Wideband RF Filters Using Medium-Scale Integration of Lithium Niobate Laterally Vibrating Resonators

This letter presents wideband spurious-free microelectromechanical systems (MEMSs) filters based on shear horizontal (SH0) mode Lithium Niobate (LiNbO₃) laterally vibrating resonators. The filters, monolithically fabricated on the same chip, have center frequencies at 400 and 750 MHz. The measured performance exhibits in-band ripple-free response, a low insertion loss (IL) of 1.7 dB, a 30-dB shape factor of 1.41, and a 3-dB fractional bandwidth (FBW) of 9.6 %-the largest reported for MEMS-resonator-based filters. The high performance was collaboratively enabled by the LiNbO₃ material and filter design. The excellent piezoelectric coupling and low acoustic loss in LiNbO₃ thin film ensure the low IL and large FBW, while the medium-scale integration of 200 spurious mode-free resonators fully harnesses the potential of LiNbO₃ material without introducing spurious response. The filters have a device footprint less than 360 × 350μm^-2 , thus suitable for RF frontends in handheld wireless devices.