Transversely-excited film bulk acoustic filters with symmetric layout

An acoustic resonator, comprising:

• a single-crystal piezoelectric plate having front and back surfaces, the back surface attached to a surface of a substrate except for portions of the piezoelectric plate forming a plurality of diaphragms, each of which spans a respective cavity in the substrate;
• and
• a conductor pattern formed on the front surface, the conductor pattern comprising interdigital transducers (IDTs) of one or more pairs of sub-resonators, wherein
• the IDT of each sub-resonator comprises interleaved fingers disposed over a respective diaphragm,
• the two sub-resonators of each pair of sub-resonators are positioned symmetrically about a central axis, and
• the IDTs of all of the sub-resonators have a common pitch.

A radio frequency filter device comprising:

• a substrate having a surface;
• a single-crystal piezoelectric plate having front and back surfaces, the back surface attached to the surface of the substrate except for portions of the piezoelectric plate forming a plurality of diaphragms, each of which spans a respective cavity in the substrate;
• and
• a conductor pattern formed on the front surface, the conductor pattern defining a ladder filter circuit including a plurality of acoustic resonators, one or more resonators from the plurality of acoustic resonators divided respectively into one or more pairs of sub-resonators, wherein
• each sub-resonator comprises an interdigital transducer (IDT) with interleaved fingers disposed over a diaphragm from the plurality of diaphragms, and the two sub-resonators of each pair of sub-resonators are arranged in symmetrical positions with respect to a central axis of the filter device.