Transversely-excited bulk acoustic resonator with non-linear chirping profile

An acoustic resonator comprising:

• a piezoelectric layer;
• an interdigital transducer (IDT) on a surface of the piezoelectric layer, the IDT having a plurality of interleaved fingers that alternately extend from a first busbar and a second busbar,
• wherein the IDT comprises a plurality of sections that each have a respective length that includes at least two pairs of interleaved fingers,
• wherein the IDT has an asymmetric chirping profile, such that a variation of at least one of a mark and a pitch of a first section of the plurality of sections is non-linear across the length of the first section, the mark being a width of the at least two pairs of interleaved fingers and the pitch being a center-to-center spacing between each pair of interleaved fingers, and
• wherein the variation of the at least one of the mark and the pitch has a less than 25% effect on a primarily excited main acoustic mode of the acoustic resonator in comparison to a 1:1 effect of at least one of a pitch and a mark on a mode other than the primarily excited main acoustic mode.

An acoustic resonator comprising:

• a piezoelectric layer;
• an interdigital transducer (IDT) on a surface of the piezoelectric layer, the IDT having a plurality of interleaved fingers that alternately extend from a first busbar and a second busbar,
• wherein the IDT comprises a first section and a second section that each have a respective length that includes at least two pairs of interleaved fingers,
• wherein the interleaved fingers of each of the first section and the second section have an asymmetric chirping profile, such that a variation of at least one of a mark and a pitch is non-linear across the length of the respective section, the mark being a width of the at least two pairs of interleaved fingers and the pitch being a center-to-center spacing between each pair of interleaved fingers, and
• wherein the variation of the at least one of the pitch and the mark of each of the first and second sections increases exponentially as the respective length of each of the first and second sections extend towards each other, such that the IDT collectively including the first and second sections has a symmetric chirping profile.