically sealing the acoustic wave resonator in a cavity between the active die and the package substrate.

A bulk acoustic resonator includes: a substrate including an upper surface on which a substrate protection layer is disposed; and a membrane layer forming a cavity together with the substrate, wherein a thickness deviation of either one or both of the substrate protection layer and the membrane layer is 170 Å or less.

A structure of a semiconductor device is provided, including a circuit substrate. A first metal bulk layer is disposed on the circuit substrate. A buffer layer is disposed on the first metal bulk layer. An absorbing layer is disposed on the buffer layer. A first electrode layer is disposed on the absorbing layer. A plurality of piezoelectric material units are disposed on the first electrode layer. A protection layer is conformally disposed on the piezoelectric material units. A second metal bulk layer is disposed over the piezoelectric material units, and including a first part and a second part. The first part penetrating through the protection layer is disposed on the piezoelectric material units, serving as a second electrode layer. The second part is at a same level of the first part, and at least electrically connecting to the first electrode layer.