Techniques for improving Bulk Acoustic Wave (BAW) mass loading of resonator structures are disclosed, including filters, oscillators and systems that may include such devices. First and second layers of piezoelectric material may be acoustically coupled with one another to have a piezoelectrically excitable resonance mode. The first layer of piezoelectric material may have a first piezoelectric axis orientation, and the second layer of piezoelectric material may have a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. An acoustic reflector electrode may include a first pair of top metal electrode layers electrically and acoustically coupled with the first and second layer of piezoelectric material to excite the piezoelectrically excitable resonance mode at a resonant frequency of the BAW resonator. The acoustic reflector may include a mass load layer to facilitate a preselected frequency compensation in the resonant frequency.

Techniques for improving Bulk Acoustic Wave (BAW) resonator structures are disclosed, including filters, oscillators and systems that may include such devices. A first layer of piezoelectric material having a piezoelectrically excitable resonance mode may be provided. The first layer of piezoelectric material may have a thickness so that the bulk acoustic wave resonator has a resonant frequency. The first layer of piezoelectric material may include a first pair of sublayers of piezoelectric material, and a first layer of temperature compensating material. A substrate may be provided.

Techniques for improving acoustic wave devices are disclosed, including filters, oscillators and systems that may include such devices. A first piezoelectric layer having a piezoelectrically excitable resonance mode may be provided. A second piezoelectric layer may also be provided. The first piezoelectric layer and the second piezoelectric layer may have respective thicknesses so that the acoustic wave device has a resonant frequency. A temperature compensating layer may be included. A substrate may be provided.

Techniques for improving Bulk Acoustic Wave (BAW) resonator structures are disclosed, including filters, oscillators and systems that may include such devices. A first layer of doped piezoelectric layer material and a second layer of piezoelectric material may be acoustically coupled with one another to have a piezoelectrically excitable resonance mode. The first layer of doped piezoelectric material may have a first piezoelectric axis orientation, and the second layer of piezoelectric material may have a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. An acoustic reflector including a first pair of metal electrode layers may be electrically and acoustically coupled with the first layer of doped piezoelectric material and the second layer of piezoelectric material to excite the piezoelectrically excitable main resonance mode at a resonant frequency.

Techniques for improving acoustic wave device structures are disclosed, including filters and systems that may include such devices. An apparatus may comprise a first electrical filter including an acoustic wave device. The first electrical may having a first filter band in a Super High Frequency (SHF) band or an Extremely High Frequency (EHF) band to facilitate compliance with a regulatory requirement or a standards setting organization specification. For example, the first electrical filter may comprise a notch filter having a notch band overlapping at least a portion of an Earth Exploration Satellite Service (EESS) band to facilitate compliance with a regulatory requirement or the standards setting organization specification for the Earth Exploration Satellite Service (EESS) band.

Embodiments may provide, among other things, a frequency filter including one or more series resonators and one or more shunt resonators. The series resonators may have a first periodicity and the shunt resonators may have a second periodicity. The frequency filter may include a control circuit that may be configured to cause a change in frequency of the one or more series resonators or the one or more shunt resonators of less than the first or second periodicity, respectively, and the change in frequency may result in a change to a passband associated with the frequency filter of at least the first or second periodicity. Additional embodiments may be described and/or claimed herein.

Aspects of this disclosure relate to acoustic wave filters with bulk acoustic wave resonators configured to excite an overtone mode as a main mode. A bulk acoustic wave resonator of the filter can include a plurality of stacked piezoelectric layers positioned between a pair of electrodes.

Aspects of this disclosure relate to an acoustic wave device having an overtone mode as a main mode. The acoustic wave device is sufficiently asymmetric on opposing sides of a piezoelectric layer over an acoustic reflector such that the main mode of the acoustic wave device is the overtone mode.

Techniques for improving acoustic wave device structures are disclosed, including filters and systems that may include such devices. An acoustic wave device may include a substrate. The acoustic wave device may include first and second layers of piezoelectric material acoustically coupled with one another, in which the first layer of piezoelectric material has a first piezoelectric axis orientation, and the second layer of piezoelectric material has a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. The acoustic wave device may include an interposer layer interposed between the first and second layers of piezoelectric material. The interposer may facilitate an enhancement of an electromechanical coupling coefficient of the acoustic wave device.

Techniques for improving acoustic wave device structures are disclosed, including at least filters and systems that may include such devices. An acoustic wave device may include at least a substrate. The acoustic wave device may include at least a first piezoelectric layer and a second piezoelectric layer and a third piezoelectric layer. The second piezoelectric layer may have a second piezoelectric axis orientation. The third piezoelectric layer may have a third piezoelectric axis orientation that substantially opposes the second piezoelectric axis orientation of the second piezoelectric layer. The acoustic wave device may include an interposer layer coupled between the second piezoelectric layer and the third piezoelectric layer.