A filter includes two series arm resonators electrically connected in series between two input/output terminals, a parallel arm resonator electrically connected between a ground and a series arm between the two series arm resonators, an inductor electrically connected in parallel to the two series arm resonators, and a matching circuit electrically connected between one of the two series arm resonators and one of the input/output terminals, wherein the two series arm resonators and the parallel arm resonator define a pass band of a bandpass filter, the two series arm resonators and the inductor define an LC resonant circuit, respective anti-resonant frequencies of each of the two series arm resonators and a resonant frequency of the parallel arm resonator are located in a pass band of the LC resonant circuit, and a resonant frequency of the LC resonant circuit is lower than the resonant frequency of the parallel arm resonator.

A resonant member of a MEMS resonator oscillates in a mechanical resonance mode that produces non-uniform regional stresses such that a first level of mechanical stress in a first region of the resonant member is higher than a second level of mechanical stress in a second region of the resonant member. A plurality of openings within a surface of the resonant member are disposed more densely within the first region than the second region and at least partly filled with a compensating material that reduces temperature dependence of the resonant frequency corresponding to the mechanical resonance mode.

A mechanical resonator includes a spring-mass system, wherein the spring-mass system comprises a phase-change material. The mechanical resonator typically comprises an electrical circuit portion, coupled to the phase-change material to alter a phase configuration within the phase-change material. Methods of operation are also disclosed.

A resonance device is provided with a reduced size and also suppresses the occurrence of deformation and breakage during operation. The resonance device includes a lower substrate, an upper substrate that defines a vibration space between the lower substrate and the upper substrate, a protruding portion that is formed on an inner surface of the lower or upper substrates. Moreover, a resonator is disposed in the vibration space and includes a base portion and vibration arms that extend in parallel to one another from the base portion along the inner surface of the lower substrate or the inner surface of the upper substrate and that vibrate in a vertical direction toward the inner surface of the lower substrate or the inner surface of the upper substrate.

A mechanical resonator includes a spring-mass system, wherein the spring-mass system comprises a phase-change material. The mechanical resonator typically comprises an electrical circuit portion, coupled to the phase-change material to alter a phase configuration within the phase-change material. Methods of operation are also disclosed.

A mechanical resonator includes a spring-mass system, wherein the spring-mass system comprises a phase-change material. The mechanical resonator typically comprises an electrical circuit portion, coupled to the phase-change material to alter a phase configuration within the phase-change material. Methods of operation are also disclosed.

A resonant member of a MEMS resonator oscillates in a mechanical resonance mode that produces non-uniform regional stresses such that a first level of mechanical stress in a first region of the resonant member is higher than a second level of mechanical stress in a second region of the resonant member. A plurality of openings within a surface of the resonant member are disposed more densely within the first region than the second region and at least partly filled with a compensating material that reduces temperature dependence of the resonant frequency corresponding to the mechanical resonance mode.

A resonant member of a MEMS resonator oscillates in a mechanical resonance mode that produces non-uniform regional stresses such that a first level of mechanical stress in a first region of the resonant member is higher than a second level of mechanical stress in a second region of the resonant member. A plurality of openings within a surface of the resonant member are disposed more densely within the first region than the second region and at least partly filled with a compensating material that reduces temperature dependence of the resonant frequency corresponding to the mechanical resonance mode.

An apparatus is disclosed for implementing a surface-acoustic-wave (SAW) filter with dielectric material disposed in a piezoelectric layer. In an example aspect, the apparatus includes a surface-acoustic-wave filter with a piezoelectric layer, an electrode structure, and dielectric material. The piezoelectric layer has at least one channel. The dielectric material is disposed in the at least one channel of the piezoelectric layer and is at least partially covered by the electrode structure.