  Monolithic integration of multiband (1.4~ 6.0 GHz) RF acoustic devices were
successfully demonstrated within the same process flow by using the lithium
niobate (LN) thin film on silicon carbide (LNOSiC) substrate. A novel surface
mode with sinking energy distribution was proposed, exhibiting reduced
propagation loss. Surface wave and Lamb wave resonators with suppressed
transverse modes and leaky modes were demonstrated, showing scalable resonances
from 1.4 to 5.7 GHz, electromechanical coupling coefficients (k2) between 7.9%
and 29.3%, and maximum Bode-Q (Qmax) larger than 3200. Arrayed filters with a
small footprint (4.0 x 2.5 mm2) but diverse center frequencies (fc) and 3-dB
fractional bandwidths (FBW) were achieved, showing fc from 1.4 to 6.0 GHz, FBW
between 3.3% and 13.3%, and insertion loss (IL) between 0.59 and 2.10 dB. These
results may promote the progress of hundred-filter sub-6 GHz RF front-end
modules (RF-FEMs).
