RF360 Singapore Pte. Ltd.

To reduce the effect of ripple caused by reflected waves in a piezoelectric layer, a surface acoustic wave (SAW) resonator employs interdigitated transducer (IDT) fingers that vary in width while maintaining constant finger pitch to shift the frequency response and smooth the ripple in the output signal. A change in width along the IDT finger corresponds to a change in the metallization ratio or loading on the surface of the piezoelectric layer. As the width of the IDT finger changes relative to a default width, the range of the metallization ratio along the finger provides a range of frequency response, including the ripple. The IDT finger has a trapezoidal shape changing width along the length of the finger. The range of the frequency response generated in this manner causes the output signal to be a blend of the range of frequency responses in which the ripple is smoothed.

Techniques and apparatus for designing and fabricating an electroacoustic device. One example method of fabricating an electroacoustic device generally includes forming a layer stack and forming an electrode structure above the layer stack. Forming the layer stack may include forming at least a portion of the layer stack with a thickness based on a positive slope of a function of a metallization ratio of the electrode structure versus the thickness of the at least the portion of the layer stack.

Aspects of the disclosure relate to an apparatus. The apparatus can include a piezoelectric layer including a surface along a surface plane. A plurality of piezoelectric structures extend from the surface in a direction orthogonal to the surface plane. The apparatus can include an electrode layer comprising an electrode disposed on the plurality of piezoelectric structures. wherein the electrode extends along an axis parallel to the surface plane to form at least one finger of an interdigitated transducer (IDT). In some cases, a surface acoustic wave (SAW) filter includes the IDT.

Bare die package with guard to reduce or prevent material seepage into an air cavity, and related fabrication methods. In exemplary aspects, to avoid or reduce material (e.g., an encapsulation material such as a mold material and/or a coating material) from entering or seeping into the air cavity in the active filter region of a filter, the die package includes a guard structure. The guard structure is a structure on or adjacent to the die operable to be used in a filter that redirects or reduces material from entering the gap between the die and the substrate. The guard structure reduces or prevents the material entering the air cavity of the die so as to avoid such material affecting the acoustic performance of the air cavity of the filter.

Aspects are provided for radio frequency (RF) front end modules. The radio frequency front end modules comprises a common antenna node, an antenna switch matrix (ASM) comprising an ASM first signal terminal and at least two ASM second signal terminals, the ASM first signal terminal being coupled with the common antenna node; at least two RF micro acoustic filters coupleable to the common antenna node via the ASM. At least a first RF micro acoustic filter of the at least two RF micro acoustic filters comprises a micro acoustic pre-filter comprising a pre-filter first signal terminal and a pre-filter second signal terminal, the pre-filter first signal terminal coupled with the ASM; and a micro acoustic main-filter comprising a main-filter first signal terminal and a main-filter second signal terminal. The micro acoustic pre-filter and the micro acoustic main-filter being separated by a signal line coupling the pre-filter second signal terminal to the main-filter first signal terminal, the micro acoustic pre-filter being on a different die than the micro acoustic main-filter and being coupled by the signal line.

As the frequencies of microacoustic filter applications increase to address the needs of future technologies, the quality factor Q, which is a measure of energy efficiency, decreases, and the performance of microacoustic filters based on BAW resonators correspondingly decreases. In an exemplary BAW resonator, dielectric layers are disposed on each side of a piezoelectric layer and between the top and bottom electrode layers, which may be formed of metal, to reduce the acoustic/viscous losses that occur in the electrode layers. Inclusion of the bilateral dielectric layers between the top and bottom electrode layers shifts more energy to non-metallic layers to reduce acoustic energy losses. In some examples, a thickness of each of the dielectric layers may be up to thirty percent of a distance between the top and bottom electrode layers.

A surface acoustic wave resonator ( 100 ) comprises a layered substrate including a carrier substrate ( 110 ) and a dielectric layer ( 112 ) having a low acoustic velocity. Another dielectric layer ( 122 ) is disposed on a piezoelectric layer ( 113 ) and interdigitated electrodes ( 131, 132 ) having an acoustic velocity lower than the acoustic velocity of the carrier substrate ( 110 ) and a positive temperature coefficient of frequency.

An apparatus is disclosed for a surface-acoustic-wave device having an Aluminum Nitride substrate layer. In one aspect, a surface acoustic wave (SAW) includes a substrate layer comprising an Aluminum Nitride (AlN) substrate layer, an electrode structure comprising an interdigital transducer, and a piezoelectric layer disposed between the electrode structure and the substrate layer. In some aspects, the piezoelectric layer is Lithium Niobate or Lithium Tantalate.

Aspects include high q resonator devices and associated systems and methods. In one aspect, a device includes first and second busbars. The device includes a first electrode finger coupled to the first busbar and extending in a first direction towards the second busbar without touching the second busbar, where the first electrode finger comprises a finger tip having a first shape, a first stub electrode finger coupled to the second busbar and extending in a second direction opposite the first direction towards the finger tip of the first electrode finger, where the first stub electrode finger comprises a first end coupled to the second busbar and a second end, and where the second end comprises a stub tip having a second shape different than the first shape.

BAW devices include a piezoelectric layer with a first electrode layer on one face and a second electrode layer on the opposite face. The piezoelectric layer and electrode layers determine a coupling efficiency of the BAW devices, which is a measure of the acoustic response of the piezoelectric layer to an input signal. In a BAW device, a first side of the first electrode layer comprises a first material adjacent to a first face of the piezoelectric layer, and a second side of the first electrode layer, opposite to the first face of the piezoelectric layer, comprises a second material, where the first material and the second material have different acoustic impedances. An electrode layer with an acoustic impedance gradient increases the coupling efficiency of the BAW devices.