Ultra-wideband mems filters using localized thinned 128 y-cut thin-film lithium niobate

This work demonstrates a first-order antisymmetric Lamb wave ( A1) mode MEMS filter with a fractional bandwidth (FBW) exceeding 24%. Based on the localized thinned 128 degrees Y-cut lithium niobate (LiNbO3) films, the series and shunt A1 mode resonators exhibit excellent effective electromechanical coupling coefficients (k(eff)(2)) of 43.6% and 39.8%, respectively, which is the key to realizing ultra-wideband RF acoustic filters. The fabricated A1 mode filter with a center frequency of 1.79 GHz achieves a minimum insertion loss of 0.61 dB and a maximum 3-dB FBW of 24.6%. After further optimizations, the A1 mode filters will have great potential as broadband acoustic-only filters for 5G New Radio bands.