Resonant Inc.
TRANSVERSELY-EXCITED FILM BULK ACOUSTIC RESONATOR WITH INTERDIGITAL TRANSDUCER WITH VARIED MARK AND PITCH

Abstract:

Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a piezoelectric plate having front and back surfaces and an interdigital transducer (IDT). The IDT has a first pitch/mark zone with interleaved fingers having a pitch equal to a first pitch value P.sub.1 and a mark equal to a first mark value M.sub.1, and a second pitch/mark zone with interleaved fingers having a pitch equal to a second pitch value P.sub.2 and a mark equal to a second mark value M.sub.2. A radio frequency signal applied to the IDT causes excitation of a same shear primary acoustic mode by both the first pitch/mark zone and the second pitch/mark zone. P1, M1, P2, and M2, are selected such that an amplitude of spurious modes is reduced as compared to a device having a same primary acoustic mode and a single pitch/mark zone.