Systems, acoustic wave structures, and devices

A resonator ladder filter comprising a plurality of acoustic wave resonators electrically coupled to facilitate the resonator ladder filter, in which the plurality of acoustic wave resonators includes at least a first acoustic wave resonator having a main resonant frequency in a millimeter wave band, the first acoustic wave resonator including at least:

• a first electrode;
• a first piezoelectric layer;
• and
• a second piezoelectric layer, in which:
• the first piezoelectric layer has a first piezoelectric axis orientation;
• and
• the second piezoelectric layer has a second piezoelectric axis orientation antiparallel to the first piezoelectric axis orientation.

A wireless communication system comprising:

• a processor;
• a memory;
• and
• an acoustic wave device having a main resonant frequency in a millimeter wave band, in which:
• the wireless communication system is compliant with a standard;
• and
• the acoustic wave device includes at least:
• a first electrode;
• a first piezoelectric layer;
• and
• a second piezoelectric layer, in which the first piezoelectric layer and the second piezoelectric layer are acoustically coupled in a stack.